* 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 $
*
*-------------------------------------------------------------------------
*/
{
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;
-
- 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;
- }
+ /* 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;
+
+ /* 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;
}
}
}