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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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27
src/backend/optimizer/plan/initsplan.c
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@@ -137,7 +137,7 @@ build_base_rel_tlists(PlannerInfo *root, List *final_tlist)
if (tlist_vars != NIL)
{
add_vars_to_targetlist(root, tlist_vars, bms_make_singleton(0));
add_vars_to_targetlist(root, tlist_vars, bms_make_singleton(0), true);
list_free(tlist_vars);
}
}
@@ -151,10 +151,15 @@ build_base_rel_tlists(PlannerInfo *root, List *final_tlist)
*
* The list may also contain PlaceHolderVars. These don't necessarily
* have a single owning relation; we keep their attr_needed info in
* root->placeholder_list instead.
* root->placeholder_list instead. If create_new_ph is true, it's OK
* to create new PlaceHolderInfos, and we also have to update ph_may_need;
* otherwise, the PlaceHolderInfos must already exist, and we should only
* update their ph_needed. (It should be true before deconstruct_jointree
* begins, and false after that.)
*/
void
add_vars_to_targetlist(PlannerInfo *root, List *vars, Relids where_needed)
add_vars_to_targetlist(PlannerInfo *root, List *vars,
Relids where_needed, bool create_new_ph)
{
ListCell *temp;
@@ -185,18 +190,20 @@ add_vars_to_targetlist(PlannerInfo *root, List *vars, Relids where_needed)
else if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv);
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv,
create_new_ph);
/* Always adjust ph_needed */
phinfo->ph_needed = bms_add_members(phinfo->ph_needed,
where_needed);
/*
* Update ph_may_need too. This is currently only necessary when
* being called from build_base_rel_tlists, but we may as well do
* it always.
* If we are creating PlaceHolderInfos, mark them with the
* correct maybe-needed locations. Otherwise, it's too late to
* change that.
*/
phinfo->ph_may_need = bms_add_members(phinfo->ph_may_need,
where_needed);
if (create_new_ph)
mark_placeholder_maybe_needed(root, phinfo, where_needed);
}
else
elog(ERROR, "unrecognized node type: %d", (int) nodeTag(node));
@@ -1035,7 +1042,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
PVC_RECURSE_AGGREGATES,
PVC_INCLUDE_PLACEHOLDERS);
add_vars_to_targetlist(root, vars, relids);
add_vars_to_targetlist(root, vars, relids, false);
list_free(vars);
}