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 a49b516141e8f50bbdb8f44b5d109c15db1c19aa..432ea3106b13d166d5f5dc946928ab61a6f459f2 100644 (file)
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -2809,7 +2809,8 @@ choose_hashed_distinct(PlannerInfo *root,
  * 'groupColIdx' receives an array of column numbers for the GROUP BY
  *                     expressions (if there are any) in the returned target list.
  * 'need_tlist_eval' is set true if we really need to evaluate the
- *                     returned tlist as-is.
+ *                     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 query_planner.
  */
@@ -2972,6 +2973,7 @@ get_grouping_column_index(Query *parse, TargetEntry *tle)
  * 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,
@@ -2995,11 +2997,24 @@ 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 5dc4b835fa3d6588b17e007cbc7cf3a1b0b41479..5cc3cdc15a6638c93e2a22b14c4d3ad979e1aa45 100644 (file)
--- a/src/backend/optimizer/util/tlist.c
+++ b/src/backend/optimizer/util/tlist.c
@@ -71,6 +71,35 @@ 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 0d6f05199ae0e37786d7ac022aeb5fa77ab05b77..ad01f2e4856517b853dfb8c2b8c5402baf5fe8cc 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, PVCAggregateBehavior aggbehavior,
                          PVCPlaceHolderBehavior phbehavior);

diff --git a/src/test/regress/expected/rangefuncs.out b/src/test/regress/expected/rangefuncs.out
index 16782776f45222b9b9ad75c5c776993baf5554dc..b71cb8420ee4af589fab688fa2477330fd2cfe5c 100644 (file)
--- a/src/test/regress/expected/rangefuncs.out
+++ b/src/test/regress/expected/rangefuncs.out
@@ -576,6 +576,17 @@ 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 f1a405a5f7eb5716d66dd815b0908d8e3accc95a..462c6663f209591f809c4ba4ee7f661b505016ed 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
 --