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Commit25b1daf

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Further optimize multi-key GIN searches.
If we're skipping past a certain TID, avoid decoding posting list segmentsthat only contain smaller TIDs.Extracted from Alexander Korotkov's fast scan patch, heavily modified.
1 parente20c70c commit25b1daf

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3 files changed

+39
-7
lines changed

3 files changed

+39
-7
lines changed

‎src/backend/access/gin/gindatapage.c‎

Lines changed: 34 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -96,19 +96,49 @@ static void dataPlaceToPageLeafSplit(Buffer buf,
9696
XLogRecData**prdata,Pagelpage,Pagerpage);
9797

9898
/*
99-
* Read all TIDs from leaf data page to single uncompressed array.
99+
* Read TIDs from leaf data page to single uncompressed array. The TIDs are
100+
* returned in ascending order.
101+
*
102+
* advancePast is a hint, indicating that the caller is only interested in
103+
* TIDs > advancePast. To return all items, use ItemPointerSetMin.
104+
*
105+
* Note: This function can still return items smaller than advancePast that
106+
* are in the same posting list as the items of interest, so the caller must
107+
* still check all the returned items. But passing it allows this function to
108+
* skip whole posting lists.
100109
*/
101110
ItemPointer
102-
GinDataLeafPageGetItems(Pagepage,int*nitems)
111+
GinDataLeafPageGetItems(Pagepage,int*nitems,ItemPointerDataadvancePast)
103112
{
104113
ItemPointerresult;
105114

106115
if (GinPageIsCompressed(page))
107116
{
108-
GinPostingList*ptr=GinDataLeafPageGetPostingList(page);
117+
GinPostingList*seg=GinDataLeafPageGetPostingList(page);
109118
Sizelen=GinDataLeafPageGetPostingListSize(page);
119+
Pointerendptr= ((Pointer)seg)+len;
120+
GinPostingList*next;
121+
122+
/* Skip to the segment containing advancePast+1 */
123+
if (ItemPointerIsValid(&advancePast))
124+
{
125+
next=GinNextPostingListSegment(seg);
126+
while ((Pointer)next<endptr&&
127+
ginCompareItemPointers(&next->first,&advancePast) <=0)
128+
{
129+
seg=next;
130+
next=GinNextPostingListSegment(seg);
131+
}
132+
len=endptr- (Pointer)seg;
133+
}
110134

111-
result=ginPostingListDecodeAllSegments(ptr,len,nitems);
135+
if (len>0)
136+
result=ginPostingListDecodeAllSegments(seg,len,nitems);
137+
else
138+
{
139+
result=NULL;
140+
*nitems=0;
141+
}
112142
}
113143
else
114144
{

‎src/backend/access/gin/ginget.c‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -400,6 +400,7 @@ startScanEntry(GinState *ginstate, GinScanEntry entry)
400400
BlockNumberrootPostingTree=GinGetPostingTree(itup);
401401
GinBtreeStack*stack;
402402
Pagepage;
403+
ItemPointerDataminItem;
403404

404405
/*
405406
* We should unlock entry page before touching posting tree to
@@ -426,7 +427,8 @@ startScanEntry(GinState *ginstate, GinScanEntry entry)
426427
/*
427428
* Load the first page into memory.
428429
*/
429-
entry->list=GinDataLeafPageGetItems(page,&entry->nlist);
430+
ItemPointerSetMin(&minItem);
431+
entry->list=GinDataLeafPageGetItems(page,&entry->nlist,minItem);
430432

431433
entry->predictNumberResult=stack->predictNumber*entry->nlist;
432434

@@ -558,7 +560,7 @@ entryLoadMoreItems(GinState *ginstate, GinScanEntry entry, ItemPointerData advan
558560
continue;
559561
}
560562

561-
entry->list=GinDataLeafPageGetItems(page,&entry->nlist);
563+
entry->list=GinDataLeafPageGetItems(page,&entry->nlist,advancePast);
562564

563565
for (i=0;i<entry->nlist;i++)
564566
{

‎src/include/access/gin_private.h‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -692,7 +692,7 @@ extern ItemPointer ginReadTuple(GinState *ginstate, OffsetNumber attnum,
692692
IndexTupleitup,int*nitems);
693693

694694
/* gindatapage.c */
695-
externItemPointerGinDataLeafPageGetItems(Pagepage,int*nitems);
695+
externItemPointerGinDataLeafPageGetItems(Pagepage,int*nitems,ItemPointerDataadvancePast);
696696
externintGinDataLeafPageGetItemsToTbm(Pagepage,TIDBitmap*tbm);
697697
externBlockNumbercreatePostingTree(Relationindex,
698698
ItemPointerData*items,uint32nitems,

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