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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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29
src/backend/executor/nodeIndexscan.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.136 2009/10/26 02:26:31 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.137 2010/01/01 21:53:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -640,7 +640,8 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
* (Note that we treat all array-expressions as requiring runtime evaluation,
* even if they happen to be constants.)
*
* 5. NullTest ("indexkey IS NULL"). We just fill in the ScanKey properly.
* 5. NullTest ("indexkey IS NULL/IS NOT NULL"). We just fill in the
* ScanKey properly.
*
* Input params are:
*
@ -987,13 +988,14 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
}
else if (IsA(clause, NullTest))
{
/* indexkey IS NULL */
Assert(((NullTest *) clause)->nulltesttype == IS_NULL);
/* indexkey IS NULL or indexkey IS NOT NULL */
NullTest *ntest = (NullTest *) clause;
int flags;
/*
* argument should be the index key Var, possibly relabeled
*/
leftop = ((NullTest *) clause)->arg;
leftop = ntest->arg;
if (leftop && IsA(leftop, RelabelType))
leftop = ((RelabelType *) leftop)->arg;
@ -1009,8 +1011,23 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
/*
* initialize the scan key's fields appropriately
*/
switch (ntest->nulltesttype)
{
case IS_NULL:
flags = SK_ISNULL | SK_SEARCHNULL;
break;
case IS_NOT_NULL:
flags = SK_ISNULL | SK_SEARCHNOTNULL;
break;
default:
elog(ERROR, "unrecognized nulltesttype: %d",
(int) ntest->nulltesttype);
flags = 0; /* keep compiler quiet */
break;
}
ScanKeyEntryInitialize(this_scan_key,
SK_ISNULL | SK_SEARCHNULL,
flags,
varattno, /* attribute number to scan */
InvalidStrategy, /* no strategy */
InvalidOid, /* no strategy subtype */