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Support "x IS NOT NULL" clauses as indexscan conditions. This turns out

to be just a minor extension of the previous patch that made "x IS NULL"
indexable, because we can treat the IS NOT NULL condition as if it were
"x < NULL" or "x > NULL" (depending on the index's NULLS FIRST/LAST option),
just like IS NULL is treated like "x = NULL".  Aside from any possible
usefulness in its own right, this is an important improvement for
index-optimized MAX/MIN aggregates: it is now reliably possible to get
a column's min or max value cheaply, even when there are a lot of nulls
cluttering the interesting end of the index.
This commit is contained in:
Tom Lane
2010-01-01 21:53:49 +00:00
parent 15faca2596
commit 29c4ad9829
18 changed files with 295 additions and 120 deletions

View File

@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.242 2009/09/17 20:49:28 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.243 2010/01/01 21:53:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1218,7 +1218,7 @@ match_clause_to_indexcol(IndexOptInfo *index,
* Clause must be a binary opclause, or possibly a ScalarArrayOpExpr
* (which is always binary, by definition). Or it could be a
* RowCompareExpr, which we pass off to match_rowcompare_to_indexcol().
* Or, if the index supports it, we can handle IS NULL clauses.
* Or, if the index supports it, we can handle IS NULL/NOT NULL clauses.
*/
if (is_opclause(clause))
{
@ -1256,8 +1256,7 @@ match_clause_to_indexcol(IndexOptInfo *index,
{
NullTest *nt = (NullTest *) clause;
if (nt->nulltesttype == IS_NULL &&
match_index_to_operand((Node *) nt->arg, indexcol, index))
if (match_index_to_operand((Node *) nt->arg, indexcol, index))
return true;
return false;
}