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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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28
src/backend/utils/adt/selfuncs.c
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@ -15,7 +15,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.264 2009/12/29 20:11:45 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.265 2010/01/01 21:53:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -5614,7 +5614,7 @@ btcostestimate(PG_FUNCTION_ARGS)
int indexcol;
bool eqQualHere;
bool found_saop;
bool found_null_op;
bool found_is_null_op;
double num_sa_scans;
ListCell *l;
@ -5639,7 +5639,7 @@ btcostestimate(PG_FUNCTION_ARGS)
indexcol = 0;
eqQualHere = false;
found_saop = false;
found_null_op = false;
found_is_null_op = false;
num_sa_scans = 1;
foreach(l, indexQuals)
{
@ -5680,12 +5680,14 @@ btcostestimate(PG_FUNCTION_ARGS)
{
NullTest *nt = (NullTest *) clause;
Assert(nt->nulltesttype == IS_NULL);
leftop = (Node *) nt->arg;
rightop = NULL;
clause_op = InvalidOid;
found_null_op = true;
is_null_op = true;
if (nt->nulltesttype == IS_NULL)
{
found_is_null_op = true;
is_null_op = true;
}
}
else
{
@ -5725,12 +5727,7 @@ btcostestimate(PG_FUNCTION_ARGS)
}
}
/* check for equality operator */
if (is_null_op)
{
/* IS NULL is like = for purposes of selectivity determination */
eqQualHere = true;
}
else
if (OidIsValid(clause_op))
{
op_strategy = get_op_opfamily_strategy(clause_op,
index->opfamily[indexcol]);
@ -5738,6 +5735,11 @@ btcostestimate(PG_FUNCTION_ARGS)
if (op_strategy == BTEqualStrategyNumber)
eqQualHere = true;
}
else if (is_null_op)
{
/* IS NULL is like = for purposes of selectivity determination */
eqQualHere = true;
}
/* count up number of SA scans induced by indexBoundQuals only */
if (IsA(clause, ScalarArrayOpExpr))
{
@ -5760,7 +5762,7 @@ btcostestimate(PG_FUNCTION_ARGS)
indexcol == index->ncolumns - 1 &&
eqQualHere &&
!found_saop &&
!found_null_op)
!found_is_null_op)
numIndexTuples = 1.0;
else
{