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 d0331ee8d132b2c2cabb3696c312814f75ca01ba..042c1d0676dbbedb1bb4041cd655bb907d314491 100644 (file)
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -2201,7 +2201,8 @@ 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.
  *---------------
@@ -2299,6 +2300,7 @@ 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,
@@ -2322,11 +2324,24 @@ 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 9526aefd9ac9bf36a073c01cbccdd66dd7eb6583..2f9b36e42fd3e9cf48dc5236a2afc160a0cffa16 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 1d38acaf0e43a2289979d0d3c902a7f217f84ac8..abe6680c32eaeb898223902a62f5623d327683e6 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 0769fa66f9d36fb3ed391daf96bd0d783cfb58ba..b8a6d5e40ab81dbf9b41ab972f8ed7db066596d7 100644 (file)
--- a/src/test/regress/expected/rangefuncs.out
+++ b/src/test/regress/expected/rangefuncs.out
@@ -567,6 +567,17 @@ 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 c813a3064363cce8e63c3dab1dd89c6e3ad78335..9e1fcd67b4ff2e9f9ff0e0a7654498c86ec38046 100644 (file)
--- a/src/test/regress/sql/rangefuncs.sql
+++ b/src/test/regress/sql/rangefuncs.sql
@@ -280,6 +280,13 @@ 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
 --