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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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30
src/backend/nodes/equalfuncs.c
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@@ -18,7 +18,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.295 2007/01/10 18:06:03 tgl Exp $
* $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.296 2007/01/20 20:45:38 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -596,11 +596,27 @@ _equalFromExpr(FromExpr *a, FromExpr *b)
*/
static bool
_equalPathKeyItem(PathKeyItem *a, PathKeyItem *b)
_equalPathKey(PathKey *a, PathKey *b)
{
COMPARE_NODE_FIELD(key);
COMPARE_SCALAR_FIELD(sortop);
COMPARE_SCALAR_FIELD(nulls_first);
/*
* This is normally used on non-canonicalized PathKeys, so must chase
* up to the topmost merged EquivalenceClass and see if those are the
* same (by pointer equality).
*/
EquivalenceClass *a_eclass;
EquivalenceClass *b_eclass;
a_eclass = a->pk_eclass;
while (a_eclass->ec_merged)
a_eclass = a_eclass->ec_merged;
b_eclass = b->pk_eclass;
while (b_eclass->ec_merged)
b_eclass = b_eclass->ec_merged;
if (a_eclass != b_eclass)
return false;
COMPARE_SCALAR_FIELD(pk_opfamily);
COMPARE_SCALAR_FIELD(pk_strategy);
COMPARE_SCALAR_FIELD(pk_nulls_first);
return true;
}
@@ -2016,8 +2032,8 @@ equal(void *a, void *b)
/*
* RELATION NODES
*/
case T_PathKeyItem:
retval = _equalPathKeyItem(a, b);
case T_PathKey:
retval = _equalPathKey(a, b);
break;
case T_RestrictInfo:
retval = _equalRestrictInfo(a, b);