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

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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
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22
src/backend/access/gist/gistget.c
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@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.82 2009/10/08 22:34:57 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.83 2010/01/01 21:53:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -413,14 +413,20 @@ gistindex_keytest(IndexTuple tuple,
{
/*
* On non-leaf page we can't conclude that child hasn't NULL
* values because of assumption in GiST: uinon (VAL, NULL) is VAL
* But if on non-leaf page key IS NULL then all childs has NULL.
* values because of assumption in GiST: union (VAL, NULL) is VAL.
* But if on non-leaf page key IS NULL, then all children are NULL.
*/
Assert(key->sk_flags & SK_SEARCHNULL);
if (GistPageIsLeaf(p) && !isNull)
return false;
if (key->sk_flags & SK_SEARCHNULL)
{
if (GistPageIsLeaf(p) && !isNull)
return false;
}
else
{
Assert(key->sk_flags & SK_SEARCHNOTNULL);
if (isNull)
return false;
}
}
else if (isNull)
{