From 126cde00883d0f734b94fce0f8ffeeb45905ada9 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 13 Jun 2026 16:46:30 +0900
Subject: [PATCH v48 5/9] Row pattern recognition patch (executor and
 commands).

---
 src/backend/commands/explain.c        |  484 ++++++
 src/backend/executor/Makefile         |    1 +
 src/backend/executor/execExpr.c       |   92 ++
 src/backend/executor/execExprInterp.c |  267 ++++
 src/backend/executor/execRPR.c        | 1979 +++++++++++++++++++++++++
 src/backend/executor/meson.build      |    1 +
 src/backend/executor/nodeWindowAgg.c  | 1490 ++++++++++++++++---
 src/backend/jit/llvm/llvmjit_expr.c   |   78 +-
 src/backend/jit/llvm/llvmjit_types.c  |    2 +
 src/backend/utils/adt/windowfuncs.c   |  119 +-
 src/include/catalog/pg_proc.dat       |   24 +
 src/include/executor/execExpr.h       |   20 +
 src/include/executor/execRPR.h        |   40 +
 src/include/executor/nodeWindowAgg.h  |    3 +
 src/include/nodes/execnodes.h         |  132 ++
 15 files changed, 4513 insertions(+), 219 deletions(-)
 create mode 100644 src/backend/executor/execRPR.c
 create mode 100644 src/include/executor/execRPR.h

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 112c17b0d64..70fd7f386a0 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -30,6 +30,7 @@
 #include "nodes/extensible.h"
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
+#include "optimizer/rpr.h"
 #include "parser/analyze.h"
 #include "parser/parsetree.h"
 #include "rewrite/rewriteHandler.h"
@@ -119,6 +120,15 @@ static void show_window_def(WindowAggState *planstate,
 static void show_window_keys(StringInfo buf, PlanState *planstate,
 							 int nkeys, AttrNumber *keycols,
 							 List *ancestors, ExplainState *es);
+static void append_rpr_quantifier(StringInfo buf, RPRPatternElement *elem);
+static char *deparse_rpr_pattern(RPRPattern *pattern);
+static int	deparse_rpr_seq(RPRPattern *pattern, int start, int limit,
+							StringInfo buf);
+static int	deparse_rpr_node(RPRPattern *pattern, int i, int limit,
+							 StringInfo buf);
+static int	rpr_match_end(RPRPattern *pattern, int beginIdx);
+static int	rpr_alt_scope_end(RPRPattern *pattern, int i);
+static int	rpr_next_branch(RPRPattern *pattern, int b, int altEnd);
 static void show_storage_info(char *maxStorageType, int64 maxSpaceUsed,
 							  ExplainState *es);
 static void show_tablesample(TableSampleClause *tsc, PlanState *planstate,
@@ -129,6 +139,7 @@ static void show_incremental_sort_info(IncrementalSortState *incrsortstate,
 static void show_hash_info(HashState *hashstate, ExplainState *es);
 static void show_material_info(MaterialState *mstate, ExplainState *es);
 static void show_windowagg_info(WindowAggState *winstate, ExplainState *es);
+static void show_rpr_nfa_stats(WindowAggState *winstate, ExplainState *es);
 static void show_ctescan_info(CteScanState *ctescanstate, ExplainState *es);
 static void show_table_func_scan_info(TableFuncScanState *tscanstate,
 									  ExplainState *es);
@@ -2898,6 +2909,247 @@ show_sortorder_options(StringInfo buf, Node *sortexpr,
 	}
 }
 
+/*
+ * Append quantifier suffix for a pattern element.
+ */
+static void
+append_rpr_quantifier(StringInfo buf, RPRPatternElement *elem)
+{
+	/* Append quantifier if not {1,1} */
+	if (elem->min == 0 && elem->max == RPR_QUANTITY_INF)
+		appendStringInfoChar(buf, '*');
+	else if (elem->min == 1 && elem->max == RPR_QUANTITY_INF)
+		appendStringInfoChar(buf, '+');
+	else if (elem->min == 0 && elem->max == 1)
+		appendStringInfoChar(buf, '?');
+	else if (elem->max == RPR_QUANTITY_INF)
+		appendStringInfo(buf, "{%d,}", elem->min);
+	else if (elem->min == elem->max && elem->min != 1)
+		appendStringInfo(buf, "{%d}", elem->min);
+	else if (elem->min != 1 || elem->max != 1)
+		appendStringInfo(buf, "{%d,%d}", elem->min, elem->max);
+
+	if (RPRElemIsReluctant(elem))
+	{
+		if (elem->min == 1 && elem->max == 1)
+			appendStringInfoString(buf, "{1}"); /* make reluctant ?
+												 * unambiguous */
+		appendStringInfoChar(buf, '?');
+	}
+
+	/* Append absorption markers: " for judgment point, ' for branch only */
+	if (RPRElemIsAbsorbable(elem))
+	{
+		Assert(elem->max == RPR_QUANTITY_INF);
+		appendStringInfoChar(buf, '"');
+	}
+	else if (RPRElemIsAbsorbableBranch(elem))
+		appendStringInfoChar(buf, '\'');
+}
+
+/*
+ * Deparse a compiled RPRPattern (bytecode) back to a pattern string.
+ *
+ * The flat RPRPatternElement[] array is walked by recursive descent.  Each
+ * construct is deparsed within an inherited [start, limit) window: the parent
+ * passes the boundary down, so each construct's extent is fixed by its caller.
+ * Three signals drive the walk:
+ *
+ *   - scope ends (where an ALT or GROUP body finishes) come from depth, via
+ *     rpr_alt_scope_end() and rpr_match_end().
+ *   - branch boundaries (where a "|" goes) come from a branch-start jump,
+ *     confirmed by the relative test elem[j-1].next != j, via
+ *     rpr_next_branch().
+ *   - parentheses come from structure (a BEGIN group, an ALT) plus a one-step
+ *     lookahead for a group that wraps a lone ALT.
+ *
+ * depth and the relative next test are stable across the next/jump values the
+ * compiler assigns to branch tails and nested alternations, which is what makes
+ * them suitable to anchor scope and branch boundaries.
+ *
+ * EXPLAIN parenthesizes every ALT on its own, so a top-level "A | B" deparses
+ * as "(a | b)".  This self-consistent EXPLAIN form is the correctness oracle
+ * here; pg_get_viewdef differs, as its parens come only from an enclosing
+ * GROUP.  Absorption markers (' ") are orthogonal and handled by
+ * append_rpr_quantifier().
+ *
+ * Two compiler invariants hold throughout: {1,1} groups are unwrapped before
+ * bytecode generation (so every BEGIN/END group carries a non-trivial
+ * quantifier, and a lone ALT inside a group always spans to the group's END),
+ * and a group's quantifier is read from its END element (the BEGIN copy is
+ * ignored).
+ */
+static char *
+deparse_rpr_pattern(RPRPattern *pattern)
+{
+	StringInfoData buf;
+
+	Assert(pattern != NULL && pattern->numElements >= 2);
+
+	initStringInfo(&buf);
+	deparse_rpr_seq(pattern, 0, pattern->numElements, &buf);
+	return buf.data;
+}
+
+/*
+ * Deparse a run of sibling elements in [start, limit), separated by spaces.
+ *
+ * Stops at limit or at the FIN terminator (top-level call passes limit =
+ * numElements, where the last element is FIN).  Returns the index reached.
+ */
+static int
+deparse_rpr_seq(RPRPattern *pattern, int start, int limit, StringInfo buf)
+{
+	int			i = start;
+	bool		first = true;
+
+	while (i < limit && !RPRElemIsFin(&pattern->elements[i]))
+	{
+		if (!first)
+			appendStringInfoChar(buf, ' ');
+		first = false;
+		i = deparse_rpr_node(pattern, i, limit, buf);
+	}
+	return i;
+}
+
+/*
+ * Deparse the single construct starting at index i, bounded by the inherited
+ * limit.  Returns the index just past the construct.
+ *
+ * A VAR is its name plus quantifier.  A BEGIN opens a group spanning to its
+ * matching END (rpr_match_end); when the group's sole child is an ALT that
+ * runs to the END, the ALT supplies the parentheses and the group only adds
+ * the quantifier, otherwise the group body is wrapped in its own "( )".  An
+ * ALT runs to its depth-determined scope end (capped by the inherited limit)
+ * and emits "( b1 | b2 | ... )", each branch deparsed within the boundary
+ * handed down by rpr_next_branch.
+ */
+static int
+deparse_rpr_node(RPRPattern *pattern, int i, int limit, StringInfo buf)
+{
+	RPRPatternElement *elem = &pattern->elements[i];
+
+	if (RPRElemIsVar(elem))
+	{
+		Assert(elem->varId < pattern->numVars);
+		appendStringInfoString(buf,
+							   quote_identifier(pattern->varNames[elem->varId]));
+		append_rpr_quantifier(buf, elem);
+		return i + 1;
+	}
+
+	if (RPRElemIsBegin(elem))
+	{
+		int			end = rpr_match_end(pattern, i);
+		bool		loneAlt;
+
+		loneAlt = (i + 1 < end &&
+				   RPRElemIsAlt(&pattern->elements[i + 1]) &&
+				   rpr_alt_scope_end(pattern, i + 1) == end);
+
+		if (loneAlt)
+		{
+			/* The ALT child already parenthesizes the whole group body. */
+			(void) deparse_rpr_node(pattern, i + 1, end, buf);
+		}
+		else
+		{
+			appendStringInfoChar(buf, '(');
+			(void) deparse_rpr_seq(pattern, i + 1, end, buf);
+			appendStringInfoChar(buf, ')');
+		}
+		append_rpr_quantifier(buf, &pattern->elements[end]);
+		return end + 1;
+	}
+
+	Assert(RPRElemIsAlt(elem));
+	{
+		int			altEnd = rpr_alt_scope_end(pattern, i);
+		int			b;
+		bool		first = true;
+
+		if (altEnd > limit)
+			altEnd = limit;
+
+		appendStringInfoChar(buf, '(');
+		b = i + 1;
+		while (b < altEnd)
+		{
+			int			nb = rpr_next_branch(pattern, b, altEnd);
+
+			if (!first)
+				appendStringInfoString(buf, " | ");
+			first = false;
+			(void) deparse_rpr_seq(pattern, b, nb, buf);
+			b = nb;
+		}
+		appendStringInfoChar(buf, ')');
+		return altEnd;
+	}
+}
+
+/*
+ * Find the END that closes the group opened by the BEGIN at beginIdx: the
+ * first END at the same depth scanning forward.
+ */
+static int
+rpr_match_end(RPRPattern *pattern, int beginIdx)
+{
+	RPRDepth	d = pattern->elements[beginIdx].depth;
+	int			j;
+
+	for (j = beginIdx + 1; j < pattern->numElements; j++)
+	{
+		RPRPatternElement *e = &pattern->elements[j];
+
+		if (RPRElemIsEnd(e) && e->depth == d)
+			return j;
+	}
+	pg_unreachable();			/* a BEGIN always has a matching END */
+}
+
+/*
+ * Scope end of the construct at index i: the first following element whose
+ * depth is no greater than i's own.  For an ALT marker this is the index just
+ * past its last branch, since depth stays constant across branch boundaries.
+ * FIN sits at depth 0, so a top-level ALT stops there.
+ */
+static int
+rpr_alt_scope_end(RPRPattern *pattern, int i)
+{
+	RPRDepth	d = pattern->elements[i].depth;
+	int			k;
+
+	for (k = i + 1; k < pattern->numElements; k++)
+	{
+		if (pattern->elements[k].depth <= d)
+			return k;
+	}
+	return pattern->numElements;
+}
+
+/*
+ * Boundary of the alternation branch starting at b (i.e. the start of the next
+ * branch, or altEnd if b is the last branch).
+ *
+ * The branch-start element's jump points at the next branch when this is not
+ * the last branch.  jump is overloaded (a group BEGIN also uses it for its
+ * skip path), so confirm a real branch boundary with the relative test
+ * elem[j-1].next != j: at a true boundary the preceding branch's tail has its
+ * next redirected past the alternation, so it does not point at j.
+ */
+static int
+rpr_next_branch(RPRPattern *pattern, int b, int altEnd)
+{
+	int			j = pattern->elements[b].jump;
+
+	if (j != RPR_ELEMIDX_INVALID && j < altEnd &&
+		pattern->elements[j - 1].next != j)
+		return j;
+	return altEnd;
+}
+
 /*
  * Show the window definition for a WindowAgg node.
  */
@@ -2956,6 +3208,83 @@ show_window_def(WindowAggState *planstate, List *ancestors, ExplainState *es)
 	appendStringInfoChar(&wbuf, ')');
 	ExplainPropertyText("Window", wbuf.data, es);
 	pfree(wbuf.data);
+
+	/* Show Row Pattern Recognition pattern if present */
+	if (wagg->rpPattern != NULL)
+	{
+		char	   *patternStr = deparse_rpr_pattern(wagg->rpPattern);
+
+		if (patternStr != NULL)
+		{
+			ExplainPropertyText("Pattern", patternStr, es);
+			pfree(patternStr);
+		}
+
+		/*
+		 * Show navigation offsets for tuplestore trim.  For EXPLAIN ANALYZE,
+		 * use the executor-resolved values (which may differ from the plan
+		 * when NEEDS_EVAL was resolved to FIXED or RETAIN_ALL at init).
+		 */
+		{
+			RPRNavOffsetKind maxKind = wagg->navMaxOffsetKind;
+			int64		maxOffset = wagg->navMaxOffset;
+			RPRNavOffsetKind firstKind = wagg->navFirstOffsetKind;
+			int64		firstOffset = wagg->navFirstOffset;
+
+			if (es->analyze)
+			{
+				maxKind = planstate->navMaxOffsetKind;
+				maxOffset = planstate->navMaxOffset;
+				firstKind = planstate->navFirstOffsetKind;
+				firstOffset = planstate->navFirstOffset;
+			}
+
+			switch (maxKind)
+			{
+				case RPR_NAV_OFFSET_NEEDS_EVAL:
+					ExplainPropertyText("Nav Mark Lookback", "runtime", es);
+					break;
+				case RPR_NAV_OFFSET_RETAIN_ALL:
+					ExplainPropertyText("Nav Mark Lookback", "retain all", es);
+					break;
+				case RPR_NAV_OFFSET_FIXED:
+					ExplainPropertyInteger("Nav Mark Lookback", NULL,
+										   maxOffset, es);
+					break;
+				default:
+					elog(ERROR, "unrecognized RPR nav offset kind: %d",
+						 maxKind);
+					break;
+			}
+
+			if (wagg->hasFirstNav)
+			{
+				switch (firstKind)
+				{
+					case RPR_NAV_OFFSET_NEEDS_EVAL:
+						ExplainPropertyText("Nav Mark Lookahead", "runtime",
+											es);
+						break;
+					case RPR_NAV_OFFSET_RETAIN_ALL:
+						ExplainPropertyText("Nav Mark Lookahead", "retain all",
+											es);
+						break;
+					case RPR_NAV_OFFSET_FIXED:
+						if (firstOffset == PG_INT64_MAX)
+							ExplainPropertyText("Nav Mark Lookahead", "infinite",
+												es);
+						else
+							ExplainPropertyInteger("Nav Mark Lookahead", NULL,
+												   firstOffset, es);
+						break;
+					default:
+						elog(ERROR, "unrecognized RPR nav offset kind: %d",
+							 firstKind);
+						break;
+				}
+			}
+		}
+	}
 }
 
 /*
@@ -3508,6 +3837,7 @@ show_windowagg_info(WindowAggState *winstate, ExplainState *es)
 {
 	char	   *maxStorageType;
 	int64		maxSpaceUsed;
+	WindowAgg  *wagg = (WindowAgg *) winstate->ss.ps.plan;
 
 	Tuplestorestate *tupstore = winstate->buffer;
 
@@ -3520,6 +3850,160 @@ show_windowagg_info(WindowAggState *winstate, ExplainState *es)
 
 	tuplestore_get_stats(tupstore, &maxStorageType, &maxSpaceUsed);
 	show_storage_info(maxStorageType, maxSpaceUsed, es);
+
+	/* Show NFA statistics for Row Pattern Recognition */
+	if (wagg->rpPattern != NULL)
+		show_rpr_nfa_stats(winstate, es);
+}
+
+/*
+ * Show NFA statistics for Row Pattern Recognition on WindowAgg node.
+ */
+static void
+show_rpr_nfa_stats(WindowAggState *winstate, ExplainState *es)
+{
+	if (es->format != EXPLAIN_FORMAT_TEXT)
+	{
+		/* State and context counters */
+		ExplainPropertyInteger("NFA States Peak", NULL, winstate->nfaStatesMax, es);
+		ExplainPropertyInteger("NFA States Total", NULL, winstate->nfaStatesTotalCreated, es);
+		ExplainPropertyInteger("NFA States Merged", NULL, winstate->nfaStatesMerged, es);
+		ExplainPropertyInteger("NFA Contexts Peak", NULL, winstate->nfaContextsMax, es);
+		ExplainPropertyInteger("NFA Contexts Total", NULL, winstate->nfaContextsTotalCreated, es);
+		ExplainPropertyInteger("NFA Contexts Absorbed", NULL, winstate->nfaContextsAbsorbed, es);
+		ExplainPropertyInteger("NFA Contexts Skipped", NULL, winstate->nfaContextsSkipped, es);
+		ExplainPropertyInteger("NFA Contexts Pruned", NULL, winstate->nfaContextsPruned, es);
+
+		/* Match/mismatch counts and length statistics */
+		ExplainPropertyInteger("NFA Matched", NULL, winstate->nfaMatchesSucceeded, es);
+		ExplainPropertyInteger("NFA Mismatched", NULL, winstate->nfaMatchesFailed, es);
+		if (winstate->nfaMatchesSucceeded > 0)
+		{
+			ExplainPropertyInteger("NFA Match Length Min", NULL, winstate->nfaMatchLen.min, es);
+			ExplainPropertyInteger("NFA Match Length Max", NULL, winstate->nfaMatchLen.max, es);
+			ExplainPropertyFloat("NFA Match Length Avg", NULL,
+								 (double) winstate->nfaMatchLen.total / winstate->nfaMatchesSucceeded, 1,
+								 es);
+		}
+		if (winstate->nfaMatchesFailed > 0)
+		{
+			ExplainPropertyInteger("NFA Mismatch Length Min", NULL, winstate->nfaFailLen.min, es);
+			ExplainPropertyInteger("NFA Mismatch Length Max", NULL, winstate->nfaFailLen.max, es);
+			ExplainPropertyFloat("NFA Mismatch Length Avg", NULL,
+								 (double) winstate->nfaFailLen.total / winstate->nfaMatchesFailed, 1,
+								 es);
+		}
+
+		/* Absorbed/skipped context length statistics */
+		if (winstate->nfaContextsAbsorbed > 0)
+		{
+			ExplainPropertyInteger("NFA Absorbed Length Min", NULL, winstate->nfaAbsorbedLen.min, es);
+			ExplainPropertyInteger("NFA Absorbed Length Max", NULL, winstate->nfaAbsorbedLen.max, es);
+			ExplainPropertyFloat("NFA Absorbed Length Avg", NULL,
+								 (double) winstate->nfaAbsorbedLen.total / winstate->nfaContextsAbsorbed, 1,
+								 es);
+		}
+		if (winstate->nfaContextsSkipped > 0)
+		{
+			ExplainPropertyInteger("NFA Skipped Length Min", NULL, winstate->nfaSkippedLen.min, es);
+			ExplainPropertyInteger("NFA Skipped Length Max", NULL, winstate->nfaSkippedLen.max, es);
+			ExplainPropertyFloat("NFA Skipped Length Avg", NULL,
+								 (double) winstate->nfaSkippedLen.total / winstate->nfaContextsSkipped, 1,
+								 es);
+		}
+	}
+	else
+	{
+		/* State and context counters */
+		ExplainIndentText(es);
+		appendStringInfo(es->str,
+						 "NFA States: " INT64_FORMAT " peak, " INT64_FORMAT " total, " INT64_FORMAT " merged\n",
+						 winstate->nfaStatesMax,
+						 winstate->nfaStatesTotalCreated,
+						 winstate->nfaStatesMerged);
+		ExplainIndentText(es);
+		appendStringInfo(es->str,
+						 "NFA Contexts: " INT64_FORMAT " peak, " INT64_FORMAT " total, " INT64_FORMAT " pruned\n",
+						 winstate->nfaContextsMax,
+						 winstate->nfaContextsTotalCreated,
+						 winstate->nfaContextsPruned);
+
+		/* Match/mismatch counts with length min/max/avg */
+		ExplainIndentText(es);
+		appendStringInfoString(es->str, "NFA: ");
+		if (winstate->nfaMatchesSucceeded > 0)
+		{
+			double		avgLen = (double) winstate->nfaMatchLen.total / winstate->nfaMatchesSucceeded;
+
+			appendStringInfo(es->str,
+							 INT64_FORMAT " matched (len " INT64_FORMAT "/" INT64_FORMAT "/%.1f)",
+							 winstate->nfaMatchesSucceeded,
+							 winstate->nfaMatchLen.min,
+							 winstate->nfaMatchLen.max,
+							 avgLen);
+		}
+		else
+		{
+			appendStringInfoString(es->str, "0 matched");
+		}
+		if (winstate->nfaMatchesFailed > 0)
+		{
+			double		avgFail = (double) winstate->nfaFailLen.total / winstate->nfaMatchesFailed;
+
+			appendStringInfo(es->str,
+							 ", " INT64_FORMAT " mismatched (len " INT64_FORMAT "/" INT64_FORMAT "/%.1f)",
+							 winstate->nfaMatchesFailed,
+							 winstate->nfaFailLen.min,
+							 winstate->nfaFailLen.max,
+							 avgFail);
+		}
+		else
+		{
+			appendStringInfoString(es->str, ", 0 mismatched");
+		}
+		appendStringInfoChar(es->str, '\n');
+
+		/* Absorbed/skipped context length statistics */
+		if (winstate->nfaContextsAbsorbed > 0 || winstate->nfaContextsSkipped > 0)
+		{
+			ExplainIndentText(es);
+			appendStringInfoString(es->str, "NFA: ");
+
+			if (winstate->nfaContextsAbsorbed > 0)
+			{
+				double		avgAbsorbed = (double) winstate->nfaAbsorbedLen.total / winstate->nfaContextsAbsorbed;
+
+				appendStringInfo(es->str,
+								 INT64_FORMAT " absorbed (len " INT64_FORMAT "/" INT64_FORMAT "/%.1f)",
+								 winstate->nfaContextsAbsorbed,
+								 winstate->nfaAbsorbedLen.min,
+								 winstate->nfaAbsorbedLen.max,
+								 avgAbsorbed);
+			}
+			else
+			{
+				appendStringInfoString(es->str, "0 absorbed");
+			}
+
+			if (winstate->nfaContextsSkipped > 0)
+			{
+				double		avgSkipped = (double) winstate->nfaSkippedLen.total / winstate->nfaContextsSkipped;
+
+				appendStringInfo(es->str,
+								 ", " INT64_FORMAT " skipped (len " INT64_FORMAT "/" INT64_FORMAT "/%.1f)",
+								 winstate->nfaContextsSkipped,
+								 winstate->nfaSkippedLen.min,
+								 winstate->nfaSkippedLen.max,
+								 avgSkipped);
+			}
+			else
+			{
+				appendStringInfoString(es->str, ", 0 skipped");
+			}
+
+			appendStringInfoChar(es->str, '\n');
+		}
+	}
 }
 
 /*
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index 11118d0ce02..2b257427795 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -25,6 +25,7 @@ OBJS = \
 	execParallel.o \
 	execPartition.o \
 	execProcnode.o \
+	execRPR.o \
 	execReplication.o \
 	execSRF.o \
 	execScan.o \
diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
index cfea7e160c2..30367825033 100644
--- a/src/backend/executor/execExpr.c
+++ b/src/backend/executor/execExpr.c
@@ -1189,6 +1189,98 @@ ExecInitExprRec(Expr *node, ExprState *state,
 				break;
 			}
 
+		case T_RPRNavExpr:
+			{
+				/*
+				 * RPR navigation functions (PREV/NEXT/FIRST/LAST) are
+				 * compiled into EEOP_RPR_NAV_SET / EEOP_RPR_NAV_RESTORE
+				 * opcodes instead of a normal function call.  The SET opcode
+				 * swaps ecxt_outertuple to the target row, the argument
+				 * expression is compiled normally (reads from the swapped
+				 * slot), and the RESTORE opcode restores the original slot.
+				 *
+				 * Default offset when offset_arg is NULL: PREV/NEXT: 1
+				 * (physical offset from currentpos) FIRST/LAST: 0 (logical
+				 * offset from match boundary)
+				 */
+				RPRNavExpr *nav = (RPRNavExpr *) node;
+				WindowAggState *winstate;
+
+				Assert(state->parent && IsA(state->parent, WindowAggState));
+				winstate = (WindowAggState *) state->parent;
+
+				/* Emit SET opcode: swap slot to target row */
+				scratch.opcode = EEOP_RPR_NAV_SET;
+				scratch.d.rpr_nav.winstate = winstate;
+				scratch.d.rpr_nav.kind = nav->kind;
+
+				if (nav->kind >= RPR_NAV_PREV_FIRST)
+				{
+					/*
+					 * Compound navigation: allocate array of 2 for inner [0]
+					 * and outer [1] offsets.
+					 */
+					Datum	   *offset_values = palloc_array(Datum, 2);
+					bool	   *offset_isnulls = palloc_array(bool, 2);
+
+					/* Inner offset (default 0 for FIRST/LAST) */
+					if (nav->offset_arg != NULL)
+						ExecInitExprRec(nav->offset_arg, state,
+										&offset_values[0], &offset_isnulls[0]);
+					else
+					{
+						offset_values[0] = Int64GetDatum(0);
+						offset_isnulls[0] = false;
+					}
+
+					/* Outer offset (default 1 for PREV/NEXT) */
+					if (nav->compound_offset_arg != NULL)
+						ExecInitExprRec(nav->compound_offset_arg, state,
+										&offset_values[1], &offset_isnulls[1]);
+					else
+					{
+						offset_values[1] = Int64GetDatum(1);
+						offset_isnulls[1] = false;
+					}
+
+					scratch.d.rpr_nav.offset_value = offset_values;
+					scratch.d.rpr_nav.offset_isnull = offset_isnulls;
+				}
+				else if (nav->offset_arg != NULL)
+				{
+					/* Simple navigation with explicit offset */
+					Datum	   *offset_value = palloc_object(Datum);
+					bool	   *offset_isnull = palloc_object(bool);
+
+					ExecInitExprRec(nav->offset_arg, state,
+									offset_value, offset_isnull);
+					scratch.d.rpr_nav.offset_value = offset_value;
+					scratch.d.rpr_nav.offset_isnull = offset_isnull;
+				}
+				else
+				{
+					/* Simple navigation with default offset */
+					scratch.d.rpr_nav.offset_value = NULL;
+					scratch.d.rpr_nav.offset_isnull = NULL;
+				}
+
+				ExprEvalPushStep(state, &scratch);
+
+				/* Compile the argument expression normally */
+				ExecInitExprRec(nav->arg, state, resv, resnull);
+
+				/* Emit RESTORE opcode: restore original slot */
+				scratch.opcode = EEOP_RPR_NAV_RESTORE;
+				scratch.resvalue = resv;
+				scratch.resnull = resnull;
+				scratch.d.rpr_nav.winstate = winstate;
+				get_typlenbyval(nav->resulttype,
+								&scratch.d.rpr_nav.resulttyplen,
+								&scratch.d.rpr_nav.resulttypbyval);
+				ExprEvalPushStep(state, &scratch);
+				break;
+			}
+
 		case T_FuncExpr:
 			{
 				FuncExpr   *func = (FuncExpr *) node;
diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index 0634af964a9..805c8583fb2 100644
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -57,11 +57,13 @@
 #include "postgres.h"
 
 #include "access/heaptoast.h"
+#include "common/int.h"
 #include "access/tupconvert.h"
 #include "catalog/pg_type.h"
 #include "commands/sequence.h"
 #include "executor/execExpr.h"
 #include "executor/nodeSubplan.h"
+#include "executor/nodeWindowAgg.h"
 #include "funcapi.h"
 #include "miscadmin.h"
 #include "nodes/miscnodes.h"
@@ -586,6 +588,8 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		&&CASE_EEOP_WINDOW_FUNC,
 		&&CASE_EEOP_MERGE_SUPPORT_FUNC,
 		&&CASE_EEOP_SUBPLAN,
+		&&CASE_EEOP_RPR_NAV_SET,
+		&&CASE_EEOP_RPR_NAV_RESTORE,
 		&&CASE_EEOP_AGG_STRICT_DESERIALIZE,
 		&&CASE_EEOP_AGG_DESERIALIZE,
 		&&CASE_EEOP_AGG_STRICT_INPUT_CHECK_ARGS,
@@ -2013,6 +2017,24 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			EEO_NEXT();
 		}
 
+		/* RPR navigation: swap slot to target row */
+		EEO_CASE(EEOP_RPR_NAV_SET)
+		{
+			ExecEvalRPRNavSet(state, op, econtext);
+			outerslot = econtext->ecxt_outertuple;
+
+			EEO_NEXT();
+		}
+
+		/* RPR navigation: restore slot to original row */
+		EEO_CASE(EEOP_RPR_NAV_RESTORE)
+		{
+			ExecEvalRPRNavRestore(state, op, econtext);
+			outerslot = econtext->ecxt_outertuple;
+
+			EEO_NEXT();
+		}
+
 		/* evaluate a strict aggregate deserialization function */
 		EEO_CASE(EEOP_AGG_STRICT_DESERIALIZE)
 		{
@@ -5988,3 +6010,248 @@ ExecAggPlainTransByRef(AggState *aggstate, AggStatePerTrans pertrans,
 
 	MemoryContextSwitchTo(oldContext);
 }
+
+/*
+ * Extract compound (outer) offset from step data.
+ * For compound nav, offset_value is an array: [0]=inner, [1]=outer.
+ * Returns the outer offset; errors on NULL or negative.
+ * Default is 1 (like PREV/NEXT implicit offset).
+ */
+static int64
+rpr_nav_get_compound_offset(ExprEvalStep *op)
+{
+	int64		val;
+
+	Assert(op->d.rpr_nav.offset_value != NULL);
+
+	if (op->d.rpr_nav.offset_isnull[1])
+		ereport(ERROR,
+				errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				errmsg("row pattern navigation offset must not be null"));
+
+	val = DatumGetInt64(op->d.rpr_nav.offset_value[1]);
+
+	if (val < 0)
+		ereport(ERROR,
+				errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				errmsg("row pattern navigation offset must not be negative"));
+
+	return val;
+}
+
+/*
+ * Evaluate RPR navigation (PREV/NEXT/FIRST/LAST): swap slot to target row.
+ *
+ * Saves the current outertuple into winstate for later restore, computes
+ * the target row position, fetches the corresponding slot from the
+ * tuplestore, and replaces econtext->ecxt_outertuple with it.
+ *
+ * This is called both from the interpreter inline handler and from
+ * JIT-compiled expressions via build_EvalXFunc.
+ */
+void
+ExecEvalRPRNavSet(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
+{
+	WindowAggState *winstate = op->d.rpr_nav.winstate;
+	int64		offset;
+	int64		target_pos;
+	TupleTableSlot *target_slot;
+
+	/* Save current slot for later restore */
+	winstate->nav_saved_outertuple = econtext->ecxt_outertuple;
+
+	/*
+	 * Determine the inner offset.  NULL or negative offsets are errors per
+	 * the SQL standard.
+	 *
+	 * Default offset when offset_arg is NULL: PREV/NEXT: 1 (standard 5.6.2)
+	 * FIRST/LAST and compound: 0 for inner, 1 for outer
+	 */
+	if (op->d.rpr_nav.offset_value != NULL)
+	{
+		if (*op->d.rpr_nav.offset_isnull)
+			ereport(ERROR,
+					errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					errmsg("row pattern navigation offset must not be null"));
+
+		offset = DatumGetInt64(*op->d.rpr_nav.offset_value);
+
+		if (offset < 0)
+			ereport(ERROR,
+					errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					errmsg("row pattern navigation offset must not be negative"));
+	}
+	else
+	{
+		/* Default offset: 1 for simple PREV/NEXT, 0 otherwise */
+		if (op->d.rpr_nav.kind == RPR_NAV_PREV ||
+			op->d.rpr_nav.kind == RPR_NAV_NEXT)
+			offset = 1;
+		else
+			offset = 0;
+	}
+
+	/*
+	 * Calculate target position based on navigation direction.  On overflow,
+	 * use -1 so that ExecRPRNavGetSlot treats it as out of range.
+	 */
+	switch (op->d.rpr_nav.kind)
+	{
+		case RPR_NAV_PREV:
+			if (pg_sub_s64_overflow(winstate->currentpos, offset, &target_pos))
+				target_pos = -1;
+			break;
+		case RPR_NAV_NEXT:
+			if (pg_add_s64_overflow(winstate->currentpos, offset, &target_pos))
+				target_pos = -1;
+			break;
+		case RPR_NAV_FIRST:
+			/* FIRST: offset from match_start, clamped to currentpos */
+			if (pg_add_s64_overflow(winstate->nav_match_start, offset, &target_pos))
+				target_pos = -1;
+			else if (target_pos > winstate->currentpos)
+				target_pos = -1;	/* beyond current match range */
+			break;
+		case RPR_NAV_LAST:
+			/* LAST: offset backward from currentpos, clamped to match_start */
+			if (pg_sub_s64_overflow(winstate->currentpos, offset, &target_pos))
+				target_pos = -1;
+			else if (target_pos < winstate->nav_match_start)
+				target_pos = -1;	/* before match_start */
+			break;
+
+		case RPR_NAV_PREV_FIRST:
+		case RPR_NAV_NEXT_FIRST:
+			{
+				int64		compound_offset;
+				int64		inner_pos;
+
+				/* Inner: match_start + offset */
+				if (pg_add_s64_overflow(winstate->nav_match_start, offset, &inner_pos))
+				{
+					target_pos = -1;
+					break;
+				}
+				if (inner_pos > winstate->currentpos || inner_pos < 0)
+				{
+					target_pos = -1;
+					break;
+				}
+
+				/* Outer offset */
+				compound_offset = rpr_nav_get_compound_offset(op);
+
+				/* Apply outer: PREV subtracts, NEXT adds */
+				if (op->d.rpr_nav.kind == RPR_NAV_PREV_FIRST)
+				{
+					if (pg_sub_s64_overflow(inner_pos, compound_offset, &target_pos))
+						target_pos = -1;
+				}
+				else
+				{
+					if (pg_add_s64_overflow(inner_pos, compound_offset, &target_pos))
+						target_pos = -1;
+				}
+			}
+			break;
+
+		case RPR_NAV_PREV_LAST:
+		case RPR_NAV_NEXT_LAST:
+			{
+				int64		compound_offset;
+				int64		inner_pos;
+
+				/* Inner: currentpos - offset */
+				if (pg_sub_s64_overflow(winstate->currentpos, offset, &inner_pos))
+				{
+					target_pos = -1;
+					break;
+				}
+				if (inner_pos < winstate->nav_match_start)
+				{
+					target_pos = -1;
+					break;
+				}
+
+				/* Outer offset */
+				compound_offset = rpr_nav_get_compound_offset(op);
+
+				/* Apply outer: PREV subtracts, NEXT adds */
+				if (op->d.rpr_nav.kind == RPR_NAV_PREV_LAST)
+				{
+					if (pg_sub_s64_overflow(inner_pos, compound_offset, &target_pos))
+						target_pos = -1;
+				}
+				else
+				{
+					if (pg_add_s64_overflow(inner_pos, compound_offset, &target_pos))
+						target_pos = -1;
+				}
+			}
+			break;
+		default:
+			elog(ERROR, "unrecognized RPR navigation kind: %d",
+				 op->d.rpr_nav.kind);
+			break;
+	}
+
+	/*
+	 * Slot swap elision: if target_pos is the current row, skip the
+	 * tuplestore fetch and slot swap entirely.  This benefits LAST(expr),
+	 * PREV(expr, 0), NEXT(expr, 0), and similar cases.
+	 *
+	 * We must still set nav_saved_outertuple (done above) so that
+	 * EEOP_RPR_NAV_RESTORE is a harmless no-op.
+	 */
+	if (target_pos == winstate->currentpos)
+		return;
+
+	/* Fetch target row slot (returns nav_null_slot if out of range) */
+	target_slot = ExecRPRNavGetSlot(winstate, target_pos);
+
+	/*
+	 * Update econtext to point to the target slot.  Also decompress the new
+	 * slot's attributes since FETCHSOME already ran for the original slot.
+	 * The caller (interpreter or JIT) is responsible for updating any local
+	 * slot cache (e.g. outerslot) from econtext after we return.
+	 */
+	slot_getallattrs(target_slot);
+	econtext->ecxt_outertuple = target_slot;
+}
+
+/*
+ * Evaluate RPR navigation: restore slot to original row.
+ *
+ * Restores econtext->ecxt_outertuple from the saved slot in winstate.
+ * When slot swap was elided (target == currentpos), this is a harmless
+ * no-op since saved and current slots are identical.
+ * The caller is responsible for updating any local slot cache.
+ *
+ * For pass-by-reference result types, the result datum points into
+ * nav_slot's tuple memory.  If a subsequent navigation in the same
+ * expression re-fetches nav_slot for a different position, the old
+ * tuple is freed, leaving a dangling pointer.  We prevent this by
+ * copying pass-by-ref results into per-tuple memory, which survives
+ * until the next ResetExprContext.
+ */
+void
+ExecEvalRPRNavRestore(ExprState *state, ExprEvalStep *op,
+					  ExprContext *econtext)
+{
+	WindowAggState *winstate = op->d.rpr_nav.winstate;
+
+	econtext->ecxt_outertuple = winstate->nav_saved_outertuple;
+
+	/* Stabilize pass-by-ref result against nav_slot re-fetch */
+	if (!op->d.rpr_nav.resulttypbyval &&
+		!*op->resnull)
+	{
+		MemoryContext oldContext;
+
+		oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
+		*op->resvalue = datumCopy(*op->resvalue,
+								  false,
+								  op->d.rpr_nav.resulttyplen);
+		MemoryContextSwitchTo(oldContext);
+	}
+}
diff --git a/src/backend/executor/execRPR.c b/src/backend/executor/execRPR.c
new file mode 100644
index 00000000000..b326a58bbf5
--- /dev/null
+++ b/src/backend/executor/execRPR.c
@@ -0,0 +1,1979 @@
+/*-------------------------------------------------------------------------
+ *
+ * execRPR.c
+ *	  NFA-based Row Pattern Recognition engine for window functions.
+ *
+ * This file implements the NFA execution engine for the ROWS BETWEEN
+ * PATTERN clause (SQL Standard Feature R020: Row Pattern Recognition in
+ * Window Functions).
+ *
+ * The engine executes the compiled RPRPattern structure directly, avoiding
+ * regex compilation overhead.  It is called by nodeWindowAgg.c and exposes
+ * the interface declared in executor/execRPR.h.
+ *
+ *
+ * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/execRPR.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "common/int.h"
+#include "executor/execRPR.h"
+#include "executor/executor.h"
+#include "miscadmin.h"
+#include "optimizer/rpr.h"
+#include "utils/memutils.h"
+
+/*
+ * For the design and execution model of the NFA engine implemented
+ * in this file, see src/backend/executor/README.rpr.
+ */
+
+/* Bitmap macros for NFA cycle detection (cf. bitmapset.c, tidbitmap.c) */
+#define WORDNUM(x)	((x) / BITS_PER_BITMAPWORD)
+#define BITNUM(x)	((x) % BITS_PER_BITMAPWORD)
+
+/*
+ * Set the visited bit for elemIdx and update the high-water marks
+ * (nfaVisitedMin/MaxWord) so that the next reset only has to clear
+ * the touched range instead of the full nfaVisitedElems bitmap.
+ */
+static inline void
+nfa_mark_visited(WindowAggState *winstate, int16 elemIdx)
+{
+	int16		w = WORDNUM(elemIdx);
+
+	winstate->nfaVisitedElems[w] |= ((bitmapword) 1 << BITNUM(elemIdx));
+	winstate->nfaVisitedMinWord = Min(winstate->nfaVisitedMinWord, w);
+	winstate->nfaVisitedMaxWord = Max(winstate->nfaVisitedMaxWord, w);
+}
+
+/* Forward declarations */
+static RPRNFAState *nfa_state_make(WindowAggState *winstate);
+static void nfa_state_free(WindowAggState *winstate, RPRNFAState *state);
+static void nfa_state_free_list(WindowAggState *winstate, RPRNFAState *list);
+static RPRNFAState *nfa_state_clone(WindowAggState *winstate, int16 elemIdx,
+									int32 *counts, bool sourceAbsorbable);
+static bool nfa_states_equal(WindowAggState *winstate, RPRNFAState *s1,
+							 RPRNFAState *s2);
+static void nfa_add_state_unique(WindowAggState *winstate, RPRNFAContext *ctx,
+								 RPRNFAState *state);
+static void nfa_add_matched_state(WindowAggState *winstate, RPRNFAContext *ctx,
+								  RPRNFAState *state, int64 matchEndRow);
+
+static RPRNFAContext *nfa_context_make(WindowAggState *winstate);
+static void nfa_unlink_context(WindowAggState *winstate, RPRNFAContext *ctx);
+
+static void nfa_update_length_stats(int64 count, NFALengthStats *stats, int64 newLen);
+static void nfa_record_context_skipped(WindowAggState *winstate, int64 skippedLen);
+static void nfa_record_context_absorbed(WindowAggState *winstate, int64 absorbedLen);
+
+static void nfa_update_absorption_flags(RPRNFAContext *ctx);
+static bool nfa_states_covered(RPRPattern *pattern, RPRNFAContext *older,
+							   RPRNFAContext *newer);
+static void nfa_try_absorb_context(WindowAggState *winstate, RPRNFAContext *ctx);
+static void nfa_absorb_contexts(WindowAggState *winstate);
+
+static bool nfa_eval_var_match(WindowAggState *winstate,
+							   RPRPatternElement *elem, bool *varMatched);
+static void nfa_match(WindowAggState *winstate, RPRNFAContext *ctx,
+					  bool *varMatched);
+static void nfa_route_to_elem(WindowAggState *winstate, RPRNFAContext *ctx,
+							  RPRNFAState *state, RPRPatternElement *nextElem,
+							  int64 currentPos);
+static void nfa_advance_alt(WindowAggState *winstate, RPRNFAContext *ctx,
+							RPRNFAState *state, RPRPatternElement *elem,
+							int64 currentPos);
+static void nfa_advance_begin(WindowAggState *winstate, RPRNFAContext *ctx,
+							  RPRNFAState *state, RPRPatternElement *elem,
+							  int64 currentPos);
+static void nfa_advance_end(WindowAggState *winstate, RPRNFAContext *ctx,
+							RPRNFAState *state, RPRPatternElement *elem,
+							int64 currentPos);
+static void nfa_advance_var(WindowAggState *winstate, RPRNFAContext *ctx,
+							RPRNFAState *state, RPRPatternElement *elem,
+							int64 currentPos);
+static void nfa_advance_state(WindowAggState *winstate, RPRNFAContext *ctx,
+							  RPRNFAState *state, int64 currentPos);
+static void nfa_advance(WindowAggState *winstate, RPRNFAContext *ctx,
+						int64 currentPos);
+
+static void nfa_reevaluate_dependent_vars(WindowAggState *winstate,
+										  RPRNFAContext *ctx,
+										  int64 currentPos);
+
+/*
+ * NFA-based pattern matching implementation
+ *
+ * These functions implement direct NFA execution using the compiled
+ * RPRPattern structure, avoiding regex compilation overhead.
+ *
+ * Execution Flow: match -> absorb -> advance
+ * -----------------------------------------
+ * The NFA execution follows a three-phase cycle for each row:
+ *
+ * 1. MATCH (convergence): Evaluate all waiting states against current row.
+ *    States on VAR elements are checked against their defining conditions.
+ *    Failed matches are removed, successful ones may transition forward.
+ *    This is a "convergence" phase - the number of states tends to decrease.
+ *
+ * 2. ABSORB: After matching, check if any context can absorb another.
+ *    Context absorption is an optimization that merges equivalent contexts.
+ *    A context can only be absorbed if ALL its states are absorbable.
+ *
+ * 3. ADVANCE (divergence): Expand states through epsilon transitions.
+ *    States advance through ALT (alternation), END (group end), and
+ *    optional elements until reaching VAR or FIN elements where they wait.
+ *    This is a "divergence" phase - ALT creates multiple branch states.
+ *
+ * Key Design Decisions:
+ * ---------------------
+ * - VAR->END transition in match phase: When a simple VAR (max=1) matches
+ *   and the next element is END, we transition immediately in the match
+ *   phase rather than waiting for advance. This is necessary for correct
+ *   absorption: states must be at END to be marked absorbable before the
+ *   absorption check occurs.
+ *
+ * - Optional VAR skip paths: When advance lands on a VAR with min=0,
+ *   we create both a waiting state AND a skip state (like ALT branches).
+ *   This ensures patterns like "A B? C" work correctly - we need a state
+ *   waiting for B AND a state that has already skipped to C.
+ *
+ * - END->END count increment: When transitioning from one END to another
+ *   END within advance, we must increment the outer END's count. This
+ *   handles nested groups like "((A|B)+)+" correctly - exiting the inner
+ *   group counts as one iteration of the outer group.
+ *
+ * - Empty match handling: The initial advance uses currentPos =
+ *   startPos - 1 (before any row is consumed). If FIN is reached via
+ *   epsilon transitions alone, matchEndRow = startPos - 1 < matchStartRow.
+ *   If matchedState is set (FIN was reached), this is an empty match
+ *   (RF_EMPTY_MATCH); otherwise it is unmatched (RF_UNMATCHED).
+ *   For reluctant min=0 patterns (A*?, A??), the skip path reaches
+ *   FIN first and early termination prunes enter paths, yielding an
+ *   immediate empty match result. For greedy patterns (A*), the enter
+ *   path adds VAR states first, then the skip FIN is recorded but VAR
+ *   states survive for later matching.
+ *
+ * Context Absorption Runtime:
+ * ---------------------------
+ * Absorption uses flags computed at planning time (in rpr.c) and two
+ * context-level flags maintained at runtime:
+ *
+ * State-level:
+ *   state.isAbsorbable: true if state is in the absorbable region.
+ *     - Set at creation: elem->flags & RPR_ELEM_ABSORBABLE_BRANCH
+ *     - At transition: prevAbsorbable && (newElem->flags & ABSORBABLE_BRANCH)
+ *     - Monotonic: once false, stays false forever
+ *
+ * Context-level:
+ *   ctx.hasAbsorbableState: can this context absorb others?
+ *     - True if at least one state has isAbsorbable=true
+ *     - Monotonic: true->false only (optimization: skip recalc when false)
+ *
+ *   ctx.allStatesAbsorbable: can this context be absorbed?
+ *     - True if ALL states have isAbsorbable=true
+ *     - Dynamic: can change false->true (when non-absorbable states die)
+ *
+ * Absorption Algorithm:
+ *   For each pair (older Ctx1, newer Ctx2):
+ *   1. Pre-check: Ctx1.hasAbsorbableState && Ctx2.allStatesAbsorbable
+ *      -> If false, skip (fast filter)
+ *   2. Coverage check: For each Ctx2 state with isAbsorbable=true,
+ *      find Ctx1 state with same elemIdx and count >= Ctx2.count
+ *   3. If all Ctx2 absorbable states are covered, absorb Ctx2
+ *
+ * Example: Pattern A+ B
+ *   Row 1: Ctx1 at A (count=1)
+ *   Row 2: Ctx1 at A (count=2), Ctx2 at A (count=1)
+ *   -> Both at same elemIdx (A), Ctx1.count >= Ctx2.count
+ *   -> Ctx2 absorbed
+ *
+ * The asymmetric design (Ctx1 needs hasAbsorbable, Ctx2 needs allAbsorbable)
+ * allows absorption even when Ctx1 has extra non-absorbable states.
+ */
+
+/*
+ * nfa_state_make
+ *
+ * Allocate an NFA state, reusing from freeList if available.
+ * freeList is stored in WindowAggState for reuse across match attempts.
+ * Uses flexible array member for counts[].
+ */
+static RPRNFAState *
+nfa_state_make(WindowAggState *winstate)
+{
+	RPRNFAState *state;
+
+	/* Try to reuse from free list first */
+	if (winstate->nfaStateFree != NULL)
+	{
+		state = winstate->nfaStateFree;
+		winstate->nfaStateFree = state->next;
+	}
+	else
+	{
+		/* Allocate in partition context for proper lifetime */
+		state = MemoryContextAlloc(winstate->partcontext, winstate->nfaStateSize);
+	}
+
+	/* Initialize entire state to zero */
+	memset(state, 0, winstate->nfaStateSize);
+
+	/* Update statistics */
+	winstate->nfaStatesActive++;
+	winstate->nfaStatesTotalCreated++;
+	winstate->nfaStatesMax = Max(winstate->nfaStatesMax,
+								 winstate->nfaStatesActive);
+
+	return state;
+}
+
+/*
+ * nfa_state_free
+ *
+ * Return a state to the free list for later reuse.
+ */
+static void
+nfa_state_free(WindowAggState *winstate, RPRNFAState *state)
+{
+	winstate->nfaStatesActive--;
+	state->next = winstate->nfaStateFree;
+	winstate->nfaStateFree = state;
+}
+
+/*
+ * nfa_state_free_list
+ *
+ * Return all states in a list to the free list.
+ */
+static void
+nfa_state_free_list(WindowAggState *winstate, RPRNFAState *list)
+{
+	RPRNFAState *next;
+
+	for (; list != NULL; list = next)
+	{
+		next = list->next;
+		nfa_state_free(winstate, list);
+	}
+}
+
+/*
+ * nfa_state_clone
+ *
+ * Clone a state from the given elemIdx and counts.
+ * isAbsorbable is computed immediately: inherited AND new element's flag.
+ * Monotonic property: once false, stays false through all transitions.
+ *
+ * Caller is responsible for linking the returned state.
+ */
+static RPRNFAState *
+nfa_state_clone(WindowAggState *winstate, int16 elemIdx,
+				int32 *counts, bool sourceAbsorbable)
+{
+	RPRPattern *pattern = winstate->rpPattern;
+	int			maxDepth = pattern->maxDepth;
+	RPRNFAState *state = nfa_state_make(winstate);
+	RPRPatternElement *elem = &pattern->elements[elemIdx];
+
+	state->elemIdx = elemIdx;
+	/* Every reachable caller passes a live state's counts; maxDepth >= 1. */
+	Assert(counts != NULL && maxDepth > 0);
+	memcpy(state->counts, counts, sizeof(int32) * maxDepth);
+
+	/*
+	 * Compute isAbsorbable immediately at transition time. isAbsorbable =
+	 * sourceAbsorbable && (elem->flags & ABSORBABLE_BRANCH) Monotonic: once
+	 * false, stays false (can't re-enter absorbable region).
+	 */
+	state->isAbsorbable = sourceAbsorbable && RPRElemIsAbsorbableBranch(elem);
+
+	return state;
+}
+
+/*
+ * nfa_states_equal
+ *
+ * Check if two states are equivalent (same elemIdx and counts).
+ */
+static bool
+nfa_states_equal(WindowAggState *winstate, RPRNFAState *s1, RPRNFAState *s2)
+{
+	RPRPattern *pattern = winstate->rpPattern;
+	RPRPatternElement *elem;
+	int			compareDepth;
+
+	if (s1->elemIdx != s2->elemIdx)
+		return false;
+
+	/*
+	 * Compare counts up to current element's depth.  Two states sharing
+	 * elemIdx are equivalent iff every enclosing-or-current depth count
+	 * matches.
+	 *
+	 * The +1 is the slot arithmetic: comparing through depth N requires
+	 * counts[0..N], i.e., N+1 entries.  Deeper slots (counts[d] with d >
+	 * elem->depth) are excluded because they hold scratch state from inner
+	 * groups.  Per the count-clear policy such a slot is zeroed when its
+	 * owning element exits (see nfa_advance_var and the inline fast path in
+	 * nfa_match), so it must not participate in equivalence judgment.
+	 */
+	elem = &pattern->elements[s1->elemIdx];
+	compareDepth = elem->depth + 1;
+
+	if (memcmp(s1->counts, s2->counts, sizeof(int32) * compareDepth) != 0)
+		return false;
+
+	return true;
+}
+
+/*
+ * nfa_add_state_unique
+ *
+ * Add the state to the end of the ctx->states linked list, but only if a
+ * duplicate state is not already present.
+ * Earlier states have better lexical order (DFS traversal order), so existing
+ * wins; the new state is freed when a duplicate is found.
+ */
+static void
+nfa_add_state_unique(WindowAggState *winstate, RPRNFAContext *ctx, RPRNFAState *state)
+{
+	RPRNFAState *s;
+	RPRNFAState *tail = NULL;
+
+	/*
+	 * Mark VAR in visited before duplicate check to prevent DFS loops. This
+	 * is the deferred half of the asymmetric visited-marking scheme; see
+	 * nfa_advance_state for the non-VAR (END/ALT/BEGIN/FIN) half and the
+	 * rationale for the asymmetry.
+	 */
+	nfa_mark_visited(winstate, state->elemIdx);
+
+	/* Check for duplicate and find tail */
+	for (s = ctx->states; s != NULL; s = s->next)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		if (nfa_states_equal(winstate, s, state))
+		{
+			/*
+			 * Duplicate found - existing has better lexical order, discard
+			 * new
+			 */
+			nfa_state_free(winstate, state);
+			winstate->nfaStatesMerged++;
+			return;
+		}
+		tail = s;
+	}
+
+	/* No duplicate, add at end */
+	state->next = NULL;
+	if (tail == NULL)
+		ctx->states = state;
+	else
+		tail->next = state;
+}
+
+/*
+ * nfa_add_matched_state
+ *
+ * Record a state that reached FIN, replacing any previous match.
+ *
+ * For SKIP PAST LAST ROW, also prune subsequent contexts whose start row
+ * falls within the match range, as they cannot produce output rows.
+ */
+static void
+nfa_add_matched_state(WindowAggState *winstate, RPRNFAContext *ctx,
+					  RPRNFAState *state, int64 matchEndRow)
+{
+	if (ctx->matchedState != NULL)
+		nfa_state_free(winstate, ctx->matchedState);
+
+	ctx->matchedState = state;
+	state->next = NULL;
+	ctx->matchEndRow = matchEndRow;
+
+	/* Prune contexts that started within this match's range */
+	if (winstate->rpSkipTo == ST_PAST_LAST_ROW)
+	{
+		int64		skippedLen;
+
+		while (ctx->next != NULL &&
+			   ctx->next->matchStartRow <= matchEndRow)
+		{
+			RPRNFAContext *nextCtx = ctx->next;
+
+			Assert(nextCtx->lastProcessedRow >= nextCtx->matchStartRow);
+			skippedLen = nextCtx->lastProcessedRow - nextCtx->matchStartRow + 1;
+			nfa_record_context_skipped(winstate, skippedLen);
+
+			ExecRPRFreeContext(winstate, nextCtx);
+		}
+	}
+}
+
+/*
+ * nfa_context_make
+ *
+ * Allocate an NFA context, reusing from free list if available.
+ */
+static RPRNFAContext *
+nfa_context_make(WindowAggState *winstate)
+{
+	RPRNFAContext *ctx;
+
+	if (winstate->nfaContextFree != NULL)
+	{
+		ctx = winstate->nfaContextFree;
+		winstate->nfaContextFree = ctx->next;
+	}
+	else
+	{
+		/* Allocate in partition context for proper lifetime */
+		ctx = MemoryContextAlloc(winstate->partcontext, sizeof(RPRNFAContext));
+	}
+
+	ctx->next = NULL;
+	ctx->prev = NULL;
+	ctx->states = NULL;
+	ctx->matchStartRow = -1;
+	ctx->matchEndRow = -1;
+	ctx->lastProcessedRow = -1;
+	ctx->matchedState = NULL;
+
+	/* Initialize two-flag absorption design based on pattern */
+	ctx->hasAbsorbableState = winstate->rpPattern->isAbsorbable;
+	ctx->allStatesAbsorbable = winstate->rpPattern->isAbsorbable;
+
+	/* Update statistics */
+	winstate->nfaContextsActive++;
+	winstate->nfaContextsTotalCreated++;
+	winstate->nfaContextsMax = Max(winstate->nfaContextsMax,
+								   winstate->nfaContextsActive);
+
+	return ctx;
+}
+
+/*
+ * nfa_unlink_context
+ *
+ * Remove a context from the doubly-linked active context list.
+ * Updates head (nfaContext) and tail (nfaContextTail) as needed.
+ */
+static void
+nfa_unlink_context(WindowAggState *winstate, RPRNFAContext *ctx)
+{
+	if (ctx->prev != NULL)
+		ctx->prev->next = ctx->next;
+	else
+		winstate->nfaContext = ctx->next;	/* was head */
+
+	if (ctx->next != NULL)
+		ctx->next->prev = ctx->prev;
+	else
+		winstate->nfaContextTail = ctx->prev;	/* was tail */
+
+	ctx->next = NULL;
+	ctx->prev = NULL;
+}
+
+/*
+ * nfa_update_length_stats
+ *
+ * Helper function to update min/max/total length statistics.
+ * Called when tracking match/mismatch/absorbed/skipped lengths.
+ */
+static void
+nfa_update_length_stats(int64 count, NFALengthStats *stats, int64 newLen)
+{
+	if (count == 1)
+	{
+		stats->min = newLen;
+		stats->max = newLen;
+	}
+	else
+	{
+		stats->min = Min(stats->min, newLen);
+		stats->max = Max(stats->max, newLen);
+	}
+	stats->total += newLen;
+}
+
+/*
+ * nfa_record_context_skipped
+ *
+ * Record a skipped context in statistics.
+ */
+static void
+nfa_record_context_skipped(WindowAggState *winstate, int64 skippedLen)
+{
+	winstate->nfaContextsSkipped++;
+	nfa_update_length_stats(winstate->nfaContextsSkipped,
+							&winstate->nfaSkippedLen,
+							skippedLen);
+}
+
+/*
+ * nfa_record_context_absorbed
+ *
+ * Record an absorbed context in statistics.
+ */
+static void
+nfa_record_context_absorbed(WindowAggState *winstate, int64 absorbedLen)
+{
+	winstate->nfaContextsAbsorbed++;
+	nfa_update_length_stats(winstate->nfaContextsAbsorbed,
+							&winstate->nfaAbsorbedLen,
+							absorbedLen);
+}
+
+/*
+ * nfa_update_absorption_flags
+ *
+ * Update context's absorption flags after state changes.
+ *
+ * Two flags control absorption behavior:
+ *   hasAbsorbableState: true if context has at least one absorbable state.
+ *     This flag is monotonic (true -> false only). Once all absorbable states
+ *     die, no new absorbable states can be created through transitions.
+ *   allStatesAbsorbable: true if ALL states in context are absorbable.
+ *     This flag is dynamic and can change false -> true when non-absorbable
+ *     states die off.
+ *
+ * Optimization: Once hasAbsorbableState becomes false, both flags remain false
+ * permanently, so we skip recalculation.
+ */
+static void
+nfa_update_absorption_flags(RPRNFAContext *ctx)
+{
+	RPRNFAState *state;
+	bool		hasAbsorbable = false;
+	bool		allAbsorbable = true;
+
+	/*
+	 * Optimization: Once hasAbsorbableState becomes false, it stays false. No
+	 * need to recalculate - both flags remain false permanently.
+	 */
+	if (!ctx->hasAbsorbableState)
+	{
+		ctx->allStatesAbsorbable = false;
+		return;
+	}
+
+	/* No states means no absorbable states */
+	if (ctx->states == NULL)
+	{
+		ctx->hasAbsorbableState = false;
+		ctx->allStatesAbsorbable = false;
+		return;
+	}
+
+	/*
+	 * Iterate through all states to check absorption status. Uses
+	 * state->isAbsorbable which tracks if state is in absorbable region. This
+	 * is different from RPRElemIsAbsorbable(elem) which checks judgment
+	 * point.
+	 */
+	for (state = ctx->states; state != NULL; state = state->next)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		if (state->isAbsorbable)
+			hasAbsorbable = true;
+		else
+			allAbsorbable = false;
+	}
+
+	ctx->hasAbsorbableState = hasAbsorbable;
+	ctx->allStatesAbsorbable = allAbsorbable;
+}
+
+/*
+ * nfa_states_covered
+ *
+ * Check if all states in newer context are "covered" by older context.
+ *
+ * A newer state is covered when older context has an absorbable state at the
+ * same pattern element (elemIdx) with count >= newer's count at that depth.
+ * The covering state must be absorbable because only absorbable states can
+ * guarantee to produce superset matches.
+ *
+ * If all newer states are covered, newer context's eventual matches will be
+ * a subset of older context's matches, making newer redundant.
+ */
+static bool
+nfa_states_covered(RPRPattern *pattern, RPRNFAContext *older, RPRNFAContext *newer)
+{
+	RPRNFAState *newerState;
+
+	for (newerState = newer->states; newerState != NULL; newerState = newerState->next)
+	{
+		RPRNFAState *olderState;
+		RPRPatternElement *elem;
+		int			depth;
+		bool		found = false;
+
+		/* All states are absorbable (caller checks allStatesAbsorbable) */
+		elem = &pattern->elements[newerState->elemIdx];
+		depth = elem->depth;
+
+		/*
+		 * Only compare at absorption judgment points (RPR_ELEM_ABSORBABLE).
+		 * Judgment points are where count-dominance guarantees the newer
+		 * context's future matches are a subset of the older's.
+		 */
+		if (!RPRElemIsAbsorbable(elem))
+			return false;
+
+		for (olderState = older->states; olderState != NULL; olderState = olderState->next)
+		{
+			CHECK_FOR_INTERRUPTS();
+
+			/* Covering state must also be absorbable */
+			if (olderState->isAbsorbable &&
+				olderState->elemIdx == newerState->elemIdx &&
+				olderState->counts[depth] >= newerState->counts[depth])
+			{
+				found = true;
+				break;
+			}
+		}
+
+		if (!found)
+			return false;
+	}
+
+	return true;
+}
+
+/*
+ * nfa_try_absorb_context
+ *
+ * Try to absorb ctx (newer) into an older in-progress context.
+ * Returns true if ctx was absorbed and freed.
+ *
+ * Absorption requires three conditions:
+ *   1. ctx must have all states absorbable (allStatesAbsorbable).
+ *      If ctx has any non-absorbable state, it may produce unique matches.
+ *   2. older must have at least one absorbable state (hasAbsorbableState).
+ *      Without absorbable states, older cannot cover newer's states.
+ *   3. All ctx states must be covered by older's absorbable states.
+ *      This ensures older will produce all matches that ctx would produce.
+ *
+ * Context list is ordered by creation time (oldest first via prev chain).
+ * Each row creates at most one context, so earlier contexts have smaller
+ * matchStartRow values.
+ */
+static void
+nfa_try_absorb_context(WindowAggState *winstate, RPRNFAContext *ctx)
+{
+	RPRPattern *pattern = winstate->rpPattern;
+	RPRNFAContext *older;
+
+	/* Early exit: ctx must have all states absorbable */
+	if (!ctx->allStatesAbsorbable)
+		return;
+
+	for (older = ctx->prev; older != NULL; older = older->prev)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		/*
+		 * By invariant: ctx->prev chain is in creation order (oldest first),
+		 * and each row creates at most one context. So all contexts in this
+		 * chain have matchStartRow < ctx->matchStartRow.
+		 */
+
+		/* Older must also be in-progress */
+		if (older->states == NULL)
+			continue;
+
+		/* Older must have at least one absorbable state */
+		if (!older->hasAbsorbableState)
+			continue;
+
+		/* Check if all newer states are covered by older */
+		if (nfa_states_covered(pattern, older, ctx))
+		{
+			int64		absorbedLen = ctx->lastProcessedRow - ctx->matchStartRow + 1;
+
+			ExecRPRFreeContext(winstate, ctx);
+			nfa_record_context_absorbed(winstate, absorbedLen);
+			return;
+		}
+	}
+}
+
+/*
+ * nfa_absorb_contexts
+ *
+ * Absorb redundant contexts to reduce memory usage and computation.
+ *
+ * For patterns like A+, newer contexts starting later will produce subset
+ * matches of older contexts with higher counts. By absorbing these redundant
+ * contexts early, we avoid duplicate work.
+ *
+ * Iterates from tail (newest) toward head (oldest) via prev chain.
+ * Only in-progress contexts (states != NULL) are candidates for absorption;
+ * completed contexts represent valid match results.
+ */
+static void
+nfa_absorb_contexts(WindowAggState *winstate)
+{
+	RPRNFAContext *ctx;
+	RPRNFAContext *nextCtx;
+
+	for (ctx = winstate->nfaContextTail; ctx != NULL; ctx = nextCtx)
+	{
+		nextCtx = ctx->prev;
+
+		/*
+		 * Only absorb in-progress contexts; completed contexts are valid
+		 * results
+		 */
+		if (ctx->states != NULL)
+			nfa_try_absorb_context(winstate, ctx);
+	}
+}
+
+/*
+ * nfa_eval_var_match
+ *
+ * Evaluate if a VAR element matches the current row.
+ *
+ * varMatched is a pre-evaluated boolean array indexed by varId, computed
+ * once per row by evaluating all DEFINE expressions.  NULL means no DEFINE
+ * clauses exist (only possible during early development/testing).
+ *
+ * Per ISO/IEC 19075-5 Feature R020, pattern variables not listed in DEFINE
+ * are implicitly TRUE -- they match every row.  This is checked via
+ * varId >= list_length.
+ */
+static bool
+nfa_eval_var_match(WindowAggState *winstate, RPRPatternElement *elem,
+				   bool *varMatched)
+{
+	/* This function should only be called for VAR elements */
+	Assert(RPRElemIsVar(elem));
+
+	if (varMatched == NULL)
+		return false;
+	if (elem->varId >= list_length(winstate->defineVariableList))
+		return true;
+	return varMatched[elem->varId];
+}
+
+/*
+ * nfa_match
+ *
+ * Match phase (convergence): evaluate VAR elements against current row.
+ * Only updates counts and removes dead states. Minimal transitions.
+ *
+ * For VAR elements:
+ *   - matched: count++, keep state (unless count > max)
+ *   - not matched: remove state (exit alternatives already exist from
+ *     previous advance when count >= min was satisfied)
+ *
+ * For VARs that reached max count followed by END:
+ *   - Advance through the END-element chain to the absorption judgment point
+ *   - Only deterministic exits (count >= max, max != INF) are handled
+ *   - Chains through END elements while count >= max (must-exit path)
+ *
+ * Non-VAR elements (ALT, END, FIN) are kept as-is for advance phase.
+ */
+static void
+nfa_match(WindowAggState *winstate, RPRNFAContext *ctx, bool *varMatched)
+{
+	RPRPattern *pattern = winstate->rpPattern;
+	RPRPatternElement *elements = pattern->elements;
+	RPRNFAState **prevPtr = &ctx->states;
+	RPRNFAState *state;
+	RPRNFAState *nextState;
+
+	/*
+	 * Evaluate VAR elements against current row. For VARs that reach max
+	 * count with END next, advance through the chain of END elements inline
+	 * so absorb phase can compare states at judgment points.
+	 */
+	for (state = ctx->states; state != NULL; state = nextState)
+	{
+		RPRPatternElement *elem = &elements[state->elemIdx];
+
+		CHECK_FOR_INTERRUPTS();
+
+		nextState = state->next;
+
+		if (RPRElemIsVar(elem))
+		{
+			bool		matched;
+			int			depth = elem->depth;
+			int32		count = state->counts[depth];
+
+			matched = nfa_eval_var_match(winstate, elem, varMatched);
+
+			if (matched)
+			{
+				/* Increment count */
+				if (count < RPR_COUNT_MAX)
+					count++;
+
+				/* Max constraint should not be exceeded */
+				Assert(elem->max == RPR_QUANTITY_INF || count <= elem->max);
+
+				state->counts[depth] = count;
+
+				/*
+				 * For VAR at max count with END next, advance through END
+				 * chain to reach the absorption judgment point.  Only
+				 * deterministic exits (count >= max, max finite) are handled;
+				 * unbounded VARs stay for advance phase.
+				 *
+				 * In nested patterns like ((A B){2}){3}, a VAR reaching its
+				 * max triggers an exit cascade: inner END increments inner
+				 * group count, which may itself reach max, requiring an exit
+				 * to the next outer END.  The loop below walks this chain.
+				 *
+				 * ABSORBABLE_BRANCH marks elements inside the absorbable
+				 * region; ABSORBABLE marks the outermost judgment point where
+				 * count-dominance is evaluated.  We chain through BRANCH
+				 * elements until reaching the ABSORBABLE point or an element
+				 * that can still loop (count < max).
+				 */
+				if (RPRElemIsAbsorbableBranch(elem) &&
+					!RPRElemIsAbsorbable(elem) &&
+					count >= elem->max &&
+					RPRElemIsEnd(&elements[elem->next]))
+				{
+					RPRPatternElement *endElem = &elements[elem->next];
+					int			endDepth = endElem->depth;
+					int32		endCount = state->counts[endDepth];
+
+					/* Increment group count */
+					if (endCount < RPR_COUNT_MAX)
+						endCount++;
+					Assert(endElem->max == RPR_QUANTITY_INF ||
+						   endCount <= endElem->max);
+
+					state->elemIdx = elem->next;
+					state->counts[endDepth] = endCount;
+
+					/*
+					 * Leaf VAR exited (reached max): clear its own count so
+					 * the next occupant enters with zero, as nfa_advance_var
+					 * does on exit (this inline path replaces that exit).
+					 * depth > endDepth, so this leaves the group count just
+					 * written intact.
+					 */
+					Assert(endDepth < depth);
+					state->counts[depth] = 0;
+
+					/*
+					 * Chain through END elements within the absorbable region
+					 * (ABSORBABLE_BRANCH) until reaching the judgment point
+					 * (ABSORBABLE).  Continue only on must-exit path (count
+					 * >= max) with END next.
+					 */
+					while (RPRElemIsAbsorbableBranch(endElem) &&
+						   !RPRElemIsAbsorbable(endElem) &&
+						   endCount >= endElem->max &&
+						   RPRElemIsEnd(&elements[endElem->next]))
+					{
+						RPRPatternElement *outerEnd = &elements[endElem->next];
+						int			outerDepth = outerEnd->depth;
+						int32		outerCount = state->counts[outerDepth];
+
+						/*
+						 * Exit this intermediate group: clear its own count
+						 * (count-clear policy).  It sits below the absorbable
+						 * judgment point, so it is excluded from the
+						 * dominance comparison; the judgment point where the
+						 * chain stops keeps its count.
+						 */
+						state->counts[endDepth] = 0;
+
+						/* Increment outer group count */
+						if (outerCount < RPR_COUNT_MAX)
+							outerCount++;
+						Assert(outerEnd->max == RPR_QUANTITY_INF ||
+							   outerCount <= outerEnd->max);
+
+						state->elemIdx = endElem->next;
+						state->counts[outerDepth] = outerCount;
+
+						/* Advance to next END in chain */
+						endElem = outerEnd;
+						endDepth = outerDepth;
+						endCount = outerCount;
+					}
+				}
+				/* else: stay at VAR for advance phase */
+			}
+			else
+			{
+				/*
+				 * Not matched - remove state. Exit alternatives were already
+				 * created by advance phase when count >= min was satisfied.
+				 */
+				*prevPtr = nextState;
+				nfa_state_free(winstate, state);
+				continue;
+			}
+		}
+		/* Non-VAR elements: keep as-is for advance phase */
+
+		prevPtr = &state->next;
+	}
+}
+
+/*
+ * nfa_route_to_elem
+ *
+ * Route state to next element. If VAR, add to ctx->states and process
+ * skip path if optional. Otherwise, continue epsilon expansion via recursion.
+ */
+static void
+nfa_route_to_elem(WindowAggState *winstate, RPRNFAContext *ctx,
+				  RPRNFAState *state, RPRPatternElement *nextElem,
+				  int64 currentPos)
+{
+	if (RPRElemIsVar(nextElem))
+	{
+		RPRNFAState *skipState = NULL;
+
+		/*
+		 * Entry-side check of the count-clear policy: a VAR is always routed
+		 * to with a clean slot.  Each element zeroes its own count on exit,
+		 * so a nonzero count here would be a leak from an earlier element
+		 * (see nfa_advance_var / nfa_advance_end exit handling and the inline
+		 * fast path in nfa_match).
+		 */
+		Assert(state->counts[nextElem->depth] == 0);
+
+		/* Create skip state before add_unique, which may free state */
+		if (RPRElemCanSkip(nextElem))
+			skipState = nfa_state_clone(winstate, nextElem->next,
+										state->counts, state->isAbsorbable);
+
+		if (skipState != NULL && RPRElemIsReluctant(nextElem))
+		{
+			RPRNFAState *savedMatch = ctx->matchedState;
+
+			/*
+			 * Reluctant optional VAR: prefer skipping.  Explore the skip path
+			 * first so it outranks the enter (match) path; if it reaches FIN
+			 * the shortest match is found and the enter state is dropped.
+			 * This mirrors the reluctant branch of nfa_advance_begin used by
+			 * the leading-position and optional-group paths.
+			 */
+			nfa_advance_state(winstate, ctx, skipState, currentPos);
+
+			if (ctx->matchedState != savedMatch)
+			{
+				nfa_state_free(winstate, state);
+				return;
+			}
+
+			nfa_add_state_unique(winstate, ctx, state);
+		}
+		else
+		{
+			/* Greedy (or non-skippable): enter first, then skip */
+			nfa_add_state_unique(winstate, ctx, state);
+
+			if (skipState != NULL)
+				nfa_advance_state(winstate, ctx, skipState, currentPos);
+		}
+	}
+	else
+	{
+		nfa_advance_state(winstate, ctx, state, currentPos);
+	}
+}
+
+/*
+ * nfa_advance_alt
+ *
+ * Handle ALT element: expand all branches in lexical order via DFS.
+ */
+static void
+nfa_advance_alt(WindowAggState *winstate, RPRNFAContext *ctx,
+				RPRNFAState *state, RPRPatternElement *elem,
+				int64 currentPos)
+{
+	RPRPattern *pattern = winstate->rpPattern;
+	RPRPatternElement *elements = pattern->elements;
+	RPRElemIdx	altIdx = elem->next;
+
+	while (altIdx >= 0)
+	{
+		RPRPatternElement *altElem;
+		RPRNFAState *newState;
+
+		/* Branch jump/next links are always -1 or a valid index */
+		Assert(altIdx < pattern->numElements);
+		altElem = &elements[altIdx];
+
+		/*
+		 * Stop if element is outside ALT scope (not a branch).  The check
+		 * fires when the last branch is a quantified group whose BEGIN.jump
+		 * (set by fillRPRPatternGroup) is preserved -- not overridden by
+		 * fillRPRPatternAlt, which only links non-last branch heads -- and
+		 * leads to a post-ALT element.  Other branch shapes terminate the
+		 * walk earlier via altIdx = RPR_ELEMIDX_INVALID.  Use <=, not <: the
+		 * post-ALT element may sit at the same depth as the ALT when the ALT
+		 * has a sibling at that level.
+		 */
+		if (altElem->depth <= elem->depth)
+			break;
+
+		/* Create independent state for each branch */
+		newState = nfa_state_clone(winstate, altIdx,
+								   state->counts, state->isAbsorbable);
+
+		/* Recursively process this branch before next */
+		nfa_advance_state(winstate, ctx, newState, currentPos);
+		altIdx = altElem->jump;
+	}
+
+	nfa_state_free(winstate, state);
+}
+
+/*
+ * nfa_advance_begin
+ *
+ * Handle BEGIN element: group entry logic.
+ * BEGIN is only visited at initial group entry; loop-back from END goes
+ * directly to first child, bypassing BEGIN.  Per the count-clear policy the
+ * group's own count slot is therefore already zero on entry (asserted below).
+ * If min=0, creates a skip path past the group.
+ */
+static void
+nfa_advance_begin(WindowAggState *winstate, RPRNFAContext *ctx,
+				  RPRNFAState *state, RPRPatternElement *elem,
+				  int64 currentPos)
+{
+	RPRPattern *pattern = winstate->rpPattern;
+	RPRPatternElement *elements = pattern->elements;
+	RPRNFAState *skipState = NULL;
+
+	/*
+	 * Entry-side check of the count-clear policy: the group's own count slot
+	 * is already zero here.  BEGIN is only visited at initial group entry,
+	 * and the previous occupant of this depth slot cleared it on exit.
+	 */
+	Assert(state->counts[elem->depth] == 0);
+
+	/* Optional group: create skip path (but don't route yet) */
+	if (elem->min == 0)
+	{
+		skipState = nfa_state_clone(winstate, elem->jump,
+									state->counts, state->isAbsorbable);
+	}
+
+	if (skipState != NULL && RPRElemIsReluctant(elem))
+	{
+		RPRNFAState *savedMatch = ctx->matchedState;
+
+		/* Reluctant: skip first (prefer fewer iterations), enter second */
+		nfa_route_to_elem(winstate, ctx, skipState,
+						  &elements[elem->jump], currentPos);
+
+		/*
+		 * If skip path reached FIN, shortest match is found. Skip group entry
+		 * to prevent longer matches.
+		 */
+		if (ctx->matchedState != savedMatch)
+		{
+			nfa_state_free(winstate, state);
+			return;
+		}
+
+		state->elemIdx = elem->next;
+		nfa_route_to_elem(winstate, ctx, state,
+						  &elements[state->elemIdx], currentPos);
+	}
+	else
+	{
+		/*
+		 * Greedy-or-non-nullable: route to the first child.  For optional
+		 * groups (skipState != NULL, greedy min=0) additionally create the
+		 * skip path; for non-nullable groups (skipState == NULL, min>0) the
+		 * skip-path action is suppressed by the guard below.
+		 */
+		state->elemIdx = elem->next;
+		nfa_route_to_elem(winstate, ctx, state,
+						  &elements[state->elemIdx], currentPos);
+
+		if (skipState != NULL)
+		{
+			nfa_route_to_elem(winstate, ctx, skipState,
+							  &elements[elem->jump], currentPos);
+		}
+	}
+}
+
+/*
+ * nfa_advance_end
+ *
+ * Handle END element: group repetition logic.
+ * Decides whether to loop back or exit based on count vs min/max.
+ */
+static void
+nfa_advance_end(WindowAggState *winstate, RPRNFAContext *ctx,
+				RPRNFAState *state, RPRPatternElement *elem,
+				int64 currentPos)
+{
+	RPRPattern *pattern = winstate->rpPattern;
+	RPRPatternElement *elements = pattern->elements;
+	int			depth = elem->depth;
+	int32		count = state->counts[depth];
+
+	if (count < elem->min)
+	{
+		RPRPatternElement *jumpElem;
+		RPRNFAState *ffState = NULL;
+		RPRPatternElement *nextElem = NULL;
+
+		/*----------
+		 * Two paths are explored when the group body is nullable
+		 * (RPR_ELEM_EMPTY_LOOP):
+		 *
+		 * 1. Loop-back path: attempt real matches in the next iteration
+		 *    (state, modified below).
+		 *
+		 * 2. Fast-forward path: skip directly to after the group, treating
+		 *    all remaining required iterations as empty matches (ffState).
+		 *    Route to elem->next (not nfa_advance_end) to avoid creating
+		 *    competing greedy/reluctant loop states.
+		 *
+		 * Greedy prefers the loop-back first (more iterations); reluctant
+		 * prefers the fast-forward (exit) first and, if it reaches FIN, drops
+		 * the loop-back so a longer match cannot replace the shortest one --
+		 * mirroring the min<=count<max branch below.  The ffState snapshot is
+		 * taken BEFORE modifying state, since both paths diverge from here.
+		 *----------
+		 */
+		if (RPRElemCanEmptyLoop(elem))
+		{
+			ffState = nfa_state_clone(winstate, state->elemIdx,
+									  state->counts, state->isAbsorbable);
+
+			/* Exit the group: clear its own count (count-clear policy) */
+			ffState->counts[depth] = 0;
+			ffState->elemIdx = elem->next;
+			nextElem = &elements[ffState->elemIdx];
+
+			/*
+			 * Unlike the must-exit path, no isAbsorbable update is needed:
+			 * the fast-forward path runs only for EMPTY_LOOP (nullable)
+			 * groups, which are never inside an absorbable region, so
+			 * isAbsorbable is already false here.
+			 */
+
+			/* END->END: increment outer END's count */
+			if (RPRElemIsEnd(nextElem) &&
+				ffState->counts[nextElem->depth] < RPR_COUNT_MAX)
+				ffState->counts[nextElem->depth]++;
+		}
+
+		/* Prepare the loop-back state */
+		state->elemIdx = elem->jump;
+		jumpElem = &elements[state->elemIdx];
+
+		if (ffState != NULL && RPRElemIsReluctant(elem))
+		{
+			RPRNFAState *savedMatch = ctx->matchedState;
+
+			/* Reluctant: take the fast-forward (exit) first */
+			nfa_route_to_elem(winstate, ctx, ffState, nextElem,
+							  currentPos);
+
+			/*
+			 * If the exit reached FIN, the shortest match is found.  Skip the
+			 * loop-back to prevent longer matches from replacing it.
+			 */
+			if (ctx->matchedState != savedMatch)
+			{
+				nfa_state_free(winstate, state);
+				return;
+			}
+
+			/* Loop-back second */
+			nfa_route_to_elem(winstate, ctx, state, jumpElem,
+							  currentPos);
+		}
+		else
+		{
+			/* Greedy (or non-nullable): loop-back first, fast-forward second */
+			nfa_route_to_elem(winstate, ctx, state, jumpElem,
+							  currentPos);
+			if (ffState != NULL)
+				nfa_route_to_elem(winstate, ctx, ffState, nextElem,
+								  currentPos);
+		}
+	}
+	else if (elem->max != RPR_QUANTITY_INF && count >= elem->max)
+	{
+		/* Must exit: reached max iterations. */
+		RPRPatternElement *nextElem;
+
+		/* Exit: clear the group's own count (count-clear policy) */
+		state->counts[depth] = 0;
+		state->elemIdx = elem->next;
+		nextElem = &elements[state->elemIdx];
+
+		/* Update isAbsorbable for target element (monotonic) */
+		state->isAbsorbable = state->isAbsorbable &&
+			RPRElemIsAbsorbableBranch(nextElem);
+
+		/* END->END: increment outer END's count */
+		if (RPRElemIsEnd(nextElem) && state->counts[nextElem->depth] < RPR_COUNT_MAX)
+			state->counts[nextElem->depth]++;
+
+		nfa_route_to_elem(winstate, ctx, state, nextElem, currentPos);
+	}
+	else
+	{
+		/*
+		 * Between min and max (with at least one iteration) - can exit or
+		 * loop. Greedy: loop first (prefer more iterations). Reluctant: exit
+		 * first (prefer fewer iterations).
+		 */
+		RPRNFAState *exitState;
+		RPRPatternElement *jumpElem;
+		RPRPatternElement *nextElem;
+
+		/*
+		 * Create exit state first (need original counts before modifying
+		 * state)
+		 */
+		exitState = nfa_state_clone(winstate, elem->next,
+									state->counts, state->isAbsorbable);
+		/* Exit branch: clear the group's own count (count-clear policy) */
+		exitState->counts[depth] = 0;
+		nextElem = &elements[exitState->elemIdx];
+
+		/* END->END: increment outer END's count */
+		if (RPRElemIsEnd(nextElem) && exitState->counts[nextElem->depth] < RPR_COUNT_MAX)
+			exitState->counts[nextElem->depth]++;
+
+		/* Prepare loop state */
+		state->elemIdx = elem->jump;
+		jumpElem = &elements[state->elemIdx];
+
+		if (RPRElemIsReluctant(elem))
+		{
+			RPRNFAState *savedMatch = ctx->matchedState;
+
+			/* Exit first (preferred for reluctant) */
+			nfa_route_to_elem(winstate, ctx, exitState, nextElem,
+							  currentPos);
+
+			/*
+			 * If exit path reached FIN, shortest match is found. Skip loop to
+			 * prevent longer matches from replacing it.
+			 */
+			if (ctx->matchedState != savedMatch)
+			{
+				nfa_state_free(winstate, state);
+				return;
+			}
+
+			/* Loop second */
+			nfa_route_to_elem(winstate, ctx, state, jumpElem,
+							  currentPos);
+		}
+		else
+		{
+			/* Loop first (preferred for greedy) */
+			nfa_route_to_elem(winstate, ctx, state, jumpElem,
+							  currentPos);
+			/* Exit second */
+			nfa_route_to_elem(winstate, ctx, exitState, nextElem,
+							  currentPos);
+		}
+	}
+}
+
+/*
+ * nfa_advance_var
+ *
+ * Handle VAR element: loop/exit transitions.
+ * After match phase, all VAR states have matched - decide next action.
+ */
+static void
+nfa_advance_var(WindowAggState *winstate, RPRNFAContext *ctx,
+				RPRNFAState *state, RPRPatternElement *elem,
+				int64 currentPos)
+{
+	RPRPattern *pattern = winstate->rpPattern;
+	RPRPatternElement *elements = pattern->elements;
+	int			depth = elem->depth;
+	int32		count = state->counts[depth];
+	bool		canLoop = (elem->max == RPR_QUANTITY_INF || count < elem->max);
+	bool		canExit = (count >= elem->min);
+
+	/* min <= max, so !canExit (count < min) implies canLoop (count < max) */
+	Assert(canLoop || canExit);
+
+	/* elem->next must be a valid index for any reachable VAR */
+	Assert(elem->next >= 0 && elem->next < pattern->numElements);
+
+	if (canLoop && canExit)
+	{
+		/*
+		 * Both loop and exit possible. Greedy: loop first (prefer longer
+		 * match). Reluctant: exit first (prefer shorter match).
+		 */
+		RPRNFAState *cloneState;
+		RPRPatternElement *nextElem;
+		bool		reluctant = RPRElemIsReluctant(elem);
+
+		/*
+		 * Clone state for the first-priority path. For greedy, clone is the
+		 * loop state; for reluctant, clone is the exit state.
+		 */
+		if (reluctant)
+		{
+			RPRNFAState *savedMatch = ctx->matchedState;
+
+			/* Clone for exit, original stays for loop */
+			cloneState = nfa_state_clone(winstate, elem->next,
+										 state->counts, state->isAbsorbable);
+			/* Exit: clear the VAR's own count (count-clear policy) */
+			cloneState->counts[depth] = 0;
+			nextElem = &elements[cloneState->elemIdx];
+
+			/* When exiting directly to an outer END, increment its count */
+			if (RPRElemIsEnd(nextElem))
+			{
+				if (cloneState->counts[nextElem->depth] < RPR_COUNT_MAX)
+					cloneState->counts[nextElem->depth]++;
+			}
+
+			/* Exit first (preferred for reluctant) */
+			nfa_route_to_elem(winstate, ctx, cloneState, nextElem,
+							  currentPos);
+
+			/*
+			 * If exit path reached FIN, the shortest match is found. Skip
+			 * loop state to prevent longer matches from replacing it.
+			 */
+			if (ctx->matchedState != savedMatch)
+			{
+				nfa_state_free(winstate, state);
+				return;
+			}
+
+			/* Loop second */
+			nfa_add_state_unique(winstate, ctx, state);
+		}
+		else
+		{
+			/* Clone for loop, original used for exit */
+			cloneState = nfa_state_clone(winstate, state->elemIdx,
+										 state->counts, state->isAbsorbable);
+
+			/* Loop first (preferred for greedy) */
+			nfa_add_state_unique(winstate, ctx, cloneState);
+
+			/* Exit second: clear the VAR's own count (count-clear policy) */
+			state->counts[depth] = 0;
+			state->elemIdx = elem->next;
+			nextElem = &elements[state->elemIdx];
+
+			/*
+			 * Update isAbsorbable for target element (monotonic: AND
+			 * preserves false)
+			 */
+			state->isAbsorbable = state->isAbsorbable &&
+				RPRElemIsAbsorbableBranch(nextElem);
+
+			/*
+			 * When exiting directly to an outer END, increment its iteration
+			 * count.  Simple VARs (min=max=1) handle this via inline advance
+			 * in nfa_match, but quantified VARs bypass that path.
+			 */
+			if (RPRElemIsEnd(nextElem))
+			{
+				if (state->counts[nextElem->depth] < RPR_COUNT_MAX)
+					state->counts[nextElem->depth]++;
+			}
+
+			nfa_route_to_elem(winstate, ctx, state, nextElem,
+							  currentPos);
+		}
+	}
+	else if (canLoop)
+	{
+		/* Loop only: keep state as-is */
+		nfa_add_state_unique(winstate, ctx, state);
+	}
+	else
+	{
+		/* Exit only: advance to next element (canExit necessarily true) */
+		RPRPatternElement *nextElem;
+
+		Assert(canExit);
+		/* Exit: clear the VAR's own count (count-clear policy) */
+		state->counts[depth] = 0;
+		state->elemIdx = elem->next;
+		nextElem = &elements[state->elemIdx];
+
+		/*
+		 * Update isAbsorbable for target element (monotonic: AND preserves
+		 * false)
+		 */
+		state->isAbsorbable = state->isAbsorbable &&
+			RPRElemIsAbsorbableBranch(nextElem);
+
+		/* See comment above: increment outer END count for quantified VARs */
+		if (RPRElemIsEnd(nextElem))
+		{
+			if (state->counts[nextElem->depth] < RPR_COUNT_MAX)
+				state->counts[nextElem->depth]++;
+		}
+
+		nfa_route_to_elem(winstate, ctx, state, nextElem, currentPos);
+	}
+}
+
+/*
+ * nfa_advance_state
+ *
+ * Recursively process a single state through epsilon transitions.
+ * DFS traversal ensures states are added to ctx->states in lexical order.
+ */
+static void
+nfa_advance_state(WindowAggState *winstate, RPRNFAContext *ctx,
+				  RPRNFAState *state, int64 currentPos)
+{
+	RPRPattern *pattern = winstate->rpPattern;
+	RPRPatternElement *elem;
+
+	Assert(state->elemIdx >= 0 && state->elemIdx < pattern->numElements);
+
+	/* Protect against stack overflow for deeply complex patterns */
+	check_stack_depth();
+
+	/* Cycle detection: if this elemIdx was already visited in this DFS, bail */
+	if (winstate->nfaVisitedElems[WORDNUM(state->elemIdx)] &
+		((bitmapword) 1 << BITNUM(state->elemIdx)))
+	{
+		nfa_state_free(winstate, state);
+		return;
+	}
+
+	elem = &pattern->elements[state->elemIdx];
+
+	/*
+	 * Mark epsilon elements (END, ALT, BEGIN, FIN) in visited to prevent
+	 * infinite epsilon cycles.  VAR elements are marked later when added to
+	 * the state list (nfa_add_state_unique), allowing legitimate loop-back to
+	 * the same VAR in a new iteration.
+	 */
+	if (!RPRElemIsVar(elem))
+		nfa_mark_visited(winstate, state->elemIdx);
+
+	switch (elem->varId)
+	{
+		case RPR_VARID_FIN:
+			/* FIN: record match */
+			nfa_add_matched_state(winstate, ctx, state, currentPos);
+			break;
+
+		case RPR_VARID_ALT:
+			nfa_advance_alt(winstate, ctx, state, elem, currentPos);
+			break;
+
+		case RPR_VARID_BEGIN:
+			nfa_advance_begin(winstate, ctx, state, elem, currentPos);
+			break;
+
+		case RPR_VARID_END:
+			nfa_advance_end(winstate, ctx, state, elem, currentPos);
+			break;
+
+		default:
+			/* VAR element */
+			nfa_advance_var(winstate, ctx, state, elem, currentPos);
+			break;
+	}
+}
+
+/*
+ * nfa_advance
+ *
+ * Advance phase (divergence): transition from all surviving states.
+ * Called after match phase with matched VAR states, or at context creation
+ * for initial epsilon expansion (with currentPos = startPos - 1).
+ *
+ * Processes states in order, using recursive DFS to maintain lexical order.
+ */
+static void
+nfa_advance(WindowAggState *winstate, RPRNFAContext *ctx, int64 currentPos)
+{
+	RPRNFAState *states = ctx->states;
+	RPRNFAState *state;
+	RPRNFAState *savedMatchedState;
+
+	ctx->states = NULL;			/* Will rebuild */
+
+	/* Process each state in lexical order (DFS order from previous advance) */
+	while (states != NULL)
+	{
+		CHECK_FOR_INTERRUPTS();
+		savedMatchedState = ctx->matchedState;
+
+		/*
+		 * Clear visited bitmap before each state's DFS expansion.  Only the
+		 * range touched since the previous reset (tracked via the high-water
+		 * marks updated in nfa_mark_visited) needs to be cleared; for small
+		 * NFAs this is the whole array, but for large NFAs whose DFS only
+		 * reaches a few elements per advance it avoids walking the full
+		 * bitmap.
+		 */
+		if (winstate->nfaVisitedMaxWord >= winstate->nfaVisitedMinWord)
+		{
+			memset(&winstate->nfaVisitedElems[winstate->nfaVisitedMinWord], 0,
+				   sizeof(bitmapword) *
+				   (winstate->nfaVisitedMaxWord -
+					winstate->nfaVisitedMinWord + 1));
+			winstate->nfaVisitedMinWord = PG_INT16_MAX;
+			winstate->nfaVisitedMaxWord = -1;
+		}
+
+		state = states;
+		states = states->next;
+
+		/*
+		 * Boundary contract: state->next is reset to NULL here, before
+		 * crossing into nfa_advance_state's epsilon-expansion DFS.  The inner
+		 * branches (nfa_advance_var, nfa_advance_begin/end/alt) treat
+		 * state->next as already-NULL and don't reset it themselves; the
+		 * other linking site is nfa_add_state_unique, which sets it when
+		 * appending to ctx->states.
+		 */
+		state->next = NULL;
+
+		nfa_advance_state(winstate, ctx, state, currentPos);
+
+		/*
+		 * Early termination: if a FIN was newly reached in this advance,
+		 * remaining old states have worse lexical order and can be pruned.
+		 * Only check for new FIN arrivals (not ones from previous rows).
+		 */
+		if (ctx->matchedState != savedMatchedState && states != NULL)
+		{
+			nfa_state_free_list(winstate, states);
+			break;
+		}
+	}
+}
+
+/*
+ * nfa_reevaluate_dependent_vars
+ *		Re-evaluate match_start-dependent DEFINE variables for a specific
+ *		context whose matchStartRow differs from the shared evaluation's
+ *		nav_match_start.
+ *
+ * Only variables in defineMatchStartDependent are re-evaluated.  The
+ * current row's slot (ecxt_outertuple) must already be set up by
+ * nfa_evaluate_row().
+ */
+static void
+nfa_reevaluate_dependent_vars(WindowAggState *winstate, RPRNFAContext *ctx,
+							  int64 currentPos)
+{
+	ExprContext *econtext = winstate->ss.ps.ps_ExprContext;
+	int64		saved_match_start = winstate->nav_match_start;
+	int64		saved_pos = winstate->currentpos;
+
+	/* Temporarily set nav_match_start and currentpos for FIRST/LAST */
+	winstate->nav_match_start = ctx->matchStartRow;
+	winstate->currentpos = currentPos;
+
+	/* Invalidate nav_slot cache since match_start changed */
+	winstate->nav_slot_pos = -1;
+
+	foreach_ptr(ExprState, exprState, winstate->defineClauseList)
+	{
+		int			varIdx = foreach_current_index(exprState);
+
+		if (bms_is_member(varIdx, winstate->defineMatchStartDependent))
+		{
+			Datum		result;
+			bool		isnull;
+
+			result = ExecEvalExpr(exprState, econtext, &isnull);
+			winstate->nfaVarMatched[varIdx] = (!isnull && DatumGetBool(result));
+		}
+
+		if (varIdx + 1 >= list_length(winstate->defineVariableList))
+			break;
+	}
+
+	/* Restore original match_start, currentpos, and invalidate cache */
+	winstate->nav_match_start = saved_match_start;
+	winstate->currentpos = saved_pos;
+	winstate->nav_slot_pos = -1;
+}
+
+
+/***********************************************************************
+ * API exposed to nodeWindowAgg.c
+ ***********************************************************************/
+
+/*
+ * ExecRPRStartContext
+ *
+ * Start a new match context at given position.
+ * Initializes context, state absorption flags, and performs initial advance
+ * to expand epsilon transitions (ALT branches, optional elements).
+ * Adds context to the tail of winstate->nfaContext list.
+ */
+RPRNFAContext *
+ExecRPRStartContext(WindowAggState *winstate, int64 startPos)
+{
+	RPRNFAContext *ctx;
+	RPRPattern *pattern = winstate->rpPattern;
+	RPRPatternElement *elem;
+
+	ctx = nfa_context_make(winstate);
+	ctx->matchStartRow = startPos;
+	ctx->states = nfa_state_make(winstate); /* initial state at elem 0 */
+
+	elem = &pattern->elements[0];
+
+	if (RPRElemIsAbsorbableBranch(elem))
+	{
+		ctx->states->isAbsorbable = true;
+	}
+	else
+	{
+		ctx->hasAbsorbableState = false;
+		ctx->allStatesAbsorbable = false;
+		ctx->states->isAbsorbable = false;
+	}
+
+	/* Add to tail of active context list (doubly-linked, oldest-first) */
+	ctx->prev = winstate->nfaContextTail;
+	ctx->next = NULL;
+	if (winstate->nfaContextTail != NULL)
+		winstate->nfaContextTail->next = ctx;
+	else
+		winstate->nfaContext = ctx; /* first context becomes head */
+	winstate->nfaContextTail = ctx;
+
+	/*
+	 * Initial advance (divergence): expand ALT branches and create exit
+	 * states for VAR elements with min=0. This prepares the context for the
+	 * first row's match phase.
+	 *
+	 * Use startPos - 1 as currentPos since no row has been consumed yet. If
+	 * FIN is reached via epsilon transitions, matchEndRow = startPos - 1
+	 * which is less than matchStartRow, resulting in UNMATCHED treatment.
+	 */
+	nfa_advance(winstate, ctx, startPos - 1);
+
+	return ctx;
+}
+
+/*
+ * ExecRPRGetHeadContext
+ *
+ * Return the head context if its start position matches pos.
+ * Returns NULL if no context exists or head doesn't match pos.
+ */
+RPRNFAContext *
+ExecRPRGetHeadContext(WindowAggState *winstate, int64 pos)
+{
+	RPRNFAContext *ctx = winstate->nfaContext;
+
+	/*
+	 * Contexts are sorted by matchStartRow ascending.  If the head context
+	 * doesn't match pos, no context exists for this position.
+	 */
+	if (ctx == NULL || ctx->matchStartRow != pos)
+		return NULL;
+
+	return ctx;
+}
+
+/*
+ * ExecRPRFreeContext
+ *
+ * Unlink context from active list and return it to free list.
+ * Also frees any states in the context.
+ */
+void
+ExecRPRFreeContext(WindowAggState *winstate, RPRNFAContext *ctx)
+{
+	/* Unlink from active list first */
+	nfa_unlink_context(winstate, ctx);
+
+	/* Update statistics */
+	winstate->nfaContextsActive--;
+
+	if (ctx->states != NULL)
+		nfa_state_free_list(winstate, ctx->states);
+	if (ctx->matchedState != NULL)
+		nfa_state_free(winstate, ctx->matchedState);
+
+	ctx->states = NULL;
+	ctx->matchedState = NULL;
+	ctx->next = winstate->nfaContextFree;
+	winstate->nfaContextFree = ctx;
+}
+
+/*
+ * ExecRPRRecordContextSuccess
+ *
+ * Record a successful context in statistics.
+ */
+void
+ExecRPRRecordContextSuccess(WindowAggState *winstate, int64 matchLen)
+{
+	winstate->nfaMatchesSucceeded++;
+	nfa_update_length_stats(winstate->nfaMatchesSucceeded,
+							&winstate->nfaMatchLen,
+							matchLen);
+}
+
+/*
+ * ExecRPRRecordContextFailure
+ *
+ * Record a failed context in statistics.
+ * If failedLen == 1, count as pruned (failed on first row).
+ * If failedLen > 1, count as mismatched and update length stats.
+ */
+void
+ExecRPRRecordContextFailure(WindowAggState *winstate, int64 failedLen)
+{
+	if (failedLen == 1)
+	{
+		winstate->nfaContextsPruned++;
+	}
+	else
+	{
+		winstate->nfaMatchesFailed++;
+		nfa_update_length_stats(winstate->nfaMatchesFailed,
+								&winstate->nfaFailLen,
+								failedLen);
+	}
+}
+
+/*
+ * ExecRPRProcessRow
+ *
+ * Process all contexts for one row:
+ *   1. Match all contexts (convergence) - evaluate VARs, prune dead states
+ *   2. Absorb redundant contexts - ideal timing after convergence
+ *   3. Advance all contexts (divergence) - create new states for next row
+ */
+void
+ExecRPRProcessRow(WindowAggState *winstate, int64 currentPos,
+				  bool hasLimitedFrame, int64 frameOffset)
+{
+	RPRNFAContext *ctx;
+	bool	   *varMatched = winstate->nfaVarMatched;
+	bool		hasDependent = !bms_is_empty(winstate->defineMatchStartDependent);
+
+	/* Allow query cancellation once per row for simple/low-state patterns */
+	CHECK_FOR_INTERRUPTS();
+
+	/*
+	 * Phase 1: Match all contexts (convergence).  Evaluate VAR elements,
+	 * update counts, remove dead states.
+	 */
+	for (ctx = winstate->nfaContext; ctx != NULL; ctx = ctx->next)
+	{
+		if (ctx->states == NULL)
+			continue;
+
+		/* Check frame boundary - finalize the context when it is reached */
+		if (hasLimitedFrame)
+		{
+			int64		ctxFrameEnd;
+
+			/*
+			 * Clamp to PG_INT64_MAX on overflow.  frameOffset can be as large
+			 * as PG_INT64_MAX (e.g. "ROWS <huge> FOLLOWING"), so add the
+			 * offset and the trailing +1 in two separately checked steps to
+			 * avoid signed-integer overflow in the "frameOffset + 1"
+			 * subexpression.
+			 */
+			if (pg_add_s64_overflow(ctx->matchStartRow, frameOffset,
+									&ctxFrameEnd) ||
+				pg_add_s64_overflow(ctxFrameEnd, 1, &ctxFrameEnd))
+				ctxFrameEnd = PG_INT64_MAX;
+
+			/*
+			 * currentPos advances by exactly one per call, and a finalized
+			 * context is skipped by the states == NULL guard above, so it can
+			 * only ever reach ctxFrameEnd, never overshoot it.  The Assert
+			 * turns a future change that broke that invariant into an
+			 * immediate failure rather than a silent slip past the boundary.
+			 */
+			Assert(currentPos <= ctxFrameEnd);
+
+			if (currentPos == ctxFrameEnd)
+			{
+				/* Frame boundary reached: force mismatch */
+				nfa_match(winstate, ctx, NULL);
+				continue;
+			}
+		}
+
+		/*
+		 * If this context has a different matchStartRow than the one used in
+		 * the shared evaluation, re-evaluate match_start-dependent variables
+		 * with this context's matchStartRow.
+		 */
+		if (hasDependent && ctx->matchStartRow != winstate->nav_match_start)
+			nfa_reevaluate_dependent_vars(winstate, ctx, currentPos);
+		nfa_match(winstate, ctx, varMatched);
+		ctx->lastProcessedRow = currentPos;
+	}
+
+	/*
+	 * Phase 2: Absorb redundant contexts.  After match phase, states have
+	 * converged - ideal for absorption.  First update absorption flags that
+	 * may have changed due to state removal.
+	 */
+	if (winstate->rpPattern->isAbsorbable)
+	{
+		for (ctx = winstate->nfaContext; ctx != NULL; ctx = ctx->next)
+			nfa_update_absorption_flags(ctx);
+
+		nfa_absorb_contexts(winstate);
+	}
+
+	/*
+	 * Phase 3: Advance all contexts (divergence).  Create new states
+	 * (loop/exit) from surviving matched states.
+	 */
+	for (ctx = winstate->nfaContext; ctx != NULL; ctx = ctx->next)
+	{
+		if (ctx->states == NULL)
+			continue;
+
+		/*
+		 * Phase 1 already handled frame boundary exceeded contexts by forcing
+		 * mismatch (nfa_match with NULL), which removes all states (all
+		 * states are at VAR positions after advance). So any surviving
+		 * context here must be within its frame boundary.
+		 *
+		 * Compute the (clamped) frame end the same way as Phase 1, using two
+		 * separately checked adds so that "frameOffset + 1" cannot overflow
+		 * when frameOffset is near PG_INT64_MAX.
+		 */
+#ifdef USE_ASSERT_CHECKING
+		if (hasLimitedFrame)
+		{
+			int64		ctxFrameEnd;
+
+			if (pg_add_s64_overflow(ctx->matchStartRow, frameOffset,
+									&ctxFrameEnd) ||
+				pg_add_s64_overflow(ctxFrameEnd, 1, &ctxFrameEnd))
+				ctxFrameEnd = PG_INT64_MAX;
+			Assert(currentPos < ctxFrameEnd);
+		}
+#endif
+
+		nfa_advance(winstate, ctx, currentPos);
+	}
+}
+
+/*
+ * ExecRPRCleanupDeadContexts
+ *
+ * Remove contexts that have failed (no active states and no match).
+ * These are contexts that failed during normal processing and should be
+ * counted as pruned (if length 1) or mismatched (if length > 1).
+ */
+void
+ExecRPRCleanupDeadContexts(WindowAggState *winstate, RPRNFAContext *excludeCtx)
+{
+	RPRNFAContext *ctx;
+	RPRNFAContext *next;
+
+	for (ctx = winstate->nfaContext; ctx != NULL; ctx = next)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		next = ctx->next;
+
+		/* Skip the target context and contexts still processing */
+		if (ctx == excludeCtx || ctx->states != NULL)
+			continue;
+
+		/* Skip successfully matched contexts (will be handled by SKIP logic) */
+		if (ctx->matchEndRow >= ctx->matchStartRow)
+			continue;
+
+		/*
+		 * Failed context: always removed below.  Only record the failure
+		 * statistic if it actually processed its start row; contexts created
+		 * for beyond-partition rows are removed without being counted.
+		 */
+		if (ctx->lastProcessedRow >= ctx->matchStartRow)
+		{
+			int64		failedLen = ctx->lastProcessedRow - ctx->matchStartRow + 1;
+
+			ExecRPRRecordContextFailure(winstate, failedLen);
+		}
+
+		ExecRPRFreeContext(winstate, ctx);
+	}
+}
+
+/*
+ * ExecRPRFinalizeAllContexts
+ *
+ * Partition-end classification policy: kill any VAR states still pursuing
+ * when rows run out, so cleanup sees a uniform ctx->states == NULL across
+ * every context.  By the time this runs, all genuine FIN reaches have
+ * already been recorded in-flight; three shapes survive here:
+ *
+ *   - Pure pursuit (matchedState == NULL): VAR states waiting for input
+ *     that never arrives (e.g., A+ B mid-pattern at partition end).
+ *   - Empty-match candidate + pursuit (matchedState != NULL,
+ *     matchEndRow < matchStartRow): initial-advance FIN-via-skip recorded
+ *     an empty match while VAR states are still chasing a longer one
+ *     (e.g., greedy A*).
+ *   - Real match + pursuit (matchedState != NULL,
+ *     matchEndRow >= matchStartRow): a match has been recorded and VAR
+ *     states are still looping for a longer one.
+ *
+ * Killing the VAR reclassifies the first two as failures in cleanup
+ * (otherwise they linger without contributing to stats).  The third is
+ * stat-neutral -- cleanup skips it either way -- but goes through the
+ * same uniform path so partition-end classification stays centralized.
+ *
+ * Implementation: nfa_match with NULL forces VAR mismatch; nfa_advance
+ * then drains any remaining epsilon transitions.
+ */
+void
+ExecRPRFinalizeAllContexts(WindowAggState *winstate, int64 lastPos)
+{
+	RPRNFAContext *ctx;
+
+	for (ctx = winstate->nfaContext; ctx != NULL; ctx = ctx->next)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		if (ctx->states != NULL)
+		{
+			nfa_match(winstate, ctx, NULL);
+			nfa_advance(winstate, ctx, lastPos);
+		}
+	}
+}
diff --git a/src/backend/executor/meson.build b/src/backend/executor/meson.build
index dc45be0b2ce..0ff4a5b1d83 100644
--- a/src/backend/executor/meson.build
+++ b/src/backend/executor/meson.build
@@ -13,6 +13,7 @@ backend_sources += files(
   'execParallel.c',
   'execPartition.c',
   'execProcnode.c',
+  'execRPR.c',
   'execReplication.c',
   'execSRF.c',
   'execScan.c',
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index f1c524d00df..cb6a484b7de 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -39,12 +39,15 @@
 #include "catalog/pg_proc.h"
 #include "common/int.h"
 #include "executor/executor.h"
+#include "executor/execRPR.h"
 #include "executor/instrument.h"
 #include "executor/nodeWindowAgg.h"
 #include "miscadmin.h"
 #include "nodes/nodeFuncs.h"
+#include "nodes/plannodes.h"
 #include "optimizer/clauses.h"
 #include "optimizer/optimizer.h"
+#include "optimizer/rpr.h"
 #include "parser/parse_agg.h"
 #include "parser/parse_coerce.h"
 #include "utils/acl.h"
@@ -174,6 +177,7 @@ typedef struct WindowStatePerAggData
 	bool		restart;		/* need to restart this agg in this cycle? */
 } WindowStatePerAggData;
 
+
 static void initialize_windowaggregate(WindowAggState *winstate,
 									   WindowStatePerFunc perfuncstate,
 									   WindowStatePerAgg peraggstate);
@@ -210,6 +214,9 @@ static Datum GetAggInitVal(Datum textInitVal, Oid transtype);
 
 static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 					  TupleTableSlot *slot2);
+static int	WinGetSlotInFrame(WindowObject winobj, TupleTableSlot *slot,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout);
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
@@ -228,6 +235,18 @@ static uint8 get_notnull_info(WindowObject winobj,
 							  int64 pos, int argno);
 static void put_notnull_info(WindowObject winobj,
 							 int64 pos, int argno, bool isnull);
+static bool rpr_is_defined(WindowAggState *winstate);
+static int64 row_is_in_reduced_frame(WindowObject winobj, int64 pos);
+
+static void clear_reduced_frame(WindowAggState *winstate);
+static int	get_reduced_frame_status(WindowAggState *winstate, int64 pos);
+static void update_reduced_frame(WindowObject winobj, int64 pos);
+
+/* Forward declarations - NFA row evaluation */
+static bool nfa_evaluate_row(WindowObject winobj, int64 pos, bool *varMatched);
+
+/* Forward declarations - navigation offset evaluation */
+static void eval_define_offsets(WindowAggState *winstate, List *defineClause);
 
 /*
  * Not null info bit array consists of 2-bit items
@@ -821,6 +840,9 @@ eval_windowaggregates(WindowAggState *winstate)
 	 *	   transition function, or
 	 *	 - we have an EXCLUSION clause, or
 	 *	 - if the new frame doesn't overlap the old one
+	 *   - if RPR (Row Pattern Recognition) is enabled, because the reduced
+	 *     frame depends on pattern matching results which can differ entirely
+	 *     from row to row, making inverse transition optimization inapplicable
 	 *
 	 * Note that we don't strictly need to restart in the last case, but if
 	 * we're going to remove all rows from the aggregation anyway, a restart
@@ -835,7 +857,8 @@ eval_windowaggregates(WindowAggState *winstate)
 			(winstate->aggregatedbase != winstate->frameheadpos &&
 			 !OidIsValid(peraggstate->invtransfn_oid)) ||
 			(winstate->frameOptions & FRAMEOPTION_EXCLUSION) ||
-			winstate->aggregatedupto <= winstate->frameheadpos)
+			winstate->aggregatedupto <= winstate->frameheadpos ||
+			rpr_is_defined(winstate))
 		{
 			peraggstate->restart = true;
 			numaggs_restart++;
@@ -964,6 +987,14 @@ eval_windowaggregates(WindowAggState *winstate)
 	{
 		winstate->aggregatedupto = winstate->frameheadpos;
 		ExecClearTuple(agg_row_slot);
+
+		/*
+		 * If RPR is defined, we do not use aggregatedupto_nonrestarted.  To
+		 * avoid assertion failure below, we reset aggregatedupto_nonrestarted
+		 * to frameheadpos.
+		 */
+		if (rpr_is_defined(winstate))
+			aggregatedupto_nonrestarted = winstate->frameheadpos;
 	}
 
 	/*
@@ -975,7 +1006,7 @@ eval_windowaggregates(WindowAggState *winstate)
 	 */
 	for (;;)
 	{
-		int			ret;
+		int64		ret;
 
 		/* Fetch next row if we didn't already */
 		if (TupIsNull(agg_row_slot))
@@ -993,9 +1024,40 @@ eval_windowaggregates(WindowAggState *winstate)
 							  agg_row_slot, false);
 		if (ret < 0)
 			break;
+
 		if (ret == 0)
 			goto next_tuple;
 
+		if (rpr_is_defined(winstate))
+		{
+			/*
+			 * If currentpos is already decided but aggregatedupto is not yet
+			 * determined, we've passed the last reduced frame.
+			 */
+			if (get_reduced_frame_status(winstate, winstate->currentpos)
+				!= RF_NOT_DETERMINED &&
+				get_reduced_frame_status(winstate, winstate->aggregatedupto)
+				== RF_NOT_DETERMINED)
+				break;
+
+			/*
+			 * Calculate the reduced frame for aggregatedupto.
+			 */
+			ret = row_is_in_reduced_frame(winstate->agg_winobj,
+										  winstate->aggregatedupto);
+			if (ret == -1)		/* unmatched row */
+				break;
+
+			/*
+			 * Check if current row is inside a match but not the head
+			 * (skipped), and it's the base row for aggregation.
+			 */
+			if (get_reduced_frame_status(winstate,
+										 winstate->aggregatedupto) == RF_SKIPPED &&
+				winstate->aggregatedupto == winstate->aggregatedbase)
+				break;
+		}
+
 		/* Set tuple context for evaluation of aggregate arguments */
 		winstate->tmpcontext->ecxt_outertuple = agg_row_slot;
 
@@ -1024,6 +1086,7 @@ next_tuple:
 		ExecClearTuple(agg_row_slot);
 	}
 
+
 	/* The frame's end is not supposed to move backwards, ever */
 	Assert(aggregatedupto_nonrestarted <= winstate->aggregatedupto);
 
@@ -1191,6 +1254,28 @@ prepare_tuplestore(WindowAggState *winstate)
 		}
 	}
 
+	/* Create read/mark pointers for RPR navigation if needed */
+	if (winstate->nav_winobj)
+	{
+		/*
+		 * Allocate mark and read pointers for RPR navigation.
+		 *
+		 * If navMaxOffsetKind == RPR_NAV_OFFSET_FIXED, we advance the mark
+		 * based on (currentpos - navMaxOffset) and optionally
+		 * (nfaContext->matchStartRow + navFirstOffset), allowing
+		 * tuplestore_trim() to free rows that are no longer reachable.
+		 *
+		 * RPR_NAV_OFFSET_NEEDS_EVAL is resolved at executor init; by this
+		 * point it is either FIXED or RETAIN_ALL.
+		 */
+		winstate->nav_winobj->markptr =
+			tuplestore_alloc_read_pointer(winstate->buffer, 0);
+		winstate->nav_winobj->readptr =
+			tuplestore_alloc_read_pointer(winstate->buffer,
+										  EXEC_FLAG_BACKWARD);
+		winstate->nav_winobj->markpos = 0;
+	}
+
 	/*
 	 * If we are in RANGE or GROUPS mode, then determining frame boundaries
 	 * requires physical access to the frame endpoint rows, except in certain
@@ -1247,6 +1332,8 @@ begin_partition(WindowAggState *winstate)
 	winstate->framehead_valid = false;
 	winstate->frametail_valid = false;
 	winstate->grouptail_valid = false;
+	if (rpr_is_defined(winstate))
+		clear_reduced_frame(winstate);
 	winstate->spooled_rows = 0;
 	winstate->currentpos = 0;
 	winstate->frameheadpos = 0;
@@ -1300,6 +1387,13 @@ begin_partition(WindowAggState *winstate)
 		winstate->aggregatedupto = 0;
 	}
 
+	/* reset mark and seek positions for RPR navigation */
+	if (winstate->nav_winobj)
+	{
+		winstate->nav_winobj->markpos = -1;
+		winstate->nav_winobj->seekpos = -1;
+	}
+
 	/* reset mark and seek positions for each real window function */
 	for (int i = 0; i < numfuncs; i++)
 	{
@@ -1468,6 +1562,21 @@ release_partition(WindowAggState *winstate)
 		tuplestore_clear(winstate->buffer);
 	winstate->partition_spooled = false;
 	winstate->next_partition = true;
+
+	/* Reset RPR match results */
+	clear_reduced_frame(winstate);
+
+	/* Reset NFA state for new partition */
+	winstate->nfaContext = NULL;
+	winstate->nfaContextTail = NULL;
+	winstate->nfaContextFree = NULL;
+	winstate->nfaStateFree = NULL;
+	winstate->nfaLastProcessedRow = -1;
+	winstate->nfaStatesActive = 0;
+	winstate->nfaContextsActive = 0;
+
+	/* Invalidate the nav slot position cache for the new partition. */
+	winstate->nav_slot_pos = -1;
 }
 
 /*
@@ -2263,6 +2372,16 @@ calculate_frame_offsets(PlanState *pstate)
 				ereport(ERROR,
 						(errcode(ERRCODE_INVALID_PRECEDING_OR_FOLLOWING_SIZE),
 						 errmsg("frame ending offset must not be negative")));
+
+			/*
+			 * Row pattern recognition forbids a zero-length frame end;
+			 * checked here so a non-constant offset (e.g. a bind parameter)
+			 * is caught, not just a literal 0.
+			 */
+			if (winstate->rpPattern != NULL && offset == 0)
+				ereport(ERROR,
+						errcode(ERRCODE_WINDOWING_ERROR),
+						errmsg("frame ending offset must be positive with row pattern recognition"));
 		}
 	}
 	winstate->all_first = false;
@@ -2396,6 +2515,16 @@ ExecWindowAgg(PlanState *pstate)
 		/* don't evaluate the window functions when we're in pass-through mode */
 		if (winstate->status == WINDOWAGG_RUN)
 		{
+			/*
+			 * If RPR is defined and skip mode is next row, clear the current
+			 * match so the next row triggers re-evaluation.
+			 */
+			if (rpr_is_defined(winstate))
+			{
+				if (winstate->rpSkipTo == ST_NEXT_ROW)
+					clear_reduced_frame(winstate);
+			}
+
 			/*
 			 * Evaluate true window functions
 			 */
@@ -2435,6 +2564,43 @@ ExecWindowAgg(PlanState *pstate)
 		if (winstate->grouptail_ptr >= 0)
 			update_grouptailpos(winstate);
 
+		/*
+		 * Advance RPR navigation mark pointer if possible, so that
+		 * tuplestore_trim() can free rows no longer reachable by navigation.
+		 */
+		if (winstate->nav_winobj &&
+			winstate->rpPattern != NULL &&
+			winstate->navMaxOffsetKind == RPR_NAV_OFFSET_FIXED)
+		{
+			int64		navmarkpos;
+
+			/* Backward reach from PREV/LAST/compound PREV_LAST/NEXT_LAST */
+			if (winstate->currentpos > winstate->navMaxOffset)
+				navmarkpos = winstate->currentpos - winstate->navMaxOffset;
+			else
+				navmarkpos = 0;
+
+			/*
+			 * If FIRST is used, also consider match_start + navFirstOffset.
+			 * The oldest active context (nfaContext) has the smallest
+			 * matchStartRow.
+			 */
+			if (winstate->hasFirstNav &&
+				winstate->navFirstOffsetKind == RPR_NAV_OFFSET_FIXED &&
+				winstate->nfaContext != NULL)
+			{
+				int64		firstreach;
+
+				if (!pg_add_s64_overflow(winstate->nfaContext->matchStartRow,
+										 winstate->navFirstOffset,
+										 &firstreach))
+					navmarkpos = Min(navmarkpos, Max(firstreach, 0));
+			}
+
+			if (navmarkpos > winstate->nav_winobj->markpos)
+				WinSetMarkPosition(winstate->nav_winobj, navmarkpos);
+		}
+
 		/*
 		 * Truncate any no-longer-needed rows from the tuplestore.
 		 */
@@ -2660,6 +2826,20 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 	winstate->temp_slot_2 = ExecInitExtraTupleSlot(estate, scanDesc,
 												   &TTSOpsMinimalTuple);
 
+	if (node->rpPattern != NULL)
+	{
+		winstate->nav_slot = ExecInitExtraTupleSlot(estate, scanDesc,
+													&TTSOpsMinimalTuple);
+		winstate->nav_slot_pos = -1;
+
+		winstate->nav_null_slot = ExecInitExtraTupleSlot(estate, scanDesc,
+														 &TTSOpsMinimalTuple);
+		winstate->nav_null_slot = ExecStoreAllNullTuple(winstate->nav_null_slot);
+
+		winstate->nav_saved_outertuple = NULL;
+		winstate->nav_match_start = 0;
+	}
+
 	/*
 	 * create frame head and tail slots only if needed (must create slots in
 	 * exactly the same cases that update_frameheadpos and update_frametailpos
@@ -2828,6 +3008,23 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 		winstate->agg_winobj = agg_winobj;
 	}
 
+	/*
+	 * Set up WindowObject for RPR navigation opcodes.  This is separate from
+	 * agg_winobj because it needs its own read pointer to avoid interfering
+	 * with aggregate processing.
+	 */
+	if (node->rpPattern != NULL)
+	{
+		WindowObject nav_winobj = makeNode(WindowObjectData);
+
+		nav_winobj->winstate = winstate;
+		nav_winobj->argstates = NIL;
+		nav_winobj->localmem = NULL;
+		nav_winobj->markptr = -1;
+		nav_winobj->readptr = -1;
+		winstate->nav_winobj = nav_winobj;
+	}
+
 	/* Set the status to running */
 	winstate->status = WINDOWAGG_RUN;
 
@@ -2846,6 +3043,81 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 	winstate->inRangeAsc = node->inRangeAsc;
 	winstate->inRangeNullsFirst = node->inRangeNullsFirst;
 
+	/* Set up SKIP TO type */
+	winstate->rpSkipTo = node->rpSkipTo;
+	/* Set up row pattern recognition PATTERN clause (compiled NFA) */
+	winstate->rpPattern = node->rpPattern;
+	/* Set up nav offsets for tuplestore trim; resolve any NEEDS_EVAL kinds */
+	winstate->navMaxOffsetKind = node->navMaxOffsetKind;
+	winstate->navMaxOffset = node->navMaxOffset;
+	winstate->hasFirstNav = node->hasFirstNav;
+	winstate->navFirstOffsetKind = node->navFirstOffsetKind;
+	winstate->navFirstOffset = node->navFirstOffset;
+	eval_define_offsets(winstate, node->defineClause);
+
+	/* Copy match_start dependency bitmapset for per-context evaluation */
+	winstate->defineMatchStartDependent = bms_copy(node->defineMatchStartDependent);
+
+	/* Calculate NFA state size and allocate cycle detection bitmap */
+	if (node->rpPattern != NULL)
+	{
+		int			nfaVisitedNWords;
+
+		winstate->nfaStateSize = offsetof(RPRNFAState, counts) +
+			sizeof(int32) * node->rpPattern->maxDepth;
+		nfaVisitedNWords =
+			(node->rpPattern->numElements - 1) / BITS_PER_BITMAPWORD + 1;
+		winstate->nfaVisitedElems = palloc0(sizeof(bitmapword) *
+											nfaVisitedNWords);
+		/* High-water mark sentinels: no bits set yet. */
+		winstate->nfaVisitedMinWord = PG_INT16_MAX;
+		winstate->nfaVisitedMaxWord = -1;
+	}
+
+	/* Set up row pattern recognition DEFINE clause */
+	winstate->defineVariableList = NIL;
+	winstate->defineClauseList = NIL;
+	if (node->defineClause != NIL)
+	{
+		/*
+		 * Compile DEFINE clause expressions.  PREV/NEXT navigation is handled
+		 * by EEOP_RPR_NAV_SET/RESTORE opcodes emitted during ExecInitExpr, so
+		 * no varno rewriting is needed here.
+		 */
+		foreach_node(TargetEntry, te, node->defineClause)
+		{
+			char	   *name = te->resname;
+			Expr	   *expr = te->expr;
+			ExprState  *exps;
+
+			winstate->defineVariableList =
+				lappend(winstate->defineVariableList,
+						makeString(pstrdup(name)));
+			exps = ExecInitExpr(expr, (PlanState *) winstate);
+			winstate->defineClauseList =
+				lappend(winstate->defineClauseList, exps);
+		}
+	}
+
+	/* Initialize NFA free lists for row pattern matching */
+	winstate->nfaContext = NULL;
+	winstate->nfaContextTail = NULL;
+	winstate->nfaContextFree = NULL;
+	winstate->nfaStateFree = NULL;
+	winstate->nfaLastProcessedRow = -1;
+	winstate->nfaStatesActive = 0;
+	winstate->nfaContextsActive = 0;
+
+	/*
+	 * Allocate varMatched array for NFA evaluation. With the new varNames
+	 * ordering (DEFINE order first), varId == defineIdx for all defined
+	 * variables, so no mapping is needed.
+	 */
+	if (list_length(winstate->defineVariableList) > 0)
+		winstate->nfaVarMatched = palloc0(sizeof(bool) *
+										  list_length(winstate->defineVariableList));
+	else
+		winstate->nfaVarMatched = NULL;
 	winstate->all_first = true;
 	winstate->partition_spooled = false;
 	winstate->more_partitions = false;
@@ -2854,6 +3126,42 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 	return winstate;
 }
 
+/*
+ * ExecRPRNavGetSlot
+ *
+ * Fetch tuple at given position for RPR navigation opcodes.
+ * Returns nav_slot with the tuple loaded, or nav_null_slot if out of range.
+ */
+TupleTableSlot *
+ExecRPRNavGetSlot(WindowAggState *winstate, int64 pos)
+{
+	WindowObject winobj = winstate->nav_winobj;
+	TupleTableSlot *slot = winstate->nav_slot;
+
+	if (pos < 0)
+		return winstate->nav_null_slot;
+
+	/*
+	 * If nav_slot already holds this position, return it without re-fetching.
+	 * This is critical when multiple PREV/NEXT calls in the same expression
+	 * navigate to the same row, because re-fetching would free the slot's
+	 * tuple memory and invalidate any pass-by-ref Datum pointers from earlier
+	 * navigation results.
+	 */
+	if (winstate->nav_slot_pos == pos)
+		return slot;
+
+	if (!window_gettupleslot(winobj, pos, slot))
+	{
+		winstate->nav_slot_pos = -1;
+		return winstate->nav_null_slot;
+	}
+
+	winstate->nav_slot_pos = pos;
+	return slot;
+}
+
+
 /* -----------------
  * ExecEndWindowAgg
  * -----------------
@@ -2911,6 +3219,8 @@ ExecReScanWindowAgg(WindowAggState *node)
 	ExecClearTuple(node->agg_row_slot);
 	ExecClearTuple(node->temp_slot_1);
 	ExecClearTuple(node->temp_slot_2);
+	if (node->nav_slot)
+		ExecClearTuple(node->nav_slot);
 	if (node->framehead_slot)
 		ExecClearTuple(node->framehead_slot);
 	if (node->frametail_slot)
@@ -3271,7 +3581,8 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 		return false;
 
 	if (pos < winobj->markpos)
-		elog(ERROR, "cannot fetch row before WindowObject's mark position");
+		elog(ERROR, "cannot fetch row: " INT64_FORMAT " before WindowObject's mark position: " INT64_FORMAT,
+			 pos, winobj->markpos);
 
 	oldcontext = MemoryContextSwitchTo(winstate->ss.ps.ps_ExprContext->ecxt_per_query_memory);
 
@@ -3389,6 +3700,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 	int			notnull_offset;
 	int			notnull_relpos;
 	int			forward;
+	int64		num_reduced_frame;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
@@ -3417,6 +3729,13 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 			/* rejecting relpos > 0 is easy and simplifies code below */
 			if (relpos > 0)
 				goto out_of_frame;
+
+			/*
+			 * RPR cares about frame head pos. Need to call
+			 * update_frameheadpos
+			 */
+			update_frameheadpos(winstate);
+
 			update_frametailpos(winstate);
 			abs_pos = winstate->frametailpos - 1;
 			mark_pos = 0;		/* keep compiler quiet */
@@ -3432,6 +3751,35 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 	 * Get the next nonnull value in the frame, moving forward or backward
 	 * until we find a value or reach the frame's end.
 	 */
+
+	/*
+	 * Check whether current row is in reduced frame.
+	 */
+	num_reduced_frame = row_is_in_reduced_frame(winobj, winstate->frameheadpos);
+	if (num_reduced_frame < 0)	/* unmatched or skipped row */
+		goto out_of_frame;
+	else if (num_reduced_frame > 0) /* the first row of the reduced frame */
+	{
+		/*
+		 * Early check if row could be out of reduced frame.  When RPR is
+		 * enabled, EXCLUDE clause cannot be specified and the frame is always
+		 * contiguous.  So we can safely perform the following checks. Note,
+		 * however, it is possible that a row is out of reduced frame if
+		 * there's a NULL in the middle. So we need to check it in the
+		 * following do loop.
+		 */
+		if (seektype == WINDOW_SEEK_HEAD && relpos >= num_reduced_frame)
+			goto out_of_frame;
+		if (seektype == WINDOW_SEEK_TAIL)
+		{
+			if (notnull_relpos >= num_reduced_frame)
+				goto out_of_frame;
+
+			/* not out of reduced frame. Set abspos as a starting point */
+			abs_pos = winstate->frameheadpos + num_reduced_frame - 1;
+		}
+	}
+
 	do
 	{
 		int			inframe;
@@ -3493,6 +3841,16 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 		}
 advance:
 		abs_pos += forward;
+		if (rpr_is_defined(winstate))
+		{
+			/*
+			 * Check whether we are still in the reduced frame.  (also check
+			 * if we succeeded in getting the target row).
+			 */
+			num_reduced_frame--;
+			if (num_reduced_frame <= 0 && notnull_offset <= notnull_relpos)
+				goto out_of_frame;
+		}
 	} while (notnull_offset <= notnull_relpos);
 
 	if (set_mark)
@@ -3635,87 +3993,940 @@ put_notnull_info(WindowObject winobj, int64 pos, int argno, bool isnull)
 	mbp[bpos] = mb;
 }
 
-/***********************************************************************
- * API exposed to window functions
- ***********************************************************************/
+/*
+ * eval_nav_offset_helper
+ *		Evaluate an offset expression at executor init time for trim
+ *		optimization.  Returns the offset value, or 0 for NULL/negative
+ *		(these will cause a runtime error during actual navigation, so the
+ *		trim value is irrelevant).
+ */
+static int64
+eval_nav_offset_helper(WindowAggState *winstate, Expr *offset_expr,
+					   int64 defaultOffset)
+{
+	ExprContext *econtext = winstate->ss.ps.ps_ExprContext;
+	ExprState  *estate;
+	Datum		val;
+	bool		isnull;
+	int64		offset;
+
+	if (offset_expr == NULL)
+		return defaultOffset;
+
+	estate = ExecInitExpr(offset_expr, (PlanState *) winstate);
+	val = ExecEvalExprSwitchContext(estate, econtext, &isnull);
 
+	if (isnull)
+		return 0;
+
+	offset = DatumGetInt64(val);
+	if (offset < 0)
+		return 0;
+
+	return offset;
+}
+
+typedef struct
+{
+	WindowAggState *winstate;
+	int64		maxOffset;		/* max backward-reach offset across all nav
+								 * exprs */
+	bool		maxOverflow;	/* true if backward-reach overflow detected */
+	int64		minFirstOffset; /* min forward-from-match_start offset; may be
+								 * negative (PREV_FIRST: inner - outer < 0) */
+} EvalDefineOffsetsContext;
 
 /*
- * WinCheckAndInitializeNullTreatment
- *		Check null treatment clause and sets ignore_nulls
+ * visit_nav_exec
+ *		nav_traversal_walker callback (NavVisitFn) for the executor side.
+ *		At each RPRNavExpr, evaluates the nav's offset expression(s) at
+ *		runtime via eval_nav_offset_helper and accumulates:
  *
- * Window functions should call this to check if they are being called with
- * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ *		  - maxOffset (backward reach): PREV, LAST-with-offset, compound
+ *			PREV_LAST (sets maxOverflow on int64 overflow), compound
+ *			NEXT_LAST (= max(inner - outer, 0))
+ *		  - minFirstOffset (forward reach from match_start): FIRST,
+ *			compound PREV_FIRST (= inner - outer, may be negative),
+ *			compound NEXT_FIRST (= inner + outer, clamped to PG_INT64_MAX on
+ *			overflow; always >= 0 so never updates minFirstOffset in practice)
+ *
+ * Counterpart of visit_nav_plan but using runtime evaluation instead of
+ * Const folding; runs only for offsets the planner marked NEEDS_EVAL.
+ * Match-start dependency is not recomputed here -- the planner's bitmapset
+ * is reused via winstate->defineMatchStartDependent.
  */
-void
-WinCheckAndInitializeNullTreatment(WindowObject winobj,
-								   bool allowNullTreatment,
-								   FunctionCallInfo fcinfo)
+static void
+visit_nav_exec(NavTraversal *t, RPRNavExpr *nav)
 {
-	Assert(WindowObjectIsValid(winobj));
-	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	EvalDefineOffsetsContext *context = (EvalDefineOffsetsContext *) t->data;
+
+	/*
+	 * Parser guarantee (mirrors visit_nav_plan): nav's direct children are
+	 * never RPRNavExpr -- compound nesting is flattened in place and any
+	 * other nesting is rejected.  Outer-kind dispatch is sufficient.
+	 */
+	Assert(nav->arg == NULL || !IsA(nav->arg, RPRNavExpr));
+	Assert(nav->offset_arg == NULL || !IsA(nav->offset_arg, RPRNavExpr));
+	Assert(nav->compound_offset_arg == NULL ||
+		   !IsA(nav->compound_offset_arg, RPRNavExpr));
+
+	/* Backward reach: PREV, LAST-with-offset */
+	if (!context->maxOverflow)
 	{
-		const char *funcname = get_func_name(fcinfo->flinfo->fn_oid);
+		int64		reach = 0;
+		bool		gotReach = false;
 
-		if (!funcname)
-			elog(ERROR, "could not get function name");
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("function %s does not allow RESPECT/IGNORE NULLS",
-						funcname)));
+		if (nav->kind == RPR_NAV_PREV)
+		{
+			reach = eval_nav_offset_helper(context->winstate,
+										   nav->offset_arg, 1);
+			gotReach = true;
+		}
+		else if (nav->kind == RPR_NAV_LAST && nav->offset_arg != NULL)
+		{
+			reach = eval_nav_offset_helper(context->winstate,
+										   nav->offset_arg, 0);
+			gotReach = true;
+		}
+		else if (nav->kind == RPR_NAV_PREV_LAST ||
+				 nav->kind == RPR_NAV_NEXT_LAST)
+		{
+			int64		inner = eval_nav_offset_helper(context->winstate,
+													   nav->offset_arg, 0);
+			int64		outer = eval_nav_offset_helper(context->winstate,
+													   nav->compound_offset_arg, 1);
+
+			if (nav->kind == RPR_NAV_PREV_LAST)
+			{
+				if (pg_add_s64_overflow(inner, outer, &reach))
+					context->maxOverflow = true;
+				else
+					gotReach = true;
+			}
+			else
+			{
+				reach = Max(inner - outer, 0);
+				gotReach = true;
+			}
+		}
+
+		if (gotReach)
+			context->maxOffset = Max(context->maxOffset, reach);
+	}
+
+	/* Forward reach from match_start: FIRST, compound PREV_FIRST/NEXT_FIRST */
+	if (nav->kind == RPR_NAV_FIRST)
+	{
+		int64		reach;
+
+		reach = eval_nav_offset_helper(context->winstate,
+									   nav->offset_arg, 0);
+		context->minFirstOffset = Min(context->minFirstOffset, reach);
+	}
+	else if (nav->kind == RPR_NAV_PREV_FIRST ||
+			 nav->kind == RPR_NAV_NEXT_FIRST)
+	{
+		int64		inner = eval_nav_offset_helper(context->winstate,
+												   nav->offset_arg, 0);
+		int64		outer = eval_nav_offset_helper(context->winstate,
+												   nav->compound_offset_arg, 1);
+		int64		reach;
+
+		if (nav->kind == RPR_NAV_PREV_FIRST)
+		{
+			/*
+			 * reach = inner - outer.  Both are non-negative, so the result >=
+			 * -PG_INT64_MAX, which cannot underflow int64.
+			 */
+			reach = inner - outer;
+		}
+		else
+		{
+			/*
+			 * NEXT_FIRST: reach = inner + outer.  This can overflow, but the
+			 * result is always >= 0, so it never updates minFirstOffset
+			 * (which tracks the minimum).  Clamp to PG_INT64_MAX on overflow.
+			 */
+			if (pg_add_s64_overflow(inner, outer, &reach))
+				reach = PG_INT64_MAX;
+		}
+		context->minFirstOffset = Min(context->minFirstOffset, reach);
 	}
-	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
-		winobj->ignore_nulls = IGNORE_NULLS;
 }
 
 /*
- * WinGetPartitionLocalMemory
- *		Get working memory that lives till end of partition processing
+ * eval_define_offsets
+ *		Evaluate non-constant nav offsets at executor init time.
  *
- * On first call within a given partition, this allocates and zeroes the
- * requested amount of space.  Subsequent calls just return the same chunk.
+ * Called when the planner set navMaxOffsetKind and/or navFirstOffsetKind
+ * to RPR_NAV_OFFSET_NEEDS_EVAL because some offset contains a parameter
+ * or non-foldable expression.  Updates only the fields whose kind was
+ * NEEDS_EVAL; FIXED kinds are left unchanged.
  *
- * Memory obtained this way is normally used to hold state that should be
- * automatically reset for each new partition.  If a window function wants
- * to hold state across the whole query, fcinfo->fn_extra can be used in the
- * usual way for that.
+ * On backward-reach overflow, sets navMaxOffsetKind to
+ * RPR_NAV_OFFSET_RETAIN_ALL so that tuplestore trim is disabled for
+ * backward navigation.
  */
-void *
-WinGetPartitionLocalMemory(WindowObject winobj, Size sz)
+static void
+eval_define_offsets(WindowAggState *winstate, List *defineClause)
 {
-	Assert(WindowObjectIsValid(winobj));
-	if (winobj->localmem == NULL)
-		winobj->localmem =
-			MemoryContextAllocZero(winobj->winstate->partcontext, sz);
-	return winobj->localmem;
+	EvalDefineOffsetsContext ctx;
+	NavTraversal trav;
+	bool		needsMax = (winstate->navMaxOffsetKind == RPR_NAV_OFFSET_NEEDS_EVAL);
+	bool		needsFirst = (winstate->hasFirstNav &&
+							  winstate->navFirstOffsetKind == RPR_NAV_OFFSET_NEEDS_EVAL);
+
+	if (!needsMax && !needsFirst)
+		return;
+
+	ctx.winstate = winstate;
+	ctx.maxOffset = 0;
+	ctx.maxOverflow = false;
+	ctx.minFirstOffset = PG_INT64_MAX;
+
+	trav.visit = visit_nav_exec;
+	trav.data = &ctx;
+
+	foreach_node(TargetEntry, te, defineClause)
+	{
+		nav_traversal_walker((Node *) te->expr, &trav);
+	}
+
+	if (needsMax)
+	{
+		if (ctx.maxOverflow)
+		{
+			winstate->navMaxOffsetKind = RPR_NAV_OFFSET_RETAIN_ALL;
+			winstate->navMaxOffset = 0;
+		}
+		else
+		{
+			winstate->navMaxOffsetKind = RPR_NAV_OFFSET_FIXED;
+			winstate->navMaxOffset = ctx.maxOffset;
+		}
+	}
+
+	if (needsFirst)
+	{
+		winstate->navFirstOffsetKind = RPR_NAV_OFFSET_FIXED;
+		if (ctx.minFirstOffset < PG_INT64_MAX)
+			winstate->navFirstOffset = ctx.minFirstOffset;
+		else
+			winstate->navFirstOffset = PG_INT64_MAX;
+	}
 }
 
 /*
- * WinGetCurrentPosition
- *		Return the current row's position (counting from 0) within the current
- *		partition.
+ * rpr_is_defined
+ * Return true if row pattern recognition is defined.
  */
-int64
-WinGetCurrentPosition(WindowObject winobj)
+static bool
+rpr_is_defined(WindowAggState *winstate)
 {
-	Assert(WindowObjectIsValid(winobj));
-	return winobj->winstate->currentpos;
+	return winstate->rpPattern != NULL;
 }
 
 /*
- * WinGetPartitionRowCount
- *		Return total number of rows contained in the current partition.
+ * -----------------
+ * row_is_in_reduced_frame
+ * Determine whether a row is in the current row's reduced window frame
+ * according to row pattern matching
  *
- * Note: this is a relatively expensive operation because it forces the
- * whole partition to be "spooled" into the tuplestore at once.  Once
- * executed, however, additional calls within the same partition are cheap.
+ * The row must have already been determined to be in a full window frame
+ * and fetched into the slot.
+ *
+ * Returns:
+ * = 0, RPR is not defined.
+ * >0, if the row is the first in the reduced frame. Return the number of rows
+ * in the reduced frame.
+ * -1, if the row is an unmatched row
+ * -2, if the row is in the reduced frame but needed to be skipped because of
+ * AFTER MATCH SKIP PAST LAST ROW
+ * -----------------
  */
-int64
-WinGetPartitionRowCount(WindowObject winobj)
+static int64
+row_is_in_reduced_frame(WindowObject winobj, int64 pos)
 {
-	Assert(WindowObjectIsValid(winobj));
-	spool_tuples(winobj->winstate, -1);
-	return winobj->winstate->spooled_rows;
+	WindowAggState *winstate = winobj->winstate;
+	int			state;
+	int64		rtn;
+
+	if (!rpr_is_defined(winstate))
+	{
+		/*
+		 * RPR is not defined. Assume that we are always in the reduced window
+		 * frame.
+		 */
+		rtn = 0;
+		return rtn;
+	}
+
+	state = get_reduced_frame_status(winstate, pos);
+
+	if (state == RF_NOT_DETERMINED)
+	{
+		update_frameheadpos(winstate);
+		update_reduced_frame(winobj, pos);
+	}
+
+	state = get_reduced_frame_status(winstate, pos);
+
+	switch (state)
+	{
+		case RF_FRAME_HEAD:
+			rtn = winstate->rpr_match_length;
+			break;
+
+		case RF_SKIPPED:
+			rtn = -2;
+			break;
+
+		case RF_UNMATCHED:
+		case RF_EMPTY_MATCH:
+			rtn = -1;
+			break;
+
+		default:
+			elog(ERROR, "unrecognized state: %d at: " INT64_FORMAT,
+				 state, pos);
+			break;
+	}
+
+	return rtn;
+}
+
+/*
+ * clear_reduced_frame
+ * Clear reduced frame status
+ */
+static void
+clear_reduced_frame(WindowAggState *winstate)
+{
+	winstate->rpr_match_valid = false;
+	winstate->rpr_match_matched = false;
+	winstate->rpr_match_start = -1;
+	winstate->rpr_match_length = 0;
+}
+
+/*
+ * get_reduced_frame_status
+ *		Look up a position against the current match.
+ *
+ * Returns one of the RF_* constants:
+ *   RF_NOT_DETERMINED  pos has not been processed yet
+ *   RF_FRAME_HEAD      pos is the start of the current match
+ *   RF_SKIPPED         pos is inside the current match but not the start
+ *   RF_UNMATCHED       pos is processed but not part of any match
+ *   RF_EMPTY_MATCH     pos is the start of an empty (zero-length) match
+ *
+ * update_reduced_frame() records the current match as exactly one of three
+ * (rpr_match_matched, rpr_match_length) shapes: (false, 1) for unmatched,
+ * (true, 0) for an empty match, and (true, >= 1) for a real match.  The
+ * tests below form a cascade with early returns: each is a minimal check
+ * that relies on the negations the preceding returns have already
+ * established, so their order is significant.  The "by here" notes spell
+ * out the running invariant; reordering a test would misclassify one of
+ * the three shapes.
+ */
+static int
+get_reduced_frame_status(WindowAggState *winstate, int64 pos)
+{
+	int64		start = winstate->rpr_match_start;
+	int64		length = winstate->rpr_match_length;
+
+	if (!winstate->rpr_match_valid)
+		return RF_NOT_DETERMINED;
+
+	/*
+	 * By here the record is valid and holds one of the three shapes above.
+	 *
+	 * The empty match (true, 0) must be classified first: it has length 0, so
+	 * the range test below would compute start + length == start and reject
+	 * its own start position as out of range.
+	 */
+	if (pos == start && winstate->rpr_match_matched && length == 0)
+		return RF_EMPTY_MATCH;
+
+	/*
+	 * By here length >= 1 -- the only zero-length record, the empty match,
+	 * has been handled -- so [start, start + length) is a well-formed range.
+	 */
+	if (pos < start || pos >= start + length)
+		return RF_NOT_DETERMINED;
+
+	/*
+	 * By here pos lies within [start, start + length).  An unmatched record
+	 * is (false, 1), so this returns for its single in-range position.
+	 */
+	if (!winstate->rpr_match_matched)
+		return RF_UNMATCHED;
+
+	/* By here the match is real (true, >= 1) and pos is one of its rows. */
+	if (pos == start)
+		return RF_FRAME_HEAD;
+
+	return RF_SKIPPED;
+}
+
+/*
+ * update_reduced_frame
+ *		Update reduced frame info using multi-context NFA pattern matching.
+ *
+ * Maintains multiple NFA contexts simultaneously, one for each potential
+ * match start position. This allows sharing row evaluations across contexts,
+ * avoiding redundant DEFINE clause evaluations when rewinding for SKIP TO
+ * NEXT ROW mode.
+ *
+ * Key optimizations:
+ * - Row evaluations (expensive DEFINE clauses) happen only once per row
+ * - All active contexts share the same evaluation results
+ * - Contexts persist across calls, enabling O(n) DEFINE evaluations
+ */
+static void
+update_reduced_frame(WindowObject winobj, int64 pos)
+{
+	WindowAggState *winstate = winobj->winstate;
+	RPRNFAContext *targetCtx;
+	int64		currentPos;
+	int64		startPos;
+	int			frameOptions = winstate->frameOptions;
+	bool		hasLimitedFrame;
+	int64		frameOffset = 0;
+	int64		matchLen;
+
+	/*
+	 * Check if we have a limited frame (ROWS ... N FOLLOWING). Each context
+	 * needs its own frame end based on matchStartRow + offset.
+	 */
+	hasLimitedFrame = (frameOptions & FRAMEOPTION_ROWS) &&
+		!(frameOptions & FRAMEOPTION_END_UNBOUNDED_FOLLOWING);
+	if (hasLimitedFrame)
+		frameOffset = DatumGetInt64(winstate->endOffsetValue);
+
+	/*
+	 * Case 1: pos is before any existing context's start position. This means
+	 * the position was already processed and determined unmatched. Head is
+	 * the oldest context (lowest matchStartRow) since contexts are added at
+	 * tail with increasing positions.
+	 */
+	if (winstate->nfaContext != NULL &&
+		pos < winstate->nfaContext->matchStartRow)
+	{
+		/* already processed, unmatched */
+		winstate->rpr_match_valid = true;
+		winstate->rpr_match_matched = false;
+		winstate->rpr_match_start = pos;
+		winstate->rpr_match_length = 1;
+		return;
+	}
+
+	/*
+	 * Case 2: Find existing context for this pos, or create new one.
+	 */
+	targetCtx = ExecRPRGetHeadContext(winstate, pos);
+	if (targetCtx == NULL)
+	{
+		/*
+		 * No context exists. If pos is already processed, it means this row
+		 * was already determined to be unmatched or skipped - no need to
+		 * reprocess.
+		 */
+		if (pos <= winstate->nfaLastProcessedRow)
+		{
+			/* already processed, unmatched */
+			winstate->rpr_match_valid = true;
+			winstate->rpr_match_matched = false;
+			winstate->rpr_match_start = pos;
+			winstate->rpr_match_length = 1;
+			return;
+		}
+		/* Not yet processed - create new context and start fresh */
+		targetCtx = ExecRPRStartContext(winstate, pos);
+	}
+	else if (targetCtx->states == NULL)
+	{
+		/*
+		 * The head context already completed in an earlier call.  Reachable
+		 * under SKIP TO NEXT ROW, where overlapping contexts let one reach
+		 * FIN -- recording its result -- before the call for its own start
+		 * row arrives.  Register that result.
+		 */
+		goto register_result;
+	}
+
+	/*
+	 * Determine where to start processing. Usually nfaLastProcessedRow+1 >=
+	 * pos since contexts are created at currentPos+1 during processing.
+	 * However, pos can exceed this when rows are skipped (e.g., unmatched
+	 * rows don't update nfaLastProcessedRow).
+	 */
+	startPos = Max(pos, winstate->nfaLastProcessedRow + 1);
+
+	/*
+	 * Process rows until target context completes or we hit boundaries. Each
+	 * row evaluation is shared across all active contexts.
+	 */
+	for (currentPos = startPos; targetCtx->states != NULL; currentPos++)
+	{
+		bool		rowExists;
+
+		/*
+		 * Evaluate variables for this row - done only once, shared by all
+		 * contexts.
+		 *
+		 * Set nav_match_start to the head context's matchStartRow for
+		 * FIRST/LAST navigation.  Match_start-dependent variables (FIRST,
+		 * LAST-with-offset) are re-evaluated per-context in ExecRPRProcessRow
+		 * when matchStartRow differs.
+		 */
+		winstate->nav_match_start = targetCtx->matchStartRow;
+		rowExists = nfa_evaluate_row(winobj, currentPos, winstate->nfaVarMatched);
+
+		/* No more rows in partition? Finalize all contexts */
+		if (!rowExists)
+		{
+			ExecRPRFinalizeAllContexts(winstate, currentPos - 1);
+			/* Clean up dead contexts from finalization */
+			ExecRPRCleanupDeadContexts(winstate, targetCtx);
+			break;
+		}
+
+		/* Update last processed row */
+		winstate->nfaLastProcessedRow = currentPos;
+
+		/*--------------------------
+		 * Process all contexts for this row:
+		 *   1. Match all (convergence)
+		 *   2. Absorb redundant
+		 *   3. Advance all (divergence)
+		 */
+		ExecRPRProcessRow(winstate, currentPos, hasLimitedFrame, frameOffset);
+
+		/*
+		 * Create a new context for the next potential start position. This
+		 * enables overlapping match detection for SKIP TO NEXT ROW.
+		 */
+		ExecRPRStartContext(winstate, currentPos + 1);
+
+		/*
+		 * Clean up dead contexts (failed with no active states and no match).
+		 * This removes contexts that failed during processing and counts them
+		 * appropriately as pruned or mismatched.
+		 */
+		ExecRPRCleanupDeadContexts(winstate, targetCtx);
+	}
+
+register_result:
+	Assert(pos == targetCtx->matchStartRow);
+
+	/*
+	 * Record match result.
+	 */
+	winstate->rpr_match_valid = true;
+	winstate->rpr_match_start = targetCtx->matchStartRow;
+
+	if (targetCtx->matchEndRow < targetCtx->matchStartRow)
+	{
+		matchLen = targetCtx->lastProcessedRow - targetCtx->matchStartRow + 1;
+
+		if (targetCtx->matchedState != NULL)
+		{
+			/* Empty match: FIN reached but 0 rows consumed */
+			winstate->rpr_match_matched = true;
+			winstate->rpr_match_length = 0;
+			ExecRPRRecordContextSuccess(winstate, 0);
+		}
+		else
+		{
+			/* No match */
+			winstate->rpr_match_matched = false;
+			winstate->rpr_match_length = 1;
+			ExecRPRRecordContextFailure(winstate, matchLen);
+		}
+		ExecRPRFreeContext(winstate, targetCtx);
+		return;
+	}
+
+	/* Match succeeded */
+	matchLen = targetCtx->matchEndRow - targetCtx->matchStartRow + 1;
+
+	winstate->rpr_match_matched = true;
+	winstate->rpr_match_length = matchLen;
+	ExecRPRRecordContextSuccess(winstate, matchLen);
+
+	/* Remove the matched context */
+	ExecRPRFreeContext(winstate, targetCtx);
+}
+
+/*
+ * nfa_evaluate_row
+ *
+ * Evaluate all DEFINE variables for current row.
+ * Returns true if the row exists, false if out of partition.
+ * If row exists, fills varMatched array.
+ * varMatched[i] = true if variable i matched at current row.
+ *
+ * Uses 1-slot model: only ecxt_outertuple is set to the current row.
+ * PREV/NEXT/FIRST/LAST navigation is handled by EEOP_RPR_NAV_SET/RESTORE
+ * opcodes during expression evaluation, which temporarily swap the slot.
+ */
+static bool
+nfa_evaluate_row(WindowObject winobj, int64 pos, bool *varMatched)
+{
+	WindowAggState *winstate = winobj->winstate;
+	ExprContext *econtext = winstate->ss.ps.ps_ExprContext;
+	int			numDefineVars = list_length(winstate->defineVariableList);
+	int			varIdx = 0;
+	TupleTableSlot *slot;
+	int64		saved_pos;
+
+	/* Fetch current row into temp_slot_1 */
+	slot = winstate->temp_slot_1;
+	if (!window_gettupleslot(winobj, pos, slot))
+		return false;			/* No row exists */
+
+	/* Set up 1-slot context: only ecxt_outertuple */
+	econtext->ecxt_outertuple = slot;
+
+	/*
+	 * Save and set currentpos so that EEOP_RPR_NAV_SET opcodes can calculate
+	 * target positions (currentpos +/- offset).
+	 */
+	saved_pos = winstate->currentpos;
+	winstate->currentpos = pos;
+
+	/* Invalidate nav_slot cache so PREV/NEXT re-fetch for new row */
+	winstate->nav_slot_pos = -1;
+
+	foreach_ptr(ExprState, exprState, winstate->defineClauseList)
+	{
+		Datum		result;
+		bool		isnull;
+
+		/* Evaluate DEFINE expression */
+		result = ExecEvalExpr(exprState, econtext, &isnull);
+
+		varMatched[varIdx] = (!isnull && DatumGetBool(result));
+
+		varIdx++;
+		if (varIdx >= numDefineVars)
+			break;
+	}
+
+	winstate->currentpos = saved_pos;
+
+	return true;				/* Row exists */
+}
+
+/*
+ * WinGetSlotInFrame
+ * slot: TupleTableSlot to store the result
+ * relpos: signed rowcount offset from the seek position
+ * seektype: WINDOW_SEEK_HEAD or WINDOW_SEEK_TAIL
+ * set_mark: If the row is found/in frame and set_mark is true, the mark is
+ *		moved to the row as a side-effect.
+ * isnull: output argument, receives isnull status of result
+ * isout: output argument, set to indicate whether target row position
+ *		is out of frame (can pass NULL if caller doesn't care about this)
+ *
+ * Returns 0 if we successfully got the slot, or nonzero if out of frame.
+ * (isout is also set in the latter case.)
+ */
+static int
+WinGetSlotInFrame(WindowObject winobj, TupleTableSlot *slot,
+				  int relpos, int seektype, bool set_mark,
+				  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	int64		abs_pos;
+	int64		mark_pos;
+	int64		num_reduced_frame;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos + relpos;
+			mark_pos = abs_pos;
+
+			/*
+			 * Account for exclusion option if one is active, but advance only
+			 * abs_pos not mark_pos.  This prevents changes of the current
+			 * row's peer group from resulting in trying to fetch a row before
+			 * some previous mark position.
+			 *
+			 * Note that in some corner cases such as current row being
+			 * outside frame, these calculations are theoretically too simple,
+			 * but it doesn't matter because we'll end up deciding the row is
+			 * out of frame.  We do not attempt to avoid fetching rows past
+			 * end of frame; that would happen in some cases anyway.
+			 */
+			switch (winstate->frameOptions & FRAMEOPTION_EXCLUSION)
+			{
+				case 0:
+					/* no adjustment needed */
+					break;
+				case FRAMEOPTION_EXCLUDE_CURRENT_ROW:
+					if (abs_pos >= winstate->currentpos &&
+						winstate->currentpos >= winstate->frameheadpos)
+						abs_pos++;
+					break;
+				case FRAMEOPTION_EXCLUDE_GROUP:
+					update_grouptailpos(winstate);
+					if (abs_pos >= winstate->groupheadpos &&
+						winstate->grouptailpos > winstate->frameheadpos)
+					{
+						int64		overlapstart = Max(winstate->groupheadpos,
+													   winstate->frameheadpos);
+
+						abs_pos += winstate->grouptailpos - overlapstart;
+					}
+					break;
+				case FRAMEOPTION_EXCLUDE_TIES:
+					update_grouptailpos(winstate);
+					if (abs_pos >= winstate->groupheadpos &&
+						winstate->grouptailpos > winstate->frameheadpos)
+					{
+						int64		overlapstart = Max(winstate->groupheadpos,
+													   winstate->frameheadpos);
+
+						if (abs_pos == overlapstart)
+							abs_pos = winstate->currentpos;
+						else
+							abs_pos += winstate->grouptailpos - overlapstart - 1;
+					}
+					break;
+				default:
+					elog(ERROR, "unrecognized frame option state: 0x%x",
+						 winstate->frameOptions);
+					break;
+			}
+			num_reduced_frame = row_is_in_reduced_frame(winobj,
+														winstate->frameheadpos);
+			if (num_reduced_frame < 0)
+				goto out_of_frame;
+			else if (num_reduced_frame > 0)
+				if (relpos >= num_reduced_frame)
+					goto out_of_frame;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+
+			/*
+			 * RPR cares about frame head pos. Need to call
+			 * update_frameheadpos
+			 */
+			update_frameheadpos(winstate);
+
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1 + relpos;
+
+			/*
+			 * Account for exclusion option if one is active.  If there is no
+			 * exclusion, we can safely set the mark at the accessed row.  But
+			 * if there is, we can only mark the frame start, because we can't
+			 * be sure how far back in the frame the exclusion might cause us
+			 * to fetch in future.  Furthermore, we have to actually check
+			 * against frameheadpos here, since it's unsafe to try to fetch a
+			 * row before frame start if the mark might be there already.
+			 */
+			switch (winstate->frameOptions & FRAMEOPTION_EXCLUSION)
+			{
+				case 0:
+					/* no adjustment needed */
+					mark_pos = abs_pos;
+					break;
+				case FRAMEOPTION_EXCLUDE_CURRENT_ROW:
+					if (abs_pos <= winstate->currentpos &&
+						winstate->currentpos < winstate->frametailpos)
+						abs_pos--;
+					update_frameheadpos(winstate);
+					if (abs_pos < winstate->frameheadpos)
+						goto out_of_frame;
+					mark_pos = winstate->frameheadpos;
+					break;
+				case FRAMEOPTION_EXCLUDE_GROUP:
+					update_grouptailpos(winstate);
+					if (abs_pos < winstate->grouptailpos &&
+						winstate->groupheadpos < winstate->frametailpos)
+					{
+						int64		overlapend = Min(winstate->grouptailpos,
+													 winstate->frametailpos);
+
+						abs_pos -= overlapend - winstate->groupheadpos;
+					}
+					update_frameheadpos(winstate);
+					if (abs_pos < winstate->frameheadpos)
+						goto out_of_frame;
+					mark_pos = winstate->frameheadpos;
+					break;
+				case FRAMEOPTION_EXCLUDE_TIES:
+					update_grouptailpos(winstate);
+					if (abs_pos < winstate->grouptailpos &&
+						winstate->groupheadpos < winstate->frametailpos)
+					{
+						int64		overlapend = Min(winstate->grouptailpos,
+													 winstate->frametailpos);
+
+						if (abs_pos == overlapend - 1)
+							abs_pos = winstate->currentpos;
+						else
+							abs_pos -= overlapend - 1 - winstate->groupheadpos;
+					}
+					update_frameheadpos(winstate);
+					if (abs_pos < winstate->frameheadpos)
+						goto out_of_frame;
+					mark_pos = winstate->frameheadpos;
+					break;
+				default:
+					elog(ERROR, "unrecognized frame option state: 0x%x",
+						 winstate->frameOptions);
+					mark_pos = 0;	/* keep compiler quiet */
+					break;
+			}
+
+			num_reduced_frame = row_is_in_reduced_frame(winobj,
+														winstate->frameheadpos);
+			if (num_reduced_frame < 0)
+				goto out_of_frame;
+			else if (num_reduced_frame > 0)
+			{
+				if (-relpos >= num_reduced_frame)
+					goto out_of_frame;
+				abs_pos = winstate->frameheadpos + relpos +
+					num_reduced_frame - 1;
+			}
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	if (!window_gettupleslot(winobj, abs_pos, slot))
+		goto out_of_frame;
+
+	/* The code above does not detect all out-of-frame cases, so check */
+	if (row_is_in_frame(winobj, abs_pos, slot, false) <= 0)
+		goto out_of_frame;
+
+	if (isout)
+		*isout = false;
+	if (set_mark)
+	{
+		/*
+		 * If RPR is enabled and seek type is WINDOW_SEEK_TAIL, we set the
+		 * mark position unconditionally to frameheadpos. In this case the
+		 * frame always starts at CURRENT_ROW and never goes back, thus
+		 * setting the mark at the position is safe.
+		 */
+		if (winstate->rpPattern != NULL && seektype == WINDOW_SEEK_TAIL)
+			mark_pos = winstate->frameheadpos;
+		WinSetMarkPosition(winobj, mark_pos);
+	}
+	return 0;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return -1;
+}
+
+
+/***********************************************************************
+ * API exposed to window functions
+ ***********************************************************************/
+
+
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	Assert(WindowObjectIsValid(winobj));
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		const char *funcname = get_func_name(fcinfo->flinfo->fn_oid);
+
+		if (!funcname)
+			elog(ERROR, "could not get function name");
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("function %s does not allow RESPECT/IGNORE NULLS",
+						funcname)));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+}
+
+/*
+ * WinGetPartitionLocalMemory
+ *		Get working memory that lives till end of partition processing
+ *
+ * On first call within a given partition, this allocates and zeroes the
+ * requested amount of space.  Subsequent calls just return the same chunk.
+ *
+ * Memory obtained this way is normally used to hold state that should be
+ * automatically reset for each new partition.  If a window function wants
+ * to hold state across the whole query, fcinfo->fn_extra can be used in the
+ * usual way for that.
+ */
+void *
+WinGetPartitionLocalMemory(WindowObject winobj, Size sz)
+{
+	Assert(WindowObjectIsValid(winobj));
+	if (winobj->localmem == NULL)
+		winobj->localmem =
+			MemoryContextAllocZero(winobj->winstate->partcontext, sz);
+	return winobj->localmem;
+}
+
+/*
+ * WinGetCurrentPosition
+ *		Return the current row's position (counting from 0) within the current
+ *		partition.
+ */
+int64
+WinGetCurrentPosition(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->currentpos;
+}
+
+/*
+ * WinGetPartitionRowCount
+ *		Return total number of rows contained in the current partition.
+ *
+ * Note: this is a relatively expensive operation because it forces the
+ * whole partition to be "spooled" into the tuplestore at once.  Once
+ * executed, however, additional calls within the same partition are cheap.
+ */
+int64
+WinGetPartitionRowCount(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	spool_tuples(winobj->winstate, -1);
+	return winobj->winstate->spooled_rows;
 }
 
 /*
@@ -4001,8 +5212,6 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	WindowAggState *winstate;
 	ExprContext *econtext;
 	TupleTableSlot *slot;
-	int64		abs_pos;
-	int64		mark_pos;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
@@ -4013,166 +5222,15 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
 											 set_mark, isnull, isout);
 
-	switch (seektype)
+	if (WinGetSlotInFrame(winobj, slot,
+						  relpos, seektype, set_mark,
+						  isnull, isout) == 0)
 	{
-		case WINDOW_SEEK_CURRENT:
-			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
-			abs_pos = mark_pos = 0; /* keep compiler quiet */
-			break;
-		case WINDOW_SEEK_HEAD:
-			/* rejecting relpos < 0 is easy and simplifies code below */
-			if (relpos < 0)
-				goto out_of_frame;
-			update_frameheadpos(winstate);
-			abs_pos = winstate->frameheadpos + relpos;
-			mark_pos = abs_pos;
-
-			/*
-			 * Account for exclusion option if one is active, but advance only
-			 * abs_pos not mark_pos.  This prevents changes of the current
-			 * row's peer group from resulting in trying to fetch a row before
-			 * some previous mark position.
-			 *
-			 * Note that in some corner cases such as current row being
-			 * outside frame, these calculations are theoretically too simple,
-			 * but it doesn't matter because we'll end up deciding the row is
-			 * out of frame.  We do not attempt to avoid fetching rows past
-			 * end of frame; that would happen in some cases anyway.
-			 */
-			switch (winstate->frameOptions & FRAMEOPTION_EXCLUSION)
-			{
-				case 0:
-					/* no adjustment needed */
-					break;
-				case FRAMEOPTION_EXCLUDE_CURRENT_ROW:
-					if (abs_pos >= winstate->currentpos &&
-						winstate->currentpos >= winstate->frameheadpos)
-						abs_pos++;
-					break;
-				case FRAMEOPTION_EXCLUDE_GROUP:
-					update_grouptailpos(winstate);
-					if (abs_pos >= winstate->groupheadpos &&
-						winstate->grouptailpos > winstate->frameheadpos)
-					{
-						int64		overlapstart = Max(winstate->groupheadpos,
-													   winstate->frameheadpos);
-
-						abs_pos += winstate->grouptailpos - overlapstart;
-					}
-					break;
-				case FRAMEOPTION_EXCLUDE_TIES:
-					update_grouptailpos(winstate);
-					if (abs_pos >= winstate->groupheadpos &&
-						winstate->grouptailpos > winstate->frameheadpos)
-					{
-						int64		overlapstart = Max(winstate->groupheadpos,
-													   winstate->frameheadpos);
-
-						if (abs_pos == overlapstart)
-							abs_pos = winstate->currentpos;
-						else
-							abs_pos += winstate->grouptailpos - overlapstart - 1;
-					}
-					break;
-				default:
-					elog(ERROR, "unrecognized frame option state: 0x%x",
-						 winstate->frameOptions);
-					break;
-			}
-			break;
-		case WINDOW_SEEK_TAIL:
-			/* rejecting relpos > 0 is easy and simplifies code below */
-			if (relpos > 0)
-				goto out_of_frame;
-			update_frametailpos(winstate);
-			abs_pos = winstate->frametailpos - 1 + relpos;
-
-			/*
-			 * Account for exclusion option if one is active.  If there is no
-			 * exclusion, we can safely set the mark at the accessed row.  But
-			 * if there is, we can only mark the frame start, because we can't
-			 * be sure how far back in the frame the exclusion might cause us
-			 * to fetch in future.  Furthermore, we have to actually check
-			 * against frameheadpos here, since it's unsafe to try to fetch a
-			 * row before frame start if the mark might be there already.
-			 */
-			switch (winstate->frameOptions & FRAMEOPTION_EXCLUSION)
-			{
-				case 0:
-					/* no adjustment needed */
-					mark_pos = abs_pos;
-					break;
-				case FRAMEOPTION_EXCLUDE_CURRENT_ROW:
-					if (abs_pos <= winstate->currentpos &&
-						winstate->currentpos < winstate->frametailpos)
-						abs_pos--;
-					update_frameheadpos(winstate);
-					if (abs_pos < winstate->frameheadpos)
-						goto out_of_frame;
-					mark_pos = winstate->frameheadpos;
-					break;
-				case FRAMEOPTION_EXCLUDE_GROUP:
-					update_grouptailpos(winstate);
-					if (abs_pos < winstate->grouptailpos &&
-						winstate->groupheadpos < winstate->frametailpos)
-					{
-						int64		overlapend = Min(winstate->grouptailpos,
-													 winstate->frametailpos);
-
-						abs_pos -= overlapend - winstate->groupheadpos;
-					}
-					update_frameheadpos(winstate);
-					if (abs_pos < winstate->frameheadpos)
-						goto out_of_frame;
-					mark_pos = winstate->frameheadpos;
-					break;
-				case FRAMEOPTION_EXCLUDE_TIES:
-					update_grouptailpos(winstate);
-					if (abs_pos < winstate->grouptailpos &&
-						winstate->groupheadpos < winstate->frametailpos)
-					{
-						int64		overlapend = Min(winstate->grouptailpos,
-													 winstate->frametailpos);
-
-						if (abs_pos == overlapend - 1)
-							abs_pos = winstate->currentpos;
-						else
-							abs_pos -= overlapend - 1 - winstate->groupheadpos;
-					}
-					update_frameheadpos(winstate);
-					if (abs_pos < winstate->frameheadpos)
-						goto out_of_frame;
-					mark_pos = winstate->frameheadpos;
-					break;
-				default:
-					elog(ERROR, "unrecognized frame option state: 0x%x",
-						 winstate->frameOptions);
-					mark_pos = 0;	/* keep compiler quiet */
-					break;
-			}
-			break;
-		default:
-			elog(ERROR, "unrecognized window seek type: %d", seektype);
-			abs_pos = mark_pos = 0; /* keep compiler quiet */
-			break;
+		econtext->ecxt_outertuple = slot;
+		return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							econtext, isnull);
 	}
 
-	if (!window_gettupleslot(winobj, abs_pos, slot))
-		goto out_of_frame;
-
-	/* The code above does not detect all out-of-frame cases, so check */
-	if (row_is_in_frame(winobj, abs_pos, slot, false) <= 0)
-		goto out_of_frame;
-
-	if (isout)
-		*isout = false;
-	if (set_mark)
-		WinSetMarkPosition(winobj, mark_pos);
-	econtext->ecxt_outertuple = slot;
-	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
-						econtext, isnull);
-
-out_of_frame:
 	if (isout)
 		*isout = true;
 	*isnull = true;
diff --git a/src/backend/jit/llvm/llvmjit_expr.c b/src/backend/jit/llvm/llvmjit_expr.c
index 0e160b8502c..e42c5d65bb6 100644
--- a/src/backend/jit/llvm/llvmjit_expr.c
+++ b/src/backend/jit/llvm/llvmjit_expr.c
@@ -129,6 +129,9 @@ llvm_compile_expr(ExprState *state)
 	LLVMValueRef v_aggvalues;
 	LLVMValueRef v_aggnulls;
 
+	/* RPR navigation: when true, EEOP_OUTER_VAR reloads from econtext */
+	bool		has_rpr_nav;
+
 	instr_time	starttime;
 	instr_time	deform_starttime;
 	instr_time	endtime;
@@ -298,6 +301,36 @@ llvm_compile_expr(ExprState *state)
 								   FIELDNO_EXPRCONTEXT_AGGNULLS,
 								   "v.econtext.aggnulls");
 
+	/*
+	 * RPR navigation opcodes (PREV/NEXT) swap ecxt_outertuple to a different
+	 * row mid-expression.  The JIT code loads v_outervalues and v_outernulls
+	 * once in the entry block and reuses them for all EEOP_OUTER_VAR steps.
+	 * After a slot swap, these cached pointers become stale because the new
+	 * slot has its own tts_values/tts_isnull arrays.
+	 *
+	 * When RPR navigation opcodes are present, EEOP_OUTER_VAR reloads the
+	 * slot pointer from econtext->ecxt_outertuple on every access instead of
+	 * using the cached entry-block values.  This avoids the SSA/PHI
+	 * complexity while keeping the rest of the expression JIT-compiled.
+	 * Expressions without RPR navigation use the cached values as before.
+	 */
+	has_rpr_nav = false;
+	if (parent && IsA(parent, WindowAggState) &&
+		((WindowAgg *) parent->plan)->rpPattern != NULL)
+	{
+		for (int opno = 0; opno < state->steps_len; opno++)
+		{
+			ExprEvalOp	opcode = ExecEvalStepOp(state, &state->steps[opno]);
+
+			if (opcode == EEOP_RPR_NAV_SET ||
+				opcode == EEOP_RPR_NAV_RESTORE)
+			{
+				has_rpr_nav = true;
+				break;
+			}
+		}
+	}
+
 	/* allocate blocks for each op upfront, so we can do jumps easily */
 	opblocks = palloc_array(LLVMBasicBlockRef, state->steps_len);
 	for (int opno = 0; opno < state->steps_len; opno++)
@@ -460,8 +493,37 @@ llvm_compile_expr(ExprState *state)
 					}
 					else if (opcode == EEOP_OUTER_VAR)
 					{
-						v_values = v_outervalues;
-						v_nulls = v_outernulls;
+						if (has_rpr_nav)
+						{
+							/*
+							 * RPR navigation swaps ecxt_outertuple
+							 * mid-expression.  Reload slot pointer from
+							 * econtext on every access so we read from the
+							 * current (possibly swapped) slot.
+							 */
+							LLVMValueRef v_tmpslot;
+
+							v_tmpslot = l_load_struct_gep(b,
+														  StructExprContext,
+														  v_econtext,
+														  FIELDNO_EXPRCONTEXT_OUTERTUPLE,
+														  "v_outerslot_reload");
+							v_values = l_load_struct_gep(b,
+														 StructTupleTableSlot,
+														 v_tmpslot,
+														 FIELDNO_TUPLETABLESLOT_VALUES,
+														 "v_outervalues_reload");
+							v_nulls = l_load_struct_gep(b,
+														StructTupleTableSlot,
+														v_tmpslot,
+														FIELDNO_TUPLETABLESLOT_ISNULL,
+														"v_outernulls_reload");
+						}
+						else
+						{
+							v_values = v_outervalues;
+							v_nulls = v_outernulls;
+						}
 					}
 					else if (opcode == EEOP_SCAN_VAR)
 					{
@@ -2434,6 +2496,18 @@ llvm_compile_expr(ExprState *state)
 				LLVMBuildBr(b, opblocks[opno + 1]);
 				break;
 
+			case EEOP_RPR_NAV_SET:
+				build_EvalXFunc(b, mod, "ExecEvalRPRNavSet",
+								v_state, op, v_econtext);
+				LLVMBuildBr(b, opblocks[opno + 1]);
+				break;
+
+			case EEOP_RPR_NAV_RESTORE:
+				build_EvalXFunc(b, mod, "ExecEvalRPRNavRestore",
+								v_state, op, v_econtext);
+				LLVMBuildBr(b, opblocks[opno + 1]);
+				break;
+
 			case EEOP_AGG_STRICT_DESERIALIZE:
 			case EEOP_AGG_DESERIALIZE:
 				{
diff --git a/src/backend/jit/llvm/llvmjit_types.c b/src/backend/jit/llvm/llvmjit_types.c
index c8a1f841293..e78b31d775f 100644
--- a/src/backend/jit/llvm/llvmjit_types.c
+++ b/src/backend/jit/llvm/llvmjit_types.c
@@ -168,6 +168,8 @@ void	   *referenced_functions[] =
 	ExecEvalScalarArrayOp,
 	ExecEvalHashedScalarArrayOp,
 	ExecEvalSubPlan,
+	ExecEvalRPRNavSet,
+	ExecEvalRPRNavRestore,
 	ExecEvalSysVar,
 	ExecEvalWholeRowVar,
 	ExecEvalXmlExpr,
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index 78b7f05aba2..3869f6c8994 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -41,7 +41,6 @@ static bool rank_up(WindowObject winobj);
 static Datum leadlag_common(FunctionCallInfo fcinfo,
 							bool forward, bool withoffset, bool withdefault);
 
-
 /*
  * utility routine for *_rank functions.
  */
@@ -724,3 +723,121 @@ window_nth_value(PG_FUNCTION_ARGS)
 
 	PG_RETURN_DATUM(result);
 }
+
+/*
+ * prev
+ * Catalog placeholder for RPR's PREV navigation operator.
+ *
+ * The parser transforms prev() calls inside DEFINE into RPRNavExpr nodes,
+ * so this function is never reached during normal RPR execution.  It exists
+ * only so that the parser can resolve the function name from pg_proc.
+ * Calls outside DEFINE are rejected by parse_func.c (EXPR_KIND_RPR_DEFINE
+ * check).  The error below is a defensive measure in case that check is
+ * bypassed (e.g., direct C-level function invocation).
+ */
+Datum
+window_prev(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			errmsg("cannot use PREV() outside a DEFINE clause"));
+	PG_RETURN_NULL();			/* not reached */
+}
+
+/*
+ * next
+ * Catalog placeholder for RPR's NEXT navigation operator.
+ * See window_prev() for details.
+ */
+Datum
+window_next(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			errmsg("cannot use NEXT() outside a DEFINE clause"));
+	PG_RETURN_NULL();			/* not reached */
+}
+
+/*
+ * prev(value, offset)
+ * Catalog placeholder for RPR's PREV navigation operator with offset.
+ * See window_prev() for details.
+ */
+Datum
+window_prev_offset(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			errmsg("cannot use PREV() outside a DEFINE clause"));
+	PG_RETURN_NULL();			/* not reached */
+}
+
+/*
+ * next(value, offset)
+ * Catalog placeholder for RPR's NEXT navigation operator with offset.
+ * See window_prev() for details.
+ */
+Datum
+window_next_offset(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			errmsg("cannot use NEXT() outside a DEFINE clause"));
+	PG_RETURN_NULL();			/* not reached */
+}
+
+/*
+ * first
+ * Catalog placeholder for RPR's FIRST navigation operator.
+ * See window_prev() for details.
+ */
+Datum
+window_first(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			errmsg("cannot use FIRST() outside a DEFINE clause"));
+	PG_RETURN_NULL();			/* not reached */
+}
+
+/*
+ * last
+ * Catalog placeholder for RPR's LAST navigation operator.
+ * See window_prev() for details.
+ */
+Datum
+window_last(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			errmsg("cannot use LAST() outside a DEFINE clause"));
+	PG_RETURN_NULL();			/* not reached */
+}
+
+/*
+ * first(value, offset)
+ * Catalog placeholder for RPR's FIRST navigation operator with offset.
+ * See window_prev() for details.
+ */
+Datum
+window_first_offset(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			errmsg("cannot use FIRST() outside a DEFINE clause"));
+	PG_RETURN_NULL();			/* not reached */
+}
+
+/*
+ * last(value, offset)
+ * Catalog placeholder for RPR's LAST navigation operator with offset.
+ * See window_prev() for details.
+ */
+Datum
+window_last_offset(PG_FUNCTION_ARGS)
+{
+	ereport(ERROR,
+			errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			errmsg("cannot use LAST() outside a DEFINE clause"));
+	PG_RETURN_NULL();			/* not reached */
+}
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index be157a5fbe9..b3aa42fc66e 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10967,6 +10967,30 @@
 { oid => '3114', descr => 'fetch the Nth row value',
   proname => 'nth_value', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4', prosrc => 'window_nth_value' },
+{ oid => '8126', descr => 'fetch the preceding row value',
+  proname => 'prev', provolatile => 's', prorettype => 'anyelement',
+  proargtypes => 'anyelement', prosrc => 'window_prev' },
+{ oid => '8128', descr => 'fetch the Nth preceding row value',
+  proname => 'prev', provolatile => 's', proisstrict => 'f', prorettype => 'anyelement',
+  proargtypes => 'anyelement int8', prosrc => 'window_prev_offset' },
+{ oid => '8127', descr => 'fetch the following row value',
+  proname => 'next', provolatile => 's', prorettype => 'anyelement',
+  proargtypes => 'anyelement', prosrc => 'window_next' },
+{ oid => '8129', descr => 'fetch the Nth following row value',
+  proname => 'next', provolatile => 's', proisstrict => 'f', prorettype => 'anyelement',
+  proargtypes => 'anyelement int8', prosrc => 'window_next_offset' },
+{ oid => '8130', descr => 'fetch the first row value within match',
+  proname => 'first', provolatile => 's', prorettype => 'anyelement',
+  proargtypes => 'anyelement', prosrc => 'window_first' },
+{ oid => '8132', descr => 'fetch the Nth row value within match',
+  proname => 'first', provolatile => 's', proisstrict => 'f', prorettype => 'anyelement',
+  proargtypes => 'anyelement int8', prosrc => 'window_first_offset' },
+{ oid => '8131', descr => 'fetch the last row value within match',
+  proname => 'last', provolatile => 's', prorettype => 'anyelement',
+  proargtypes => 'anyelement', prosrc => 'window_last' },
+{ oid => '8133', descr => 'fetch the Nth-from-last row value within match',
+  proname => 'last', provolatile => 's', proisstrict => 'f', prorettype => 'anyelement',
+  proargtypes => 'anyelement int8', prosrc => 'window_last_offset' },
 
 # functions for range types
 { oid => '3832', descr => 'I/O',
diff --git a/src/include/executor/execExpr.h b/src/include/executor/execExpr.h
index c61b3d624d5..db66ebe313c 100644
--- a/src/include/executor/execExpr.h
+++ b/src/include/executor/execExpr.h
@@ -274,6 +274,10 @@ typedef enum ExprEvalOp
 	EEOP_MERGE_SUPPORT_FUNC,
 	EEOP_SUBPLAN,
 
+	/* row pattern navigation (RPR PREV/NEXT) */
+	EEOP_RPR_NAV_SET,
+	EEOP_RPR_NAV_RESTORE,
+
 	/* aggregation related nodes */
 	EEOP_AGG_STRICT_DESERIALIZE,
 	EEOP_AGG_DESERIALIZE,
@@ -695,6 +699,18 @@ typedef struct ExprEvalStep
 			SubPlanState *sstate;
 		}			subplan;
 
+		/* for EEOP_RPR_NAV_SET / EEOP_RPR_NAV_RESTORE */
+		struct
+		{
+			WindowAggState *winstate;
+			RPRNavKind	kind;	/* navigation kind (simple or compound) */
+			Datum	   *offset_value;	/* offset value(s), or NULL */
+			bool	   *offset_isnull;	/* offset null flag(s) */
+			/* For compound nav: offset_value[0] = inner, [1] = outer */
+			int16		resulttyplen;	/* RESTORE: result type length */
+			bool		resulttypbyval; /* RESTORE: result pass-by-value? */
+		}			rpr_nav;
+
 		/* for EEOP_AGG_*DESERIALIZE */
 		struct
 		{
@@ -902,6 +918,10 @@ extern void ExecEvalMergeSupportFunc(ExprState *state, ExprEvalStep *op,
 									 ExprContext *econtext);
 extern void ExecEvalSubPlan(ExprState *state, ExprEvalStep *op,
 							ExprContext *econtext);
+extern void ExecEvalRPRNavSet(ExprState *state, ExprEvalStep *op,
+							  ExprContext *econtext);
+extern void ExecEvalRPRNavRestore(ExprState *state, ExprEvalStep *op,
+								  ExprContext *econtext);
 extern void ExecEvalWholeRowVar(ExprState *state, ExprEvalStep *op,
 								ExprContext *econtext);
 extern void ExecEvalSysVar(ExprState *state, ExprEvalStep *op,
diff --git a/src/include/executor/execRPR.h b/src/include/executor/execRPR.h
new file mode 100644
index 00000000000..7b2b0febb76
--- /dev/null
+++ b/src/include/executor/execRPR.h
@@ -0,0 +1,40 @@
+/*-------------------------------------------------------------------------
+ *
+ * execRPR.h
+ *	  prototypes for execRPR.c (NFA-based Row Pattern Recognition engine)
+ *
+ *
+ * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/execRPR.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef EXECRPR_H
+#define EXECRPR_H
+
+#include "nodes/execnodes.h"
+#include "windowapi.h"
+
+/* NFA context management */
+extern RPRNFAContext *ExecRPRStartContext(WindowAggState *winstate,
+										  int64 startPos);
+extern RPRNFAContext *ExecRPRGetHeadContext(WindowAggState *winstate,
+											int64 pos);
+extern void ExecRPRFreeContext(WindowAggState *winstate, RPRNFAContext *ctx);
+
+/* NFA processing */
+extern void ExecRPRProcessRow(WindowAggState *winstate, int64 currentPos,
+							  bool hasLimitedFrame, int64 frameOffset);
+extern void ExecRPRCleanupDeadContexts(WindowAggState *winstate,
+									   RPRNFAContext *excludeCtx);
+extern void ExecRPRFinalizeAllContexts(WindowAggState *winstate, int64 lastPos);
+
+/* NFA statistics */
+extern void ExecRPRRecordContextSuccess(WindowAggState *winstate,
+										int64 matchLen);
+extern void ExecRPRRecordContextFailure(WindowAggState *winstate,
+										int64 failedLen);
+
+#endif							/* EXECRPR_H */
diff --git a/src/include/executor/nodeWindowAgg.h b/src/include/executor/nodeWindowAgg.h
index ada4a1c458c..f6f6645131c 100644
--- a/src/include/executor/nodeWindowAgg.h
+++ b/src/include/executor/nodeWindowAgg.h
@@ -20,4 +20,7 @@ extern WindowAggState *ExecInitWindowAgg(WindowAgg *node, EState *estate, int ef
 extern void ExecEndWindowAgg(WindowAggState *node);
 extern void ExecReScanWindowAgg(WindowAggState *node);
 
+/* RPR navigation support for expression evaluation opcodes */
+extern TupleTableSlot *ExecRPRNavGetSlot(WindowAggState *winstate, int64 pos);
+
 #endif							/* NODEWINDOWAGG_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 53c138310db..792aa3f0d05 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -38,6 +38,9 @@
 #include "nodes/plannodes.h"
 #include "partitioning/partdefs.h"
 #include "storage/buf.h"
+#include "storage/condition_variable.h"
+#include "utils/hsearch.h"
+#include "utils/queryenvironment.h"
 #include "utils/reltrigger.h"
 #include "utils/typcache.h"
 
@@ -2525,6 +2528,71 @@ typedef enum WindowAggStatus
 									 * tuples during spool */
 } WindowAggStatus;
 
+/* RPR reduced frame states returned by get_reduced_frame_status() */
+#define RF_NOT_DETERMINED	0	/* not yet processed */
+#define RF_FRAME_HEAD		1	/* start row of a match */
+#define RF_SKIPPED			2	/* interior row of a match */
+#define RF_UNMATCHED		3	/* no match at this row */
+#define RF_EMPTY_MATCH		4	/* empty match (0 rows); treated as unmatched */
+
+/*
+ * RPRNFAState - single NFA state for pattern matching
+ *
+ * counts[] tracks repetition counts at each nesting depth.
+ *
+ * isAbsorbable tracks if state is in absorbable region (ABSORBABLE_BRANCH).
+ * Monotonic property: once false, stays false (can't re-enter region).
+ */
+typedef struct RPRNFAState
+{
+	struct RPRNFAState *next;	/* next state in linked list */
+	int16		elemIdx;		/* current pattern element index */
+	bool		isAbsorbable;	/* true if state is in absorbable region */
+	int32		counts[FLEXIBLE_ARRAY_MEMBER];	/* repetition counts by depth */
+} RPRNFAState;
+
+/*
+ * RPRNFAContext - context for NFA pattern matching execution
+ *
+ * Two-flag absorption design:
+ *   hasAbsorbableState: can this context absorb others? (>=1 absorbable state)
+ *     - Monotonic: true->false only, cannot recover once false
+ *     - Used to skip absorption attempts once all absorbable states are gone
+ *   allStatesAbsorbable: can this context be absorbed? (ALL states absorbable)
+ *     - Dynamic: can change false->true (when non-absorbable states die)
+ *     - Used to determine if this context is eligible for absorption
+ */
+typedef struct RPRNFAContext
+{
+	struct RPRNFAContext *next; /* next context in linked list */
+	struct RPRNFAContext *prev; /* previous context (for reverse traversal) */
+	RPRNFAState *states;		/* active states (linked list) */
+
+	int64		matchStartRow;	/* row where match started */
+	int64		matchEndRow;	/* row where match ended (-1 = no match) */
+	int64		lastProcessedRow;	/* last row processed (for fail depth) */
+	RPRNFAState *matchedState;	/* FIN state for greedy fallback (cloned) */
+
+	/* Two-flag absorption optimization */
+	bool		hasAbsorbableState; /* can absorb others (>=1 absorbable
+									 * state) */
+	bool		allStatesAbsorbable;	/* can be absorbed (ALL states
+										 * absorbable) */
+} RPRNFAContext;
+
+/*
+ * NFALengthStats
+ *
+ * Statistics for length measurements (min/max/total) used for computing
+ * average lengths in EXPLAIN ANALYZE output.
+ */
+typedef struct NFALengthStats
+{
+	int64		min;			/* minimum length */
+	int64		max;			/* maximum length */
+	int64		total;			/* total length (for computing average) */
+} NFALengthStats;
+
 typedef struct WindowAggState
 {
 	ScanState	ss;				/* its first field is NodeTag */
@@ -2584,6 +2652,51 @@ typedef struct WindowAggState
 	int64		groupheadpos;	/* current row's peer group head position */
 	int64		grouptailpos;	/* " " " " tail position (group end+1) */
 
+	/* these fields are used in Row pattern recognition: */
+	RPSkipTo	rpSkipTo;		/* Row Pattern Skip To type */
+	struct RPRPattern *rpPattern;	/* compiled pattern for NFA execution */
+	List	   *defineVariableList; /* list of row pattern definition
+									 * variables (list of String) */
+	List	   *defineClauseList;	/* expression for row pattern definition
+									 * search conditions ExprState list */
+	RPRNFAContext *nfaContext;	/* active matching contexts (head) */
+	RPRNFAContext *nfaContextTail;	/* tail of active contexts (for reverse
+									 * traversal) */
+	RPRNFAContext *nfaContextFree;	/* recycled NFA context nodes */
+	RPRNFAState *nfaStateFree;	/* recycled NFA state nodes */
+	Size		nfaStateSize;	/* pre-calculated RPRNFAState size */
+	bool	   *nfaVarMatched;	/* per-row cache: varMatched[varId] for varId
+								 * < numDefines */
+	Bitmapset  *defineMatchStartDependent;	/* DEFINE vars needing per-context
+											 * evaluation
+											 * (match_start-dependent) */
+	bitmapword *nfaVisitedElems;	/* elemIdx visited bitmap for cycle
+									 * detection */
+	int16		nfaVisitedMinWord;	/* lowest bitmapword index touched since
+									 * last reset (PG_INT16_MAX = none) */
+	int16		nfaVisitedMaxWord;	/* highest bitmapword index touched since
+									 * last reset (-1 = none) */
+	int64		nfaLastProcessedRow;	/* last row processed by NFA (-1 =
+										 * none) */
+
+	/* NFA statistics for EXPLAIN ANALYZE */
+	int64		nfaStatesActive;	/* current active states (internal) */
+	int64		nfaStatesMax;	/* peak active states */
+	int64		nfaStatesTotalCreated;	/* total states allocated */
+	int64		nfaStatesMerged;	/* states merged (deduplicated) */
+	int64		nfaContextsActive;	/* current active contexts (internal) */
+	int64		nfaContextsMax; /* peak active contexts */
+	int64		nfaContextsTotalCreated;	/* total contexts allocated */
+	int64		nfaContextsAbsorbed;	/* contexts absorbed (optimization) */
+	int64		nfaContextsSkipped; /* contexts skipped (SKIP PAST LAST ROW) */
+	int64		nfaContextsPruned;	/* contexts pruned on first row */
+	int64		nfaMatchesSucceeded;	/* successful pattern matches */
+	int64		nfaMatchesFailed;	/* failed pattern matches */
+	NFALengthStats nfaMatchLen; /* successful match length stats */
+	NFALengthStats nfaFailLen;	/* mismatch length stats */
+	NFALengthStats nfaAbsorbedLen;	/* absorbed context length stats */
+	NFALengthStats nfaSkippedLen;	/* skipped context length stats */
+
 	MemoryContext partcontext;	/* context for partition-lifespan data */
 	MemoryContext aggcontext;	/* shared context for aggregate working data */
 	MemoryContext curaggcontext;	/* current aggregate's working data */
@@ -2611,6 +2724,25 @@ typedef struct WindowAggState
 	TupleTableSlot *agg_row_slot;
 	TupleTableSlot *temp_slot_1;
 	TupleTableSlot *temp_slot_2;
+
+	/* RPR navigation */
+	RPRNavOffsetKind navMaxOffsetKind;	/* status of navMaxOffset */
+	int64		navMaxOffset;	/* max backward nav offset (when FIXED) */
+	bool		hasFirstNav;	/* FIRST() present in DEFINE */
+	RPRNavOffsetKind navFirstOffsetKind;	/* status of navFirstOffset */
+	int64		navFirstOffset; /* min FIRST() offset (when FIXED) */
+	struct WindowObjectData *nav_winobj;	/* winobj for RPR nav fetch */
+	int64		nav_slot_pos;	/* position cached in nav_slot, or -1 */
+	TupleTableSlot *nav_slot;	/* slot for PREV/NEXT/FIRST/LAST target row */
+	TupleTableSlot *nav_saved_outertuple;	/* saved slot during nav swap */
+	TupleTableSlot *nav_null_slot;	/* all NULL slot */
+	int64		nav_match_start;	/* match_start for FIRST/LAST nav */
+
+	/* RPR current match result */
+	bool		rpr_match_valid;	/* true if a match result is set */
+	bool		rpr_match_matched;	/* true if the result was a match */
+	int64		rpr_match_start;	/* start position of the match result */
+	int64		rpr_match_length;	/* number of rows matched (0 = empty) */
 } WindowAggState;
 
 /* ----------------
-- 
2.43.0

