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Change the planner to allow indexscan qualification clauses to use

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nonconsecutive columns of a multicolumn index, as per discussion around
mid-May (pghackers thread "Best way to scan on-disk bitmaps").  This
turns out to require only minimal changes in btree, and so far as I can
see none at all in GiST.  btcostestimate did need some work, but its
original assumption that index selectivity == heap selectivity was
quite bogus even before this.
This commit is contained in:
Tom Lane
2005-06-13 23:14:49 +00:00
parent 077811605e
commit c186c93148
12 changed files with 208 additions and 114 deletions
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17
src/backend/access/nbtree/nbtutils.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.62 2004/12/31 21:59:22 pgsql Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.63 2005/06/13 23:14:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -190,7 +190,9 @@ _bt_formitem(IndexTuple itup)
* matched to continue the scan. In general, numberOfRequiredKeys is equal
* to the number of keys for leading attributes with "=" keys, plus the
* key(s) for the first non "=" attribute, which can be seen to be correct
* by considering the above example.
* by considering the above example. Note in particular that if there are no
* keys for a given attribute, the keys for subsequent attributes can never
* be required; for instance "WHERE y = 4" requires a full-index scan.
*
* If possible, redundant keys are eliminated: we keep only the tightest
* >/>= bound and the tightest </<= bound, and if there's an = key then
@ -248,8 +250,8 @@ _bt_preprocess_keys(IndexScanDesc scan)
outkeys = so->keyData;
cur = &inkeys[0];
/* we check that input keys are correctly ordered */
if (cur->sk_attno != 1)
elog(ERROR, "key(s) for attribute 1 missed");
if (cur->sk_attno < 1)
elog(ERROR, "btree index keys must be ordered by attribute");
/* We can short-circuit most of the work if there's just one key */
if (numberOfKeys == 1)
@ -270,7 +272,8 @@ _bt_preprocess_keys(IndexScanDesc scan)
}
memcpy(outkeys, inkeys, sizeof(ScanKeyData));
so->numberOfKeys = 1;
so->numberOfRequiredKeys = 1;
if (cur->sk_attno == 1)
so->numberOfRequiredKeys = 1;
return;
}
@ -324,8 +327,8 @@ _bt_preprocess_keys(IndexScanDesc scan)
int priorNumberOfEqualCols = numberOfEqualCols;
/* check input keys are correctly ordered */
if (i < numberOfKeys && cur->sk_attno != attno + 1)
elog(ERROR, "key(s) for attribute %d missed", attno + 1);
if (i < numberOfKeys && cur->sk_attno < attno)
elog(ERROR, "btree index keys must be ordered by attribute");
/*
* If = has been specified, no other key will be used. In case