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Fix nested PlaceHolderVar expressions that appear only in targetlists.

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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.
This commit is contained in:
Tom Lane
2011-08-09 00:48:51 -04:00
parent d82a9d2a60
commit 77ba232564
8 changed files with 163 additions and 40 deletions
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4
src/include/optimizer/placeholder.h
View File

@@ -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);

2
src/include/optimizer/planmain.h
View File

@@ -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);