Re: Row pattern recognition - Mailing list pgsql-hackers

Hi Henson,

> Hi Tatsuo,
> 
> Here are six incremental patches on top of v43.
> 
> nocfbot-0001 through nocfbot-0004 are the same patches from the
> previous round (32-bit test fix, PREV/NEXT restriction, ALT lexical
> ordering, reluctant quantifiers).
> 
> nocfbot-0005: Detect zero-consumption NFA cycles
> 
> Adds a per-element visited bitmap to detect zero-consumption cycles
> during DFS epsilon expansion.  Before each state's DFS, the bitmap
> is cleared; as nfa_advance_state() recurses through epsilon
> transitions, each elemIdx is marked visited.  If the same elemIdx
> is reached again within the same DFS, it means an epsilon-only
> loop -- the state is freed immediately.
> 
> The ad-hoc (count == 0 && min == 0) exit condition in
> nfa_advance_end() is removed.  The FIXME test cases are resolved
> and renamed to "Zero-Consumption Cycle Detection".
> 
> nocfbot-0006: Allow A{0} quantifier
> 
> With cycle detection in place, this becomes straightforward.
> Lowers the {n} bound minimum from 1 to 0.  A{0} is treated as an
> epsilon transition -- the variable is skipped entirely.

Great!

> Next I plan to work on test reorganization, cross-database result
> comparison, and a review pass over the NFA executor.

Looking forward to seeing next patches.

BTW, in create_windowagg_plan (createplan.c),
around:
/* Build RPR pattern and filter defineClause */

collectPatternVariables, filterDefineClause and buildRPRPattern are
called in a block without any if or any other conditional
statements. This is an unusual codiing style in PostgreSQL.  I suggest
to fix this.  Attached is a proposed patch for this.

Best regards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index bbc2c7e71f4..e7aafc89700 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -2484,6 +2484,10 @@ create_windowagg_plan(PlannerInfo *root, WindowAggPath *best_path)
     Oid           *ordOperators;
     Oid           *ordCollations;
     ListCell   *lc;
+    List       *defineVariableList = NIL;
+    List       *filteredDefineClause = NIL;
+    RPRPattern *compiledPattern = NULL;
+
 
     /*
      * Choice of tlist here is motivated by the fact that WindowAgg will be
@@ -2535,50 +2539,45 @@ create_windowagg_plan(PlannerInfo *root, WindowAggPath *best_path)
     }
 
     /* Build RPR pattern and filter defineClause */
+    if (wc->rpPattern)
     {
-        List       *defineVariableList = NIL;
-        List       *filteredDefineClause = NIL;
-        RPRPattern *compiledPattern = NULL;
-
-        if (wc->rpPattern)
-        {
-            List       *patternVars;
+        List       *patternVars;
 
-            /*
-             * Filter defineClause to include only variables used in PATTERN.
-             * This eliminates unnecessary DEFINE evaluations at runtime.
-             */
-            patternVars = collectPatternVariables(wc->rpPattern);
-            filteredDefineClause = filterDefineClause(wc->defineClause,
-                                                      patternVars,
-                                                      &defineVariableList);
-
-            compiledPattern = buildRPRPattern(wc->rpPattern,
-                                              defineVariableList,
-                                              wc->rpSkipTo,
-                                              wc->frameOptions);
-        }
-
-        /* And finally we can make the WindowAgg node */
-        plan = make_windowagg(tlist,
-                              wc,
-                              partNumCols,
-                              partColIdx,
-                              partOperators,
-                              partCollations,
-                              ordNumCols,
-                              ordColIdx,
-                              ordOperators,
-                              ordCollations,
-                              best_path->runCondition,
-                              wc->rpSkipTo,
-                              compiledPattern,
-                              filteredDefineClause,
-                              best_path->qual,
-                              best_path->topwindow,
-                              subplan);
+        /*
+         * Filter defineClause to include only variables used in PATTERN. This
+         * eliminates unnecessary DEFINE evaluations at runtime.
+         */
+        patternVars = collectPatternVariables(wc->rpPattern);
+        filteredDefineClause = filterDefineClause(wc->defineClause,
+                                                  patternVars,
+                                                  &defineVariableList);
+
+        /* Compile and optimize RPR patterns */
+        compiledPattern = buildRPRPattern(wc->rpPattern,
+                                          defineVariableList,
+                                          wc->rpSkipTo,
+                                          wc->frameOptions);
     }
 
+    /* And finally we can make the WindowAgg node */
+    plan = make_windowagg(tlist,
+                          wc,
+                          partNumCols,
+                          partColIdx,
+                          partOperators,
+                          partCollations,
+                          ordNumCols,
+                          ordColIdx,
+                          ordOperators,
+                          ordCollations,
+                          best_path->runCondition,
+                          wc->rpSkipTo,
+                          compiledPattern,
+                          filteredDefineClause,
+                          best_path->qual,
+                          best_path->topwindow,
+                          subplan);
+
     copy_generic_path_info(&plan->plan, (Path *) best_path);
 
     return plan;