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Make 'col IS NULL' clauses be indexable conditions.

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Teodor Sigaev, with some kibitzing from Tom Lane.
This commit is contained in:
Tom Lane
2007-04-06 22:33:43 +00:00
parent 146c83c045
commit f02a82b6ad
19 changed files with 432 additions and 110 deletions
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93
src/backend/access/nbtree/nbtutils.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.83 2007/03/30 00:12:59 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.84 2007/04/06 22:33:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -264,12 +264,27 @@ _bt_preprocess_keys(IndexScanDesc scan)
if (numberOfKeys == 1)
{
/*
* We don't use indices for 'A is null' and 'A is not null' currently
* and 'A < = > <> NULL' will always fail - so qual is not OK if
* comparison value is NULL. - vadim 03/21/97
* We treat all btree operators as strict (even if they're not so
* marked in pg_proc). This means that it is impossible for an
* operator condition with a NULL comparison constant to succeed,
* and we can reject it right away.
*
* However, we now also support "x IS NULL" clauses as search
* conditions, so in that case keep going. The planner has not
* filled in any particular strategy in this case, so set it to
* BTEqualStrategyNumber --- we can treat IS NULL as an equality
* operator for purposes of search strategy.
*/
if (cur->sk_flags & SK_ISNULL)
so->qual_ok = false;
{
if (cur->sk_flags & SK_SEARCHNULL)
{
cur->sk_strategy = BTEqualStrategyNumber;
cur->sk_subtype = InvalidOid;
}
else
so->qual_ok = false;
}
_bt_mark_scankey_with_indoption(cur, indoption);
memcpy(outkeys, cur, sizeof(ScanKeyData));
so->numberOfKeys = 1;
@ -303,17 +318,20 @@ _bt_preprocess_keys(IndexScanDesc scan)
{
if (i < numberOfKeys)
{
/* See comments above: any NULL implies cannot match qual */
/* See comments above about NULLs and IS NULL handling. */
/* Note: we assume SK_ISNULL is never set in a row header key */
if (cur->sk_flags & SK_ISNULL)
{
so->qual_ok = false;
/*
* Quit processing so we don't try to invoke comparison
* routines on NULLs.
*/
return;
if (cur->sk_flags & SK_SEARCHNULL)
{
cur->sk_strategy = BTEqualStrategyNumber;
cur->sk_subtype = InvalidOid;
}
else
{
so->qual_ok = false;
return;
}
}
}
@ -344,6 +362,14 @@ _bt_preprocess_keys(IndexScanDesc scan)
if (!chk || j == (BTEqualStrategyNumber - 1))
continue;
/* IS NULL together with any other predicate must fail */
if (eq->sk_flags & SK_SEARCHNULL)
{
so->qual_ok = false;
return;
}
if (_bt_compare_scankey_args(scan, chk, eq, chk,
&test_result))
{
@ -455,6 +481,23 @@ _bt_preprocess_keys(IndexScanDesc scan)
else
{
/* yup, keep only the more restrictive key */
/* if either arg is NULL, don't try to compare */
if ((cur->sk_flags | xform[j]->sk_flags) & SK_ISNULL)
{
/* at least one of them must be an IS NULL clause */
Assert(j == (BTEqualStrategyNumber - 1));
Assert((cur->sk_flags | xform[j]->sk_flags) & SK_SEARCHNULL);
/* if one is and one isn't, the search must fail */
if ((cur->sk_flags ^ xform[j]->sk_flags) & SK_SEARCHNULL)
{
so->qual_ok = false;
return;
}
/* we have duplicate IS NULL clauses, ignore the newer one */
continue;
}
if (_bt_compare_scankey_args(scan, cur, cur, xform[j],
&test_result))
{
@ -798,11 +841,29 @@ _bt_checkkeys(IndexScanDesc scan,
tupdesc,
&isNull);
/* btree doesn't support 'A is null' clauses, yet */
if (key->sk_flags & SK_ISNULL)
{
/* we shouldn't get here, really; see _bt_preprocess_keys() */
*continuescan = false;
/* Handle IS NULL tests */
Assert(key->sk_flags & SK_SEARCHNULL);
if (isNull)
continue; /* tuple satisfies this qual */
/*
* Tuple fails this qual. If it's a required qual for the current
* scan direction, then we can conclude no further tuples will
* pass, either.
*/
if ((key->sk_flags & SK_BT_REQFWD) &&
ScanDirectionIsForward(dir))
*continuescan = false;
else if ((key->sk_flags & SK_BT_REQBKWD) &&
ScanDirectionIsBackward(dir))
*continuescan = false;
/*
* In any case, this indextuple doesn't match the qual.
*/
return false;
}