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Use an explicit state flag to control PlaceHolderInfo creation.

Browse Source 
Up to now, callers of find_placeholder_info() were required to pass
a flag indicating if it's OK to make a new PlaceHolderInfo.  That'd
be fine if the callers had free choice, but they do not.  Once we
begin deconstruct_jointree() it's no longer OK to make more PHIs;
while callers before that always want to create a PHI if it's not
there already.  So there's no freedom of action, only the opportunity
to cause bugs by creating PHIs too late.  Let's get rid of that in
favor of adding a state flag PlannerInfo.placeholdersFrozen, which
we can set at the point where it's no longer OK to make more PHIs.

This patch also simplifies a couple of call sites that were using
complicated logic to avoid calling find_placeholder_info() as much
as possible.  Now that that lookup is O(1) thanks to the previous
commit, the extra bitmap manipulations are probably a net negative.

Discussion: https://postgr.es/m/1405792.1660677844@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2022-08-17 15:52:53 -04:00
parent 6569ca4397
commit b3ff6c742f
12 changed files with 42 additions and 49 deletions
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32
src/backend/optimizer/plan/initsplan.c
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@ -189,7 +189,7 @@ build_base_rel_tlists(PlannerInfo *root, List *final_tlist)
if (tlist_vars != NIL)
{
add_vars_to_targetlist(root, tlist_vars, bms_make_singleton(0), true);
add_vars_to_targetlist(root, tlist_vars, bms_make_singleton(0));
list_free(tlist_vars);
}
@ -206,7 +206,7 @@ build_base_rel_tlists(PlannerInfo *root, List *final_tlist)
if (having_vars != NIL)
{
add_vars_to_targetlist(root, having_vars,
bms_make_singleton(0), true);
bms_make_singleton(0));
list_free(having_vars);
}
}
@ -221,14 +221,12 @@ 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. If create_new_ph is true, it's OK
* to create new PlaceHolderInfos; otherwise, the PlaceHolderInfos must
* already exist, and we should only update their ph_needed. (This should
* be true before deconstruct_jointree begins, and false after that.)
* root->placeholder_list instead. Find or create the associated
* PlaceHolderInfo entry, and update its ph_needed.
*/
void
add_vars_to_targetlist(PlannerInfo *root, List *vars,
Relids where_needed, bool create_new_ph)
Relids where_needed)
{
ListCell *temp;
@ -262,8 +260,7 @@ add_vars_to_targetlist(PlannerInfo *root, List *vars,
else if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv,
create_new_ph);
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv);
phinfo->ph_needed = bms_add_members(phinfo->ph_needed,
where_needed);
@ -432,7 +429,7 @@ extract_lateral_references(PlannerInfo *root, RelOptInfo *brel, Index rtindex)
* Push Vars into their source relations' targetlists, and PHVs into
* root->placeholder_list.
*/
add_vars_to_targetlist(root, newvars, where_needed, true);
add_vars_to_targetlist(root, newvars, where_needed);
/* Remember the lateral references for create_lateral_join_info */
brel->lateral_vars = newvars;
@ -493,8 +490,7 @@ create_lateral_join_info(PlannerInfo *root)
else if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv,
false);
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv);
found_laterals = true;
lateral_relids = bms_add_members(lateral_relids,
@ -691,6 +687,14 @@ deconstruct_jointree(PlannerInfo *root)
Relids inner_join_rels;
List *postponed_qual_list = NIL;
/*
* After this point, no more PlaceHolderInfos may be made, because
* make_outerjoininfo and update_placeholder_eval_levels require all
* active placeholders to be present in root->placeholder_list while we
* crawl up the join tree.
*/
root->placeholdersFrozen = true;
/* Start recursion at top of jointree */
Assert(root->parse->jointree != NULL &&
IsA(root->parse->jointree, FromExpr));
@ -1866,7 +1870,7 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
PVC_RECURSE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
add_vars_to_targetlist(root, vars, relids, false);
add_vars_to_targetlist(root, vars, relids);
list_free(vars);
}
@ -2380,7 +2384,7 @@ process_implied_equality(PlannerInfo *root,
PVC_RECURSE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
add_vars_to_targetlist(root, vars, relids, false);
add_vars_to_targetlist(root, vars, relids);
list_free(vars);
}