Fix an old thinko in SS_make_initplan_from_plan, which is used when optimizing

a MIN or MAX aggregate call into an indexscan: the initplan is being made at
the current query nesting level and so we shouldn't increment query_level.
Though usually harmless, this mistake could lead to bogus "plan should not
reference subplan's variable" failures on complex queries.  Per bug report
from David Sanchez i Gregori.

src/backend/optimizer/plan/subselect.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.122 2007/02/27 01:11:25 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.123 2007/07/18 21:40:57 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1328,11 +1328,14 @@ SS_make_initplan_from_plan(PlannerInfo *root, Plan *plan,
 	Param	   *prm;
 
 	/*
-	 * Set up for a new level of subquery.	This is just to keep
-	 * SS_finalize_plan from becoming confused; we don't bother with making
-	 * a whole new PlannerInfo struct.
+	 * We must run SS_finalize_plan(), since that's normally done before a
+	 * subplan gets put into the initplan list.  However it will try to attach
+	 * any pre-existing initplans to this one, which we don't want (they are
+	 * siblings not children of this initplan).  So, a quick kluge to hide
+	 * them.  (This is something else that could perhaps be cleaner if we did
+	 * extParam/allParam processing in setrefs.c instead of here?  See notes
+	 * for materialize_finished_plan.)
 	 */
-	root->query_level++;
 	saved_init_plans = root->init_plans;
 	root->init_plans = NIL;
 
@@ -1341,8 +1344,7 @@ SS_make_initplan_from_plan(PlannerInfo *root, Plan *plan,
 	 */
 	SS_finalize_plan(root, plan);
 
-	/* Return to outer subquery context */
-	root->query_level--;
+	/* Restore outer initplan list */
 	root->init_plans = saved_init_plans;
 
 	/*

src/test/regress/expected/subselect.out

@@ -386,3 +386,25 @@ select f1, ss1 as relabel from
  -2147483647 |          0
 (5 rows)
 
+--
+-- Test cases involving PARAM_EXEC parameters and min/max index optimizations.
+-- Per bug report from David Sanchez i Gregori.
+--
+select * from (
+  select max(unique1) from tenk1 as a
+  where exists (select 1 from tenk1 as b where b.thousand = a.unique2)
+) ss;
+ max  
+------
+ 9997
+(1 row)
+
+select * from (
+  select min(unique1) from tenk1 as a
+  where not exists (select 1 from tenk1 as b where b.unique2 = 10000)
+) ss;
+ min 
+-----
+   0
+(1 row)
+

src/test/regress/sql/subselect.sql

@@ -236,3 +236,18 @@ select * from shipped_view;
 select f1, ss1 as relabel from
     (select *, (select sum(f1) from int4_tbl b where f1 >= a.f1) as ss1
      from int4_tbl a) ss;
+
+--
+-- Test cases involving PARAM_EXEC parameters and min/max index optimizations.
+-- Per bug report from David Sanchez i Gregori.
+--
+
+select * from (
+  select max(unique1) from tenk1 as a
+  where exists (select 1 from tenk1 as b where b.thousand = a.unique2)
+) ss;
+
+select * from (
+  select min(unique1) from tenk1 as a
+  where not exists (select 1 from tenk1 as b where b.unique2 = 10000)
+) ss;