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Commit5b76bb1

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Dept of second thoughts: my first cut at supporting "x IS NOT NULL" btree
indexscans would do the wrong thing if index_rescan() was called with aNULL instead of a new set of scankeys and the index was DESC order,because sk_strategy would not get flipped a second time. I thinkthat those provisions for a NULL argument are dead code now as far as thecore backend goes, but possibly somebody somewhere is still using it.In any case, this refactoring seems clearer, and it's definitely shorter.
1 parentc3705d8 commit5b76bb1

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1 file changed

+75
-80
lines changed

1 file changed

+75
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lines changed

‎src/backend/access/nbtree/nbtutils.c

Lines changed: 75 additions & 80 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.96 2010/01/02 16:57:35 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtutils.c,v 1.97 2010/01/03 05:39:08 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -32,7 +32,7 @@
3232
staticbool_bt_compare_scankey_args(IndexScanDescscan,ScanKeyop,
3333
ScanKeyleftarg,ScanKeyrightarg,
3434
bool*result);
35-
staticvoid_bt_mark_scankey_with_indoption(ScanKeyskey,int16*indoption);
35+
staticbool_bt_fix_scankey_strategy(ScanKeyskey,int16*indoption);
3636
staticvoid_bt_mark_scankey_required(ScanKeyskey);
3737
staticbool_bt_check_rowcompare(ScanKeyskey,
3838
IndexTupletuple,TupleDesctupdesc,
@@ -265,49 +265,9 @@ _bt_preprocess_keys(IndexScanDesc scan)
265265
/* We can short-circuit most of the work if there's just one key */
266266
if (numberOfKeys==1)
267267
{
268-
/*
269-
* We treat all btree operators as strict (even if they're not so
270-
* marked in pg_proc).This means that it is impossible for an
271-
* operator condition with a NULL comparison constant to succeed, and
272-
* we can reject it right away.
273-
*
274-
* However, we now also support "x IS NULL" clauses as search
275-
* conditions, so in that case keep going.The planner has not filled
276-
* in any particular strategy in this case, so set it to
277-
* BTEqualStrategyNumber --- we can treat IS NULL as an equality
278-
* operator for purposes of search strategy.
279-
*
280-
* Likewise, "x IS NOT NULL" is supported. We treat that as either
281-
* "less than NULL" in a NULLS LAST index, or "greater than NULL"
282-
* in a NULLS FIRST index. However, we have to flip those around in
283-
* a DESC index, to allow for the re-flipping that occurs elsewhere.
284-
*/
285-
if (cur->sk_flags&SK_ISNULL)
286-
{
287-
if (cur->sk_flags&SK_SEARCHNULL)
288-
{
289-
cur->sk_strategy=BTEqualStrategyNumber;
290-
cur->sk_subtype=InvalidOid;
291-
}
292-
elseif (cur->sk_flags&SK_SEARCHNOTNULL)
293-
{
294-
switch (indoption[cur->sk_attno-1]&
295-
(INDOPTION_DESC |INDOPTION_NULLS_FIRST))
296-
{
297-
case0:/* ASC / NULLS LAST */
298-
caseINDOPTION_DESC |INDOPTION_NULLS_FIRST:
299-
cur->sk_strategy=BTLessStrategyNumber;
300-
break;
301-
default:
302-
cur->sk_strategy=BTGreaterStrategyNumber;
303-
break;
304-
}
305-
cur->sk_subtype=InvalidOid;
306-
}
307-
else
308-
so->qual_ok= false;
309-
}
310-
_bt_mark_scankey_with_indoption(cur,indoption);
268+
/* Apply indoption to scankey (might change sk_strategy!) */
269+
if (!_bt_fix_scankey_strategy(cur,indoption))
270+
so->qual_ok= false;
311271
memcpy(outkeys,cur,sizeof(ScanKeyData));
312272
so->numberOfKeys=1;
313273
/* We can mark the qual as required if it's for first index col */
@@ -340,35 +300,12 @@ _bt_preprocess_keys(IndexScanDesc scan)
340300
{
341301
if (i<numberOfKeys)
342302
{
343-
/* See comments above about NULLs and IS NULL/NOT NULL handling */
344-
/* Note: we assume SK_ISNULL is never set in a row header key */
345-
if (cur->sk_flags&SK_ISNULL)
303+
/* Apply indoption to scankey (might change sk_strategy!) */
304+
if (!_bt_fix_scankey_strategy(cur,indoption))
346305
{
347-
if (cur->sk_flags&SK_SEARCHNULL)
348-
{
349-
cur->sk_strategy=BTEqualStrategyNumber;
350-
cur->sk_subtype=InvalidOid;
351-
}
352-
elseif (cur->sk_flags&SK_SEARCHNOTNULL)
353-
{
354-
switch (indoption[cur->sk_attno-1]&
355-
(INDOPTION_DESC |INDOPTION_NULLS_FIRST))
356-
{
357-
case0:/* ASC / NULLS LAST */
358-
caseINDOPTION_DESC |INDOPTION_NULLS_FIRST:
359-
cur->sk_strategy=BTLessStrategyNumber;
360-
break;
361-
default:
362-
cur->sk_strategy=BTGreaterStrategyNumber;
363-
break;
364-
}
365-
cur->sk_subtype=InvalidOid;
366-
}
367-
else
368-
{
369-
so->qual_ok= false;
370-
return;
371-
}
306+
/* NULL can't be matched, so give up */
307+
so->qual_ok= false;
308+
return;
372309
}
373310
}
374311

@@ -480,9 +417,6 @@ _bt_preprocess_keys(IndexScanDesc scan)
480417
memset(xform,0,sizeof(xform));
481418
}
482419

483-
/* apply indoption to scankey (might change sk_strategy!) */
484-
_bt_mark_scankey_with_indoption(cur,indoption);
485-
486420
/* check strategy this key's operator corresponds to */
487421
j=cur->sk_strategy-1;
488422

@@ -678,7 +612,7 @@ _bt_compare_scankey_args(IndexScanDesc scan, ScanKey op,
678612
* indexscan initiated by syscache lookup will use cross-data-type
679613
* operators.)
680614
*
681-
* If the sk_strategy was flipped by_bt_mark_scankey_with_indoption, we
615+
* If the sk_strategy was flipped by_bt_fix_scankey_strategy, we
682616
* have to un-flip it to get the correct opfamily member.
683617
*/
684618
strat=op->sk_strategy;
@@ -708,29 +642,88 @@ _bt_compare_scankey_args(IndexScanDesc scan, ScanKey op,
708642
}
709643

710644
/*
711-
*Mark a scankey with info from the index's indoption array.
645+
*Adjust a scankey's strategy and flags setting as needed for indoptions.
712646
*
713647
* We copy the appropriate indoption value into the scankey sk_flags
714648
* (shifting to avoid clobbering system-defined flag bits). Also, if
715649
* the DESC option is set, commute (flip) the operator strategy number.
716650
*
651+
* A secondary purpose is to check for IS NULL/NOT NULL scankeys and set up
652+
* the strategy field correctly for them.
653+
*
654+
* Lastly, for ordinary scankeys (not IS NULL/NOT NULL), we check for a
655+
* NULL comparison value. Since all btree operators are assumed strict,
656+
* a NULL means that the qual cannot be satisfied. We return TRUE if the
657+
* comparison value isn't NULL, or FALSE if the scan should be abandoned.
658+
*
717659
* This function is applied to the *input* scankey structure; therefore
718660
* on a rescan we will be looking at already-processed scankeys. Hence
719661
* we have to be careful not to re-commute the strategy if we already did it.
720662
* It's a bit ugly to modify the caller's copy of the scankey but in practice
721663
* there shouldn't be any problem, since the index's indoptions are certainly
722664
* not going to change while the scankey survives.
723665
*/
724-
staticvoid
725-
_bt_mark_scankey_with_indoption(ScanKeyskey,int16*indoption)
666+
staticbool
667+
_bt_fix_scankey_strategy(ScanKeyskey,int16*indoption)
726668
{
727669
intaddflags;
728670

729671
addflags=indoption[skey->sk_attno-1] <<SK_BT_INDOPTION_SHIFT;
672+
673+
/*
674+
* We treat all btree operators as strict (even if they're not so marked
675+
* in pg_proc). This means that it is impossible for an operator condition
676+
* with a NULL comparison constant to succeed, and we can reject it right
677+
* away.
678+
*
679+
* However, we now also support "x IS NULL" clauses as search conditions,
680+
* so in that case keep going. The planner has not filled in any
681+
* particular strategy in this case, so set it to BTEqualStrategyNumber
682+
* --- we can treat IS NULL as an equality operator for purposes of search
683+
* strategy.
684+
*
685+
* Likewise, "x IS NOT NULL" is supported. We treat that as either "less
686+
* than NULL" in a NULLS LAST index, or "greater than NULL" in a NULLS
687+
* FIRST index.
688+
*/
689+
if (skey->sk_flags&SK_ISNULL)
690+
{
691+
/* SK_ISNULL shouldn't be set in a row header scankey */
692+
Assert(!(skey->sk_flags&SK_ROW_HEADER));
693+
694+
/* Set indoption flags in scankey (might be done already) */
695+
skey->sk_flags |=addflags;
696+
697+
/* Set correct strategy for IS NULL or NOT NULL search */
698+
if (skey->sk_flags&SK_SEARCHNULL)
699+
{
700+
skey->sk_strategy=BTEqualStrategyNumber;
701+
skey->sk_subtype=InvalidOid;
702+
}
703+
elseif (skey->sk_flags&SK_SEARCHNOTNULL)
704+
{
705+
if (skey->sk_flags&SK_BT_NULLS_FIRST)
706+
skey->sk_strategy=BTGreaterStrategyNumber;
707+
else
708+
skey->sk_strategy=BTLessStrategyNumber;
709+
skey->sk_subtype=InvalidOid;
710+
}
711+
else
712+
{
713+
/* regular qual, so it cannot be satisfied */
714+
return false;
715+
}
716+
717+
/* Needn't do the rest */
718+
return true;
719+
}
720+
721+
/* Adjust strategy for DESC, if we didn't already */
730722
if ((addflags&SK_BT_DESC)&& !(skey->sk_flags&SK_BT_DESC))
731723
skey->sk_strategy=BTCommuteStrategyNumber(skey->sk_strategy);
732724
skey->sk_flags |=addflags;
733725

726+
/* If it's a row header, fix row member flags and strategies similarly */
734727
if (skey->sk_flags&SK_ROW_HEADER)
735728
{
736729
ScanKeysubkey= (ScanKey)DatumGetPointer(skey->sk_argument);
@@ -747,6 +740,8 @@ _bt_mark_scankey_with_indoption(ScanKey skey, int16 *indoption)
747740
subkey++;
748741
}
749742
}
743+
744+
return true;
750745
}
751746

752747
/*

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