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Refactor planner's pathkeys data structure to create a separate, explicit

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representation of equivalence classes of variables.  This is an extensive
rewrite, but it brings a number of benefits:
* planner no longer fails in the presence of "incomplete" operator families
that don't offer operators for every possible combination of datatypes.
* avoid generating and then discarding redundant equality clauses.
* remove bogus assumption that derived equalities always use operators
named "=".
* mergejoins can work with a variety of sort orders (e.g., descending) now,
instead of tying each mergejoinable operator to exactly one sort order.
* better recognition of redundant sort columns.
* can make use of equalities appearing underneath an outer join.
This commit is contained in:
Tom Lane
2007-01-20 20:45:41 +00:00
parent 2b7334d487
commit f41803bb39
35 changed files with 3882 additions and 2719 deletions
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23
src/backend/nodes/print.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/nodes/print.c,v 1.82 2007/01/05 22:19:30 momjian Exp $
* $PostgreSQL: pgsql/src/backend/nodes/print.c,v 1.83 2007/01/20 20:45:38 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@ -404,7 +404,7 @@ print_expr(Node *expr, List *rtable)
/*
* print_pathkeys -
* pathkeys list of list of PathKeyItems
* pathkeys list of PathKeys
*/
void
print_pathkeys(List *pathkeys, List *rtable)
@ -414,17 +414,26 @@ print_pathkeys(List *pathkeys, List *rtable)
printf("(");
foreach(i, pathkeys)
{
List *pathkey = (List *) lfirst(i);
PathKey *pathkey = (PathKey *) lfirst(i);
EquivalenceClass *eclass;
ListCell *k;
bool first = true;
eclass = pathkey->pk_eclass;
/* chase up, in case pathkey is non-canonical */
while (eclass->ec_merged)
eclass = eclass->ec_merged;
printf("(");
foreach(k, pathkey)
foreach(k, eclass->ec_members)
{
PathKeyItem *item = (PathKeyItem *) lfirst(k);
EquivalenceMember *mem = (EquivalenceMember *) lfirst(k);
print_expr(item->key, rtable);
if (lnext(k))
if (first)
first = false;
else
printf(", ");
print_expr((Node *) mem->em_expr, rtable);
}
printf(")");
if (lnext(i))