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Commit329a532

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Fix infinite loop while checking of partial match in pending list.
Improve comments. Now GIN-indexable operators should be strict.Per Tom's questions/suggestions.
1 parent27fbfd3 commit329a532

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2 files changed

+85
-15
lines changed

2 files changed

+85
-15
lines changed

‎src/backend/access/gin/ginget.c

Lines changed: 76 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
1010
* IDENTIFICATION
11-
*$PostgreSQL: pgsql/src/backend/access/gin/ginget.c,v 1.24 2009/03/25 22:19:01tgl Exp $
11+
*$PostgreSQL: pgsql/src/backend/access/gin/ginget.c,v 1.25 2009/04/05 11:32:01teodor Exp $
1212
*-------------------------------------------------------------------------
1313
*/
1414

@@ -618,6 +618,7 @@ entryGetItem(Relation index, GinScanEntry entry)
618618
* Sets key->curItem to new found heap item pointer for one scan key
619619
* Returns isFinished, ie TRUE means we did NOT get a new item pointer!
620620
* Also, *keyrecheck is set true if recheck is needed for this scan key.
621+
* Note: lossy page could be returned after items from the same page.
621622
*/
622623
staticbool
623624
keyGetItem(Relationindex,GinState*ginstate,MemoryContexttempCtx,
@@ -635,7 +636,10 @@ keyGetItem(Relation index, GinState *ginstate, MemoryContext tempCtx,
635636
{
636637
/*
637638
* move forward from previously value and set new curItem, which is
638-
* minimal from entries->curItems
639+
* minimal from entries->curItems. Lossy page is encoded by ItemPointer
640+
* with max value for offset (0xffff), so if there is an non-lossy entries
641+
* on lossy page they will returned too and after that the whole page.
642+
* That's not a problem for resulting tidbitmap.
639643
*/
640644
ItemPointerSetMax(&key->curItem);
641645
for (i=0;i<key->nentries;i++)
@@ -646,7 +650,8 @@ keyGetItem(Relation index, GinState *ginstate, MemoryContext tempCtx,
646650
{
647651
/*
648652
* Move forward only entries which was the least
649-
* on previous call
653+
* on previous call, key->entryRes[i] points that
654+
* current entry was a result of loop/call.
650655
*/
651656
if (entry->isFinished== FALSE&&entryGetItem(index,entry)== FALSE)
652657
{
@@ -671,11 +676,21 @@ keyGetItem(Relation index, GinState *ginstate, MemoryContext tempCtx,
671676
}
672677

673678
/*
679+
* Now key->curItem contains closest ItemPointer to previous result.
680+
*
674681
* if key->nentries == 1 then the consistentFn should always succeed,
675682
* but we must call it anyway to find out the recheck status.
676683
*/
677684

678-
/* setting up array for consistentFn */
685+
/*----------
686+
* entryRes array is used for:
687+
* - as an argument for consistentFn
688+
* - entry->curItem with corresponding key->entryRes[i] == false are
689+
* greater than key->curItem, so next loop/call they should be
690+
* renewed by entryGetItem(). So, we need to set up an array before
691+
* checking of lossy page.
692+
*----------
693+
*/
679694
for (i=0;i<key->nentries;i++)
680695
{
681696
entry=key->scanEntry+i;
@@ -719,7 +734,10 @@ keyGetItem(Relation index, GinState *ginstate, MemoryContext tempCtx,
719734

720735
/*
721736
* Get ItemPointer of next heap row to be checked from pending list.
722-
* Returns false if there are no more.
737+
* Returns false if there are no more. On pages with several rows
738+
* it returns each row separately, on page with part of heap row returns
739+
* per page data. pos->firstOffset and pos->lastOffset points
740+
* fraction of tuples for current heap row.
723741
*
724742
* The pendingBuffer is presumed pinned and share-locked on entry, and is
725743
* pinned and share-locked on success exit. On failure exit it's released.
@@ -787,13 +805,26 @@ scanGetCandidate(IndexScanDesc scan, pendingPosition *pos)
787805
*/
788806
pos->lastOffset=maxoff+1;
789807
}
808+
809+
/*
810+
* Now pos->firstOffset points to the first tuple of current heap row,
811+
* pos->lastOffset points to the first tuple of second heap row (or
812+
* to the end of page)
813+
*/
814+
790815
break;
791816
}
792817
}
793818

794819
return true;
795820
}
796821

822+
/*
823+
* Scan page from current tuple (off) up to the first event:
824+
* - tuple's attribute number is not equal to entry's attrnum
825+
* - reach of last tuple
826+
* - match is found (then returns true)
827+
*/
797828
staticbool
798829
matchPartialInPendingList(GinState*ginstate,Pagepage,
799830
OffsetNumberoff,OffsetNumbermaxoff,
@@ -817,6 +848,13 @@ matchPartialInPendingList(GinState *ginstate, Page page,
817848
datumExtracted[off-1 ]= true;
818849
}
819850

851+
/*----------
852+
* Check of partial match.
853+
* case cmp == 0 => match
854+
* case cmp > 0 => not match and finish scan
855+
* case cmp < 0 => not match and continue scan
856+
*----------
857+
*/
820858
cmp=DatumGetInt32(FunctionCall4(&ginstate->comparePartialFn[attrnum],
821859
value,
822860
datum[off-1],
@@ -826,14 +864,16 @@ matchPartialInPendingList(GinState *ginstate, Page page,
826864
return true;
827865
elseif (cmp>0)
828866
return false;
867+
868+
off++;
829869
}
830870

831871
return false;
832872
}
833873

834874
/*
835875
* Sets entryRes array for each key by looking at
836-
* every entry per indexed value (row) in pending list.
876+
* every entry per indexed value (heap'srow) in pending list.
837877
* returns true if at least one of datum was matched by key's entry
838878
*
839879
* The pendingBuffer is presumed pinned and share-locked on entry.
@@ -878,9 +918,15 @@ collectDatumForItem(IndexScanDesc scan, pendingPosition *pos)
878918
StopMiddle;
879919
GinScanEntryentry=key->scanEntry+j;
880920

921+
/* already true - do not extra work */
881922
if (key->entryRes[j] )
882923
continue;
883924

925+
/*
926+
* Interested tuples are from pos->firstOffset to pos->lastOffset
927+
* and they are ordered by (attnum, Datum) as it's done in entry tree
928+
* So we could use binary search to prevent linear scanning
929+
*/
884930
while (StopLow<StopHigh)
885931
{
886932
StopMiddle=StopLow+ ((StopHigh-StopLow) >>1);
@@ -908,6 +954,11 @@ collectDatumForItem(IndexScanDesc scan, pendingPosition *pos)
908954

909955
if (res==0 )
910956
{
957+
/*
958+
* The exact match causes, so we just scan from
959+
* current position to find a partial match.
960+
* See comment above about tuple's ordering.
961+
*/
911962
if (entry->isPartialMatch )
912963
key->entryRes[j]=
913964
matchPartialInPendingList(&so->ginstate,
@@ -931,6 +982,12 @@ collectDatumForItem(IndexScanDesc scan, pendingPosition *pos)
931982
}
932983

933984
if (StopLow>=StopHigh&&entry->isPartialMatch )
985+
{
986+
/*
987+
* The exact match wasn't found, so we need to start
988+
* scan from first tuple greater then current entry
989+
* See comment above about tuple's ordering.
990+
*/
934991
key->entryRes[j]=
935992
matchPartialInPendingList(&so->ginstate,
936993
page,StopHigh,
@@ -941,6 +998,7 @@ collectDatumForItem(IndexScanDesc scan, pendingPosition *pos)
941998
datumExtracted,
942999
entry->strategy,
9431000
entry->extra_data);
1001+
}
9441002

9451003
hasMatch |=key->entryRes[j];
9461004
}
@@ -960,6 +1018,11 @@ collectDatumForItem(IndexScanDesc scan, pendingPosition *pos)
9601018
{
9611019
ItemPointerDataitem=pos->item;
9621020

1021+
/*
1022+
* need to get next portion of tuples of row containing
1023+
* on several pages
1024+
*/
1025+
9631026
if (scanGetCandidate(scan,pos)== false|| !ItemPointerEquals(&pos->item,&item) )
9641027
elog(ERROR,"Could not process tuple");/* XXX should not be here ! */
9651028
}
@@ -1004,19 +1067,23 @@ scanPendingInsert(IndexScanDesc scan, TIDBitmap *tbm, int64 *ntids)
10041067
UnlockReleaseBuffer(metabuffer );
10051068

10061069
/*
1007-
* loop for each heap row
1070+
* loop for each heap row. scanGetCandidate returns full row
1071+
* or row's tuples from first page.
10081072
*/
10091073
while(scanGetCandidate(scan,&pos) )
10101074
{
10111075

10121076
/*
1013-
* Check entries in rows and setup entryRes array
1077+
* Check entries in tuple and setup entryRes array
1078+
* If tuples of heap's row are placed on several pages
1079+
* collectDatumForItem will read all of that pages.
10141080
*/
10151081
if (!collectDatumForItem(scan,&pos))
10161082
continue;
10171083

10181084
/*
1019-
* check for consistent
1085+
* Matching of entries of one row is finished,
1086+
* so check row by consistent function.
10201087
*/
10211088
oldCtx=MemoryContextSwitchTo(so->tempCtx);
10221089
recheck= false;

‎src/backend/access/gin/ginscan.c

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
1010
* IDENTIFICATION
11-
*$PostgreSQL: pgsql/src/backend/access/gin/ginscan.c,v 1.22 2009/03/25 22:19:01tgl Exp $
11+
*$PostgreSQL: pgsql/src/backend/access/gin/ginscan.c,v 1.23 2009/04/05 11:32:01teodor Exp $
1212
*-------------------------------------------------------------------------
1313
*/
1414

@@ -175,12 +175,15 @@ newScanKey(IndexScanDesc scan)
175175
bool*partial_matches=NULL;
176176
Pointer*extra_data=NULL;
177177

178-
/* XXX can't we treat nulls by just setting isVoidRes? */
179-
/* This would amount to assuming that all GIN operators are strict */
178+
/*
179+
* Assume, that GIN-indexable operators are strict, so
180+
* nothing could be found
181+
*/
180182
if (skey->sk_flags&SK_ISNULL)
181-
ereport(ERROR,
182-
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
183-
errmsg("GIN indexes do not support NULL scan keys")));
183+
{
184+
so->isVoidRes= true;
185+
break;
186+
}
184187

185188
entryValues= (Datum*)
186189
DatumGetPointer(FunctionCall5(&so->ginstate.extractQueryFn[skey->sk_attno-1],

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