In locate_grouping_columns(), don't expect an exact match of Var typmods.

It's possible that inlining of SQL functions (or perhaps other changes?)
has exposed typmod information not known at parse time.  In such cases,
Vars generated by query_planner might have valid typmod values while the
original grouping columns only have typmod -1.  This isn't a semantic
problem since the behavior of grouping only depends on type not typmod,
but it breaks locate_grouping_columns' use of tlist_member to locate the
matching entry in query_planner's result tlist.

We can fix this without an excessive amount of new code or complexity by
relying on the fact that locate_grouping_columns only gets called when
make_subplanTargetList has set need_tlist_eval == false, and that can only
happen if all the grouping columns are simple Vars.  Therefore we only need
to search the sub_tlist for a matching Var, and we can reasonably define a
"match" as being a match of the Var identity fields
varno/varattno/varlevelsup.  The code still Asserts that vartype matches,
but ignores vartypmod.

Per bug #8393 from Evan Martin.  The added regression test case is
basically the same as his example.  This has been broken for a very long
time, so back-patch to all supported branches.

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index f2a03a5622a73315cf7d72e0aac5fe872b2467f9..8443a82b2d8c5b136f40b8f66e4b2fc7d2a1bff3 100644 (file)
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -2508,7 +2508,8 @@ choose_hashed_distinct(PlannerInfo *root,
  * 'groupColIdx' receives an array of column numbers for the GROUP BY
  *                     expressions (if there are any) in the subplan's target list.
  * 'need_tlist_eval' is set true if we really need to evaluate the
- *                     result tlist.
+ *                     returned tlist as-is.  (Note: locate_grouping_columns assumes
+ *                     that if this is FALSE, all grouping columns are simple Vars.)
  *
  * The result is the targetlist to be passed to the subplan.
  */
@@ -2605,6 +2606,7 @@ make_subplanTargetList(PlannerInfo *root,
  * This is only needed if we don't use the sub_tlist chosen by
  * make_subplanTargetList.     We have to forget the column indexes found
  * by that routine and re-locate the grouping exprs in the real sub_tlist.
+ * We assume the grouping exprs are just Vars (see make_subplanTargetList).
  */
 static void
 locate_grouping_columns(PlannerInfo *root,
@@ -2628,11 +2630,24 @@ locate_grouping_columns(PlannerInfo *root,
        foreach(gl, root->parse->groupClause)
        {
                SortGroupClause *grpcl = (SortGroupClause *) lfirst(gl);
-               Node       *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
-               TargetEntry *te = tlist_member(groupexpr, sub_tlist);
+               Var                *groupexpr = (Var *) get_sortgroupclause_expr(grpcl, tlist);
+               TargetEntry *te;
 
+               /*
+                * The grouping column returned by create_plan might not have the same
+                * typmod as the original Var.  (This can happen in cases where a
+                * set-returning function has been inlined, so that we now have more
+                * knowledge about what it returns than we did when the original Var
+                * was created.)  So we can't use tlist_member() to search the tlist;
+                * instead use tlist_member_match_var.  For safety, still check that
+                * the vartype matches.
+                */
+               if (!(groupexpr && IsA(groupexpr, Var)))
+                       elog(ERROR, "grouping column is not a Var as expected");
+               te = tlist_member_match_var(groupexpr, sub_tlist);
                if (!te)
                        elog(ERROR, "failed to locate grouping columns");
+               Assert(((Var *) te->expr)->vartype == groupexpr->vartype);
                groupColIdx[keyno++] = te->resno;
        }
 }

diff --git a/src/backend/optimizer/util/tlist.c b/src/backend/optimizer/util/tlist.c
index 37ac8aaea22bad2fec7902bdcfe1789ff6c1dcf5..1e44f683e17c71bf7e215c77a92088874804bf26 100644 (file)
--- a/src/backend/optimizer/util/tlist.c
+++ b/src/backend/optimizer/util/tlist.c
@@ -73,6 +73,35 @@ tlist_member_ignore_relabel(Node *node, List *targetlist)
        return NULL;
 }
 
+/*
+ * tlist_member_match_var
+ *       Same as above, except that we match the provided Var on the basis
+ *       of varno/varattno/varlevelsup only, rather than using full equal().
+ *
+ * This is needed in some cases where we can't be sure of an exact typmod
+ * match.  It's probably a good idea to check the vartype anyway, but
+ * we leave it to the caller to apply any suitable sanity checks.
+ */
+TargetEntry *
+tlist_member_match_var(Var *var, List *targetlist)
+{
+       ListCell   *temp;
+
+       foreach(temp, targetlist)
+       {
+               TargetEntry *tlentry = (TargetEntry *) lfirst(temp);
+               Var                *tlvar = (Var *) tlentry->expr;
+
+               if (!tlvar || !IsA(tlvar, Var))
+                       continue;
+               if (var->varno == tlvar->varno &&
+                       var->varattno == tlvar->varattno &&
+                       var->varlevelsup == tlvar->varlevelsup)
+                       return tlentry;
+       }
+       return NULL;
+}
+
 /*
  * flatten_tlist
  *       Create a target list that only contains unique variables.

diff --git a/src/include/optimizer/tlist.h b/src/include/optimizer/tlist.h
index 22223a1c1cb05568610b8261616fbfeca3bd0b25..b84df2f61093de16519baec6596d6e34596d955a 100644 (file)
--- a/src/include/optimizer/tlist.h
+++ b/src/include/optimizer/tlist.h
@@ -19,6 +19,7 @@
 
 extern TargetEntry *tlist_member(Node *node, List *targetlist);
 extern TargetEntry *tlist_member_ignore_relabel(Node *node, List *targetlist);
+extern TargetEntry *tlist_member_match_var(Var *var, List *targetlist);
 
 extern List *flatten_tlist(List *tlist);
 extern List *add_to_flat_tlist(List *tlist, List *exprs);

diff --git a/src/test/regress/expected/rangefuncs.out b/src/test/regress/expected/rangefuncs.out
index c6a3e575afb6603eb32ec5f21e1ffb12e9b65bb5..25ba6b452331b088b8d4b5796101fe6915072110 100644 (file)
--- a/src/test/regress/expected/rangefuncs.out
+++ b/src/test/regress/expected/rangefuncs.out
@@ -574,6 +574,17 @@ SELECT * FROM foo(3);
 (9 rows)
 
 DROP FUNCTION foo(int);
+-- case that causes change of typmod knowledge during inlining
+CREATE OR REPLACE FUNCTION foo()
+RETURNS TABLE(a varchar(5))
+AS $$ SELECT 'hello'::varchar(5) $$ LANGUAGE sql STABLE;
+SELECT * FROM foo() GROUP BY 1;
+   a   
+-------
+ hello
+(1 row)
+
+DROP FUNCTION foo();
 --
 -- some tests on SQL functions with RETURNING
 --

diff --git a/src/test/regress/sql/rangefuncs.sql b/src/test/regress/sql/rangefuncs.sql
index 46aaf335d09164dba2a8791760c155cbd7330dc9..72f0ce9aff7ed58f2d3961248370a76e2096e432 100644 (file)
--- a/src/test/regress/sql/rangefuncs.sql
+++ b/src/test/regress/sql/rangefuncs.sql
@@ -286,6 +286,13 @@ AS $$ SELECT a, b
 SELECT * FROM foo(3);
 DROP FUNCTION foo(int);
 
+-- case that causes change of typmod knowledge during inlining
+CREATE OR REPLACE FUNCTION foo()
+RETURNS TABLE(a varchar(5))
+AS $$ SELECT 'hello'::varchar(5) $$ LANGUAGE sql STABLE;
+SELECT * FROM foo() GROUP BY 1;
+DROP FUNCTION foo();
+
 --
 -- some tests on SQL functions with RETURNING
 --