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Fix oversight in handling of row-comparison index keys: if the row comparison

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doesn't exactly match the index, we may have to change our initial positioning
strategy.  For example, given an index on (f1,f2,f3) and a WHERE condition
"ROW(f1,f3) > ROW(2,3)", the code extracted the initial-positioning condition
"f1 > 2", which is wrong ... it has to be "f1 >= 2", else some rows matching
the WHERE condition may fail to be returned.

Applying patch to 8.2 only --- I'll fix it in HEAD later as part of the
planned index improvements (reverse-sort and NULLS FIRST/LAST work).
This commit is contained in:
Tom Lane 2007-01-07 01:56:24 +00:00
parent 79a0a57581
commit 2054724c08
1 changed files with 38 additions and 12 deletions
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50
src/backend/access/nbtree/nbtsearch.c
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@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.107 2006/10/04 00:29:49 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.107.2.1 2007/01/07 01:56:24 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -617,11 +617,12 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
* in the first row member makes the condition unmatchable, just
* like qual_ok = false.
*/
cur = (ScanKey) DatumGetPointer(cur->sk_argument);
Assert(cur->sk_flags & SK_ROW_MEMBER);
if (cur->sk_flags & SK_ISNULL)
ScanKey subkey = (ScanKey) DatumGetPointer(cur->sk_argument);
Assert(subkey->sk_flags & SK_ROW_MEMBER);
if (subkey->sk_flags & SK_ISNULL)
return false;
memcpy(scankeys + i, cur, sizeof(ScanKeyData));
memcpy(scankeys + i, subkey, sizeof(ScanKeyData));
/*
* If the row comparison is the last positioning key we accepted,
@ -632,21 +633,46 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
* even if the row comparison is of ">" or "<" type, because the
* condition applied to all but the last row member is effectively
* ">=" or "<=", and so the extra keys don't break the positioning
* scheme.
* scheme. But, by the same token, if we aren't able to use all
* the row members, then the part of the row comparison that we
* did use has to be treated as just a ">=" or "<=" condition,
* and so we'd better adjust strat_total accordingly.
*/
if (i == keysCount - 1)
{
while (!(cur->sk_flags & SK_ROW_END))
bool used_all_subkeys = false;
Assert(!(subkey->sk_flags & SK_ROW_END));
for(;;)
{
cur++;
Assert(cur->sk_flags & SK_ROW_MEMBER);
if (cur->sk_attno != keysCount + 1)
subkey++;
Assert(subkey->sk_flags & SK_ROW_MEMBER);
if (subkey->sk_attno != keysCount + 1)
break; /* out-of-sequence, can't use it */
if (cur->sk_flags & SK_ISNULL)
if (subkey->sk_strategy != cur->sk_strategy)
break; /* wrong direction, can't use it */
if (subkey->sk_flags & SK_ISNULL)
break; /* can't use null keys */
Assert(keysCount < INDEX_MAX_KEYS);
memcpy(scankeys + keysCount, cur, sizeof(ScanKeyData));
memcpy(scankeys + keysCount, subkey, sizeof(ScanKeyData));
keysCount++;
if (subkey->sk_flags & SK_ROW_END)
{
used_all_subkeys = true;
break;
}
}
if (!used_all_subkeys)
{
switch (strat_total)
{
case BTLessStrategyNumber:
strat_total = BTLessEqualStrategyNumber;
break;
case BTGreaterStrategyNumber:
strat_total = BTGreaterEqualStrategyNumber;
break;
}
}
break; /* done with outer loop */
}