From 77ba23256404d6f975a80d5402e62f6047c67b3a Mon Sep 17 00:00:00 2001
From: Tom Lane
Date: Tue, 9 Aug 2011 00:48:51 -0400
Subject: Fix nested PlaceHolderVar expressions that appear only in
 targetlists.

A PlaceHolderVar's expression might contain another, lower-level
PlaceHolderVar.  If the outer PlaceHolderVar is used, the inner one
certainly will be also, and so we have to make sure that both of them get
into the placeholder_list with correct ph_may_need values during the
initial pre-scan of the query (before deconstruct_jointree starts).
We did this correctly for PlaceHolderVars appearing in the query quals,
but overlooked the issue for those appearing in the top-level targetlist;
with the result that nested placeholders referenced only in the targetlist
did not work correctly, as illustrated in bug #6154.

While at it, add some error checking to find_placeholder_info to ensure
that we don't try to create new placeholders after it's too late to do so;
they have to all be created before deconstruct_jointree starts.

Back-patch to 8.4 where the PlaceHolderVar mechanism was introduced.
---
 src/include/optimizer/placeholder.h | 4 +++-
 src/include/optimizer/planmain.h    | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

(limited to 'src/include')

diff --git a/src/include/optimizer/placeholder.h b/src/include/optimizer/placeholder.h
index cce9e1ef1b..f112419fd5 100644
--- a/src/include/optimizer/placeholder.h
+++ b/src/include/optimizer/placeholder.h
@@ -20,8 +20,10 @@
 extern PlaceHolderVar *make_placeholder_expr(PlannerInfo *root, Expr *expr,
 					  Relids phrels);
 extern PlaceHolderInfo *find_placeholder_info(PlannerInfo *root,
-					  PlaceHolderVar *phv);
+					  PlaceHolderVar *phv, bool create_new_ph);
 extern void find_placeholders_in_jointree(PlannerInfo *root);
+extern void mark_placeholder_maybe_needed(PlannerInfo *root,
+							  PlaceHolderInfo *phinfo, Relids relids);
 extern void update_placeholder_eval_levels(PlannerInfo *root,
 							   SpecialJoinInfo *new_sjinfo);
 extern void fix_placeholder_input_needed_levels(PlannerInfo *root);
diff --git a/src/include/optimizer/planmain.h b/src/include/optimizer/planmain.h
index 5261691af6..69ba6b6923 100644
--- a/src/include/optimizer/planmain.h
+++ b/src/include/optimizer/planmain.h
@@ -92,7 +92,7 @@ extern int	join_collapse_limit;
 extern void add_base_rels_to_query(PlannerInfo *root, Node *jtnode);
 extern void build_base_rel_tlists(PlannerInfo *root, List *final_tlist);
 extern void add_vars_to_targetlist(PlannerInfo *root, List *vars,
-					   Relids where_needed);
+					   Relids where_needed, bool create_new_ph);
 extern List *deconstruct_jointree(PlannerInfo *root);
 extern void distribute_restrictinfo_to_rels(PlannerInfo *root,
 								RestrictInfo *restrictinfo);
-- 
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