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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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6
src/backend/access/common/scankey.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/common/scankey.c,v 1.32 2009/01/01 17:23:34 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/common/scankey.c,v 1.33 2010/01/01 21:53:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -21,7 +21,7 @@
* ScanKeyEntryInitialize
* Initializes a scan key entry given all the field values.
* The target procedure is specified by OID (but can be invalid
* if SK_SEARCHNULL is set).
* if SK_SEARCHNULL or SK_SEARCHNOTNULL is set).
*
* Note: CurrentMemoryContext at call should be as long-lived as the ScanKey
* itself, because that's what will be used for any subsidiary info attached
@ -45,7 +45,7 @@ ScanKeyEntryInitialize(ScanKey entry,
fmgr_info(procedure, &entry->sk_func);
else
{
Assert(flags & SK_SEARCHNULL);
Assert(flags & (SK_SEARCHNULL | SK_SEARCHNOTNULL));
MemSet(&entry->sk_func, 0, sizeof(entry->sk_func));
}
}