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Teach convert_subquery_pathkeys() to handle the case where the 

subquery's pathkey is a RelabelType applied to something that appears
in the subquery's output; for example where the subquery returns a
varchar Var and the sort order is shown as that Var coerced to text.
This comes up because varchar doesn't have its own sort operator.
Per example from Peter Hardman.
This commit is contained in:
Tom Lane 2006-08-17 17:02:49 +00:00
parent 4e1bdcaabf
commit 144b0ae8ee
1 changed files with 60 additions and 26 deletions
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86
src/backend/optimizer/path/pathkeys.c
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@ -11,7 +11,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.77 2006/07/14 14:52:20 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.78 2006/08/17 17:02:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1059,39 +1059,73 @@ convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
{
PathKeyItem *sub_item = (PathKeyItem *) lfirst(j);
Node *sub_key = sub_item->key;
Expr *rtarg;
ListCell *k;
/*
* We handle two cases: the sub_pathkey key can be either an exact
* match for a targetlist entry, or a RelabelType of a targetlist
* entry. (The latter case is worth extra code because it arises
* frequently in connection with varchar fields.)
*/
if (IsA(sub_key, RelabelType))
rtarg = ((RelabelType *) sub_key)->arg;
else
rtarg = NULL;
foreach(k, sub_tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(k);
Node *outer_expr;
PathKeyItem *outer_item;
int score;
if (!tle->resjunk &&
equal(tle->expr, sub_key))
/* resjunk items aren't visible to outer query */
if (tle->resjunk)
continue;
if (equal(tle->expr, sub_key))
{
/* Found a representation for this sub_key */
Var *outer_var;
PathKeyItem *outer_item;
int score;
/* Exact match */
outer_expr = (Node *)
makeVar(rel->relid,
tle->resno,
exprType((Node *) tle->expr),
exprTypmod((Node *) tle->expr),
0);
}
else if (rtarg && equal(tle->expr, rtarg))
{
/* Match after discarding RelabelType */
outer_expr = (Node *)
makeVar(rel->relid,
tle->resno,
exprType((Node *) tle->expr),
exprTypmod((Node *) tle->expr),
0);
outer_expr = (Node *)
makeRelabelType((Expr *) outer_expr,
((RelabelType *) sub_key)->resulttype,
((RelabelType *) sub_key)->resulttypmod,
((RelabelType *) sub_key)->relabelformat);
}
else
continue;
outer_var = makeVar(rel->relid,
tle->resno,
exprType((Node *) tle->expr),
exprTypmod((Node *) tle->expr),
0);
outer_item = makePathKeyItem((Node *) outer_var,
sub_item->sortop,
true);
/* score = # of mergejoin peers */
score = count_canonical_peers(root, outer_item);
/* +1 if it matches the proper query_pathkeys item */
if (retvallen < outer_query_keys &&
list_member(list_nth(root->query_pathkeys, retvallen), outer_item))
score++;
if (score > best_score)
{
best_item = outer_item;
best_score = score;
}
/* Found a representation for this sub_key */
outer_item = makePathKeyItem(outer_expr,
sub_item->sortop,
true);
/* score = # of mergejoin peers */
score = count_canonical_peers(root, outer_item);
/* +1 if it matches the proper query_pathkeys item */
if (retvallen < outer_query_keys &&
list_member(list_nth(root->query_pathkeys, retvallen), outer_item))
score++;
if (score > best_score)
{
best_item = outer_item;
best_score = score;
}
}
}