Re: BUG #17088: FailedAssertion in prepagg.c - Mailing list pgsql-bugs

Kyotaro Horiguchi <horikyota.ntt@gmail.com> writes:
> At Fri, 9 Jul 2021 14:54:02 +0800, Richard Guo <guofenglinux@gmail.com> wrote in
>> Update the patch with comments and test cases.

> AFAICS the patch looks correct.  It works for the first example and
> the two from Tom.  I don't find other place that has the similar
> issue.

I'd been expecting Andrew to pick this up, but since he hasn't,
I took a look.

I concur that the core problem is that GroupingFunc has to be treated
almost exactly like Aggref, and here we have a couple of places that
didn't get that memo.  So it occurred to me to look for other places
that special-case Aggref and don't have parallel code for GroupingFunc,
and I found several:

expression_returns_set_walker

This isn't particularly hazardous, since the argument (probably?) can't
contain a SRF, but it still seems like it ought to treat the two node
types the same.

cost_qual_eval_walker

It's defaulting to charging the eval costs of the arguments, which is
flat wrong.  I made it charge one cpu_operator_cost instead.

ruleutils.c

Various places concerned with whether or not we need parens were
making the wrong choice, resulting in excess parens in pretty-printing
mode.  This is also just cosmetic, but still.

This looks good to me now, and I'll set about back-patching.

            regards, tom lane

diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 47d0564fa2..ec25aae6e3 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -736,6 +736,8 @@ expression_returns_set_walker(Node *node, void *context)
     /* Avoid recursion for some cases that parser checks not to return a set */
     if (IsA(node, Aggref))
         return false;
+    if (IsA(node, GroupingFunc))
+        return false;
     if (IsA(node, WindowFunc))
         return false;

diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 8dc7dd4ca2..4d9f3b4bb6 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -4492,6 +4492,12 @@ cost_qual_eval_walker(Node *node, cost_qual_eval_context *context)
          */
         return false;            /* don't recurse into children */
     }
+    else if (IsA(node, GroupingFunc))
+    {
+        /* Treat this as having cost 1 */
+        context->total.per_tuple += cpu_operator_cost;
+        return false;            /* don't recurse into children */
+    }
     else if (IsA(node, CoerceViaIO))
     {
         CoerceViaIO *iocoerce = (CoerceViaIO *) node;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 41bd1ae7d4..863e0e24a1 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -356,15 +356,17 @@ build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
         Node       *arg = pitem->item;

         /*
-         * The Var, PlaceHolderVar, or Aggref has already been adjusted to
-         * have the correct varlevelsup, phlevelsup, or agglevelsup.
+         * The Var, PlaceHolderVar, Aggref or GroupingFunc has already been
+         * adjusted to have the correct varlevelsup, phlevelsup, or
+         * agglevelsup.
          *
-         * If it's a PlaceHolderVar or Aggref, its arguments might contain
-         * SubLinks, which have not yet been processed (see the comments for
-         * SS_replace_correlation_vars).  Do that now.
+         * If it's a PlaceHolderVar, Aggref or GroupingFunc, its arguments
+         * might contain SubLinks, which have not yet been processed (see the
+         * comments for SS_replace_correlation_vars).  Do that now.
          */
         if (IsA(arg, PlaceHolderVar) ||
-            IsA(arg, Aggref))
+            IsA(arg, Aggref) ||
+            IsA(arg, GroupingFunc))
             arg = SS_process_sublinks(root, arg, false);

         splan->parParam = lappend_int(splan->parParam, pitem->paramId);
@@ -1957,10 +1959,11 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
     }

     /*
-     * Don't recurse into the arguments of an outer PHV or aggregate here. Any
-     * SubLinks in the arguments have to be dealt with at the outer query
-     * level; they'll be handled when build_subplan collects the PHV or Aggref
-     * into the arguments to be passed down to the current subplan.
+     * Don't recurse into the arguments of an outer PHV, Aggref or
+     * GroupingFunc here.  Any SubLinks in the arguments have to be dealt with
+     * at the outer query level; they'll be handled when build_subplan
+     * collects the PHV, Aggref or GroupingFunc into the arguments to be
+     * passed down to the current subplan.
      */
     if (IsA(node, PlaceHolderVar))
     {
@@ -1972,6 +1975,11 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
         if (((Aggref *) node)->agglevelsup > 0)
             return node;
     }
+    else if (IsA(node, GroupingFunc))
+    {
+        if (((GroupingFunc *) node)->agglevelsup > 0)
+            return node;
+    }

     /*
      * We should never see a SubPlan expression in the input (since this is
@@ -2084,7 +2092,7 @@ SS_identify_outer_params(PlannerInfo *root)
     outer_params = NULL;
     for (proot = root->parent_root; proot != NULL; proot = proot->parent_root)
     {
-        /* Include ordinary Var/PHV/Aggref params */
+        /* Include ordinary Var/PHV/Aggref/GroupingFunc params */
         foreach(l, proot->plan_params)
         {
             PlannerParamItem *pitem = (PlannerParamItem *) lfirst(l);
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index b16526e65e..7f4f3f7369 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -7956,12 +7956,13 @@ get_parameter(Param *param, deparse_context *context)
         context->varprefix = true;

         /*
-         * A Param's expansion is typically a Var, Aggref, or upper-level
-         * Param, which wouldn't need extra parentheses.  Otherwise, insert
-         * parens to ensure the expression looks atomic.
+         * A Param's expansion is typically a Var, Aggref, GroupingFunc, or
+         * upper-level Param, which wouldn't need extra parentheses.
+         * Otherwise, insert parens to ensure the expression looks atomic.
          */
         need_paren = !(IsA(expr, Var) ||
                        IsA(expr, Aggref) ||
+                       IsA(expr, GroupingFunc) ||
                        IsA(expr, Param));
         if (need_paren)
             appendStringInfoChar(context->buf, '(');
@@ -8089,6 +8090,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
         case T_NextValueExpr:
         case T_NullIfExpr:
         case T_Aggref:
+        case T_GroupingFunc:
         case T_WindowFunc:
         case T_FuncExpr:
             /* function-like: name(..) or name[..] */
@@ -8205,6 +8207,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
                 case T_XmlExpr: /* own parentheses */
                 case T_NullIfExpr:    /* other separators */
                 case T_Aggref:    /* own parentheses */
+                case T_GroupingFunc:    /* own parentheses */
                 case T_WindowFunc:    /* own parentheses */
                 case T_CaseExpr:    /* other separators */
                     return true;
@@ -8255,6 +8258,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
                 case T_XmlExpr: /* own parentheses */
                 case T_NullIfExpr:    /* other separators */
                 case T_Aggref:    /* own parentheses */
+                case T_GroupingFunc:    /* own parentheses */
                 case T_WindowFunc:    /* own parentheses */
                 case T_CaseExpr:    /* other separators */
                     return true;
diff --git a/src/test/regress/expected/groupingsets.out b/src/test/regress/expected/groupingsets.out
index 58a25b691a..6a56f0b09c 100644
--- a/src/test/regress/expected/groupingsets.out
+++ b/src/test/regress/expected/groupingsets.out
@@ -2042,4 +2042,49 @@ order by a, b, c;
    |   |
 (11 rows)

+-- test handling of outer GroupingFunc within subqueries
+explain (costs off)
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by cube(v1);
+        QUERY PLAN
+---------------------------
+ MixedAggregate
+   Hash Key: $2
+   Group Key: ()
+   InitPlan 1 (returns $1)
+     ->  Result
+   InitPlan 3 (returns $2)
+     ->  Result
+   ->  Result
+   SubPlan 2
+     ->  Result
+(10 rows)
+
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by cube(v1);
+ grouping
+----------
+        1
+        0
+(2 rows)
+
+explain (costs off)
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by v1;
+        QUERY PLAN
+---------------------------
+ GroupAggregate
+   Group Key: $2
+   InitPlan 1 (returns $1)
+     ->  Result
+   InitPlan 3 (returns $2)
+     ->  Result
+   ->  Result
+   SubPlan 2
+     ->  Result
+(9 rows)
+
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by v1;
+ grouping
+----------
+        0
+(1 row)
+
 -- end
diff --git a/src/test/regress/sql/groupingsets.sql b/src/test/regress/sql/groupingsets.sql
index 473d21f6b9..8050dbf260 100644
--- a/src/test/regress/sql/groupingsets.sql
+++ b/src/test/regress/sql/groupingsets.sql
@@ -557,4 +557,13 @@ from (values (1, 2, 3), (4, null, 6), (7, 8, 9)) as t (a, b, c)
 group by rollup(a, b), rollup(a, c)
 order by a, b, c;

+-- test handling of outer GroupingFunc within subqueries
+explain (costs off)
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by cube(v1);
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by cube(v1);
+
+explain (costs off)
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by v1;
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by v1;
+
 -- end