Assign sort keys properly when there are duplicate entries in
pathkey list --- corrects misbehavior seen with multiple mergejoin clauses mentioning same variable.
This commit is contained in:
Tom Lane
parent
55179388f9
commit
91f82de48a
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@ -7,7 +7,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.71 1999/08/16 02:17:53 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.72 1999/08/16 23:07:20 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -28,7 +28,7 @@
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static List *switch_outer(List *clauses);
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static List *set_tlist_sort_info(List *tlist, List *pathkeys);
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static int set_tlist_sort_info(List *tlist, List *pathkeys);
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static Scan *create_scan_node(Path *best_path, List *tlist);
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static Join *create_join_node(JoinPath *best_path, List *tlist);
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static SeqScan *create_seqscan_node(Path *best_path, List *tlist,
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@ -804,40 +804,65 @@ switch_outer(List *clauses)
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* Sets the reskey and reskeyop fields of resdom nodes in a target list
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* for a sort node.
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*
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* 'tlist' is the target list
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* 'tlist' is the target list (which is modified in-place).
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* tlist's reskey fields must be clear to start with.
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* 'pathkeys' is the desired pathkeys for the sort. NIL means no sort.
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*
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* Returns the modified-in-place target list.
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* Returns the number of sort keys assigned (which might be less than
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* length(pathkeys)!)
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*/
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static List *
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static int
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set_tlist_sort_info(List *tlist, List *pathkeys)
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{
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int keyno = 1;
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int keysassigned = 0;
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List *i;
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foreach(i, pathkeys)
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{
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List *keysublist = (List *) lfirst(i);
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PathKeyItem *pathkey;
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Resdom *resdom;
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PathKeyItem *pathkey = NULL;
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Resdom *resdom = NULL;
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List *j;
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/*
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* We can sort by any one of the sort key items listed in this
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* sublist. For now, we always take the first one --- is there
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* any way of figuring out which might be cheapest to execute?
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* (For example, int4lt is likely much cheaper to execute than
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* numericlt, but both might appear in the same pathkey sublist...)
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* sublist. For now, we take the first one that corresponds to
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* an available Var in the tlist.
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*
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* XXX if we have a choice, is there any way of figuring out which
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* might be cheapest to execute? (For example, int4lt is likely
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* much cheaper to execute than numericlt, but both might appear in
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* the same pathkey sublist...) Not clear that we ever will have
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* a choice in practice, so it may not matter.
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*/
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pathkey = lfirst(keysublist);
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Assert(IsA(pathkey, PathKeyItem));
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resdom = tlist_member((Var *) pathkey->key, tlist);
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foreach(j, keysublist)
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{
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pathkey = lfirst(j);
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Assert(IsA(pathkey, PathKeyItem));
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resdom = tlist_member((Var *) pathkey->key, tlist);
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if (resdom)
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break;
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}
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if (!resdom)
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elog(ERROR, "set_tlist_sort_info: cannot find tlist item to sort");
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resdom->reskey = keyno;
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resdom->reskeyop = get_opcode(pathkey->sortop);
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keyno++;
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/*
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* The resdom might be already marked as a sort key, if the pathkeys
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* contain duplicate entries. (This can happen in scenarios where
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* multiple mergejoinable clauses mention the same var, for example.)
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* In that case the current pathkey is essentially a no-op, because
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* only one value can be seen within any subgroup where it would be
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* consulted. We can ignore it.
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*/
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if (resdom->reskey == 0)
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{
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/* OK, mark it as a sort key and set the sort operator regproc */
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resdom->reskey = ++keysassigned;
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resdom->reskeyop = get_opcode(pathkey->sortop);
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}
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}
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return tlist;
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return keysassigned;
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}
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/*
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@ -885,34 +910,37 @@ make_noname(List *tlist,
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Plan *plan_node)
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{
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List *noname_tlist;
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int numsortkeys;
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Plan *tmpplan;
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Noname *retval;
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/* Create a new target list for the noname, with sort keys set. */
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noname_tlist = set_tlist_sort_info(new_unsorted_tlist(tlist),
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pathkeys);
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noname_tlist = new_unsorted_tlist(tlist);
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numsortkeys = set_tlist_sort_info(noname_tlist, pathkeys);
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if (pathkeys != NIL)
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if (numsortkeys > 0)
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{
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/* need to sort */
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retval = (Noname *) make_seqscan(tlist,
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NIL,
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_NONAME_RELATION_ID_,
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(Plan *) make_sort(noname_tlist,
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_NONAME_RELATION_ID_,
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plan_node,
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length(pathkeys)));
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tmpplan = (Plan *) make_sort(noname_tlist,
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_NONAME_RELATION_ID_,
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plan_node,
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numsortkeys);
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}
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else
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{
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/* no sort */
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retval = (Noname *) make_seqscan(tlist,
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NIL,
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tmpplan = (Plan *) make_material(noname_tlist,
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_NONAME_RELATION_ID_,
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(Plan *) make_material(noname_tlist,
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_NONAME_RELATION_ID_,
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plan_node,
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0));
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plan_node,
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0);
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}
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/* Return a seqscan using the original tlist */
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retval = (Noname *) make_seqscan(tlist,
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NIL,
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_NONAME_RELATION_ID_,
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tmpplan);
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return retval;
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}
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