* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/rewrite/rewriteHandler.c,v 1.148 2005/03/10 23:21:24 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/rewrite/rewriteHandler.c,v 1.149 2005/03/26 05:53:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
rewriteTargetList(Query *parsetree, Relation target_relation)
{
CmdType commandType = parsetree->commandType;
- List *tlist = parsetree->targetList;
+ TargetEntry **new_tles;
List *new_tlist = NIL;
+ List *junk_tlist = NIL;
+ Form_pg_attribute att_tup;
int attrno,
+ next_junk_attrno,
numattrs;
ListCell *temp;
/*
- * Scan the tuple description in the relation's relcache entry to make
- * sure we have all the user attributes in the right order.
+ * We process the normal (non-junk) attributes by scanning the input
+ * tlist once and transferring TLEs into an array, then scanning the
+ * array to build an output tlist. This avoids O(N^2) behavior for
+ * large numbers of attributes.
+ *
+ * Junk attributes are tossed into a separate list during the same
+ * tlist scan, then appended to the reconstructed tlist.
*/
numattrs = RelationGetNumberOfAttributes(target_relation);
+ new_tles = (TargetEntry **) palloc0(numattrs * sizeof(TargetEntry *));
+ next_junk_attrno = numattrs + 1;
- for (attrno = 1; attrno <= numattrs; attrno++)
+ foreach(temp, parsetree->targetList)
{
- Form_pg_attribute att_tup = target_relation->rd_att->attrs[attrno - 1];
- TargetEntry *new_tle = NULL;
+ TargetEntry *old_tle = (TargetEntry *) lfirst(temp);
+ Resdom *resdom = old_tle->resdom;
- /* We can ignore deleted attributes */
- if (att_tup->attisdropped)
- continue;
+ if (!resdom->resjunk)
+ {
+ /* Normal attr: stash it into new_tles[] */
+ attrno = resdom->resno;
+ if (attrno < 1 || attrno > numattrs)
+ elog(ERROR, "bogus resno %d in targetlist", attrno);
+ att_tup = target_relation->rd_att->attrs[attrno - 1];
+
+ /* We can (and must) ignore deleted attributes */
+ if (att_tup->attisdropped)
+ continue;
- /*
- * Look for targetlist entries matching this attr.
- *
- * Junk attributes are not candidates to be matched.
- */
- foreach(temp, tlist)
+ /* Merge with any prior assignment to same attribute */
+ new_tles[attrno - 1] =
+ process_matched_tle(old_tle,
+ new_tles[attrno - 1],
+ NameStr(att_tup->attname));
+ }
+ else
{
- TargetEntry *old_tle = (TargetEntry *) lfirst(temp);
- Resdom *resdom = old_tle->resdom;
+ /*
+ * Copy all resjunk tlist entries to junk_tlist, and
+ * assign them resnos above the last real resno.
+ *
+ * Typical junk entries include ORDER BY or GROUP BY expressions
+ * (are these actually possible in an INSERT or UPDATE?), system
+ * attribute references, etc.
+ */
- if (!resdom->resjunk && resdom->resno == attrno)
+ /* Get the resno right, but don't copy unnecessarily */
+ if (resdom->resno != next_junk_attrno)
{
- new_tle = process_matched_tle(old_tle, new_tle,
- NameStr(att_tup->attname));
- /* keep scanning to detect multiple assignments to attr */
+ resdom = (Resdom *) copyObject((Node *) resdom);
+ resdom->resno = next_junk_attrno;
+ old_tle = makeTargetEntry(resdom, old_tle->expr);
}
+ junk_tlist = lappend(junk_tlist, old_tle);
+ next_junk_attrno++;
}
+ }
+
+ for (attrno = 1; attrno <= numattrs; attrno++)
+ {
+ TargetEntry *new_tle = new_tles[attrno - 1];
+
+ att_tup = target_relation->rd_att->attrs[attrno - 1];
+
+ /* We can (and must) ignore deleted attributes */
+ if (att_tup->attisdropped)
+ continue;
/*
* Handle the two cases where we need to insert a default
* column, or the tlist entry is a DEFAULT placeholder node.
*/
if ((new_tle == NULL && commandType == CMD_INSERT) ||
- (new_tle && new_tle->expr && IsA(new_tle->expr, SetToDefault)))
+ (new_tle && new_tle->expr && IsA(new_tle->expr, SetToDefault)))
{
Node *new_expr;
new_tlist = lappend(new_tlist, new_tle);
}
- /*
- * Copy all resjunk tlist entries to the end of the new tlist, and
- * assign them resnos above the last real resno.
- *
- * Typical junk entries include ORDER BY or GROUP BY expressions (are
- * these actually possible in an INSERT or UPDATE?), system attribute
- * references, etc.
- */
- foreach(temp, tlist)
- {
- TargetEntry *old_tle = (TargetEntry *) lfirst(temp);
- Resdom *resdom = old_tle->resdom;
-
- if (resdom->resjunk)
- {
- /* Get the resno right, but don't copy unnecessarily */
- if (resdom->resno != attrno)
- {
- resdom = (Resdom *) copyObject((Node *) resdom);
- resdom->resno = attrno;
- old_tle = makeTargetEntry(resdom, old_tle->expr);
- }
- new_tlist = lappend(new_tlist, old_tle);
- attrno++;
- }
- else
- {
- /* Let's just make sure we processed all the non-junk items */
- if (resdom->resno < 1 || resdom->resno > numattrs)
- elog(ERROR, "bogus resno %d in targetlist", resdom->resno);
- }
- }
+ pfree(new_tles);
- parsetree->targetList = new_tlist;
+ parsetree->targetList = list_concat(new_tlist, junk_tlist);
}
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