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Delete empty pages during GiST VACUUM.

Browse Source 
To do this, we scan GiST two times. In the first pass we make note of
empty leaf pages and internal pages. At second pass we scan through
internal pages, looking for downlinks to the empty pages.

Deleting internal pages is still not supported, like in nbtree, the last
child of an internal page is never deleted. That means that if you have a
workload where new keys are always inserted to different area than where
old keys are removed, the index will still grow without bound. But the rate
of growth will be an order of magnitude slower than before.

Author: Andrey Borodin
Discussion: https://www.postgresql.org/message-id/B1E4DF12-6CD3-4706-BDBD-BF3283328F60@yandex-team.ru
This commit is contained in:
Heikki Linnakangas
2019-03-22 13:21:20 +02:00
parent df816f6ad5
commit 7df159a620
11 changed files with 626 additions and 49 deletions
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11
src/include/access/gist_private.h
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@@ -414,12 +414,20 @@ extern bool gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
extern SplitedPageLayout *gistSplit(Relation r, Page page, IndexTuple *itup,
int len, GISTSTATE *giststate);
/* gistxlog.c */
extern XLogRecPtr gistXLogPageDelete(Buffer buffer,
TransactionId xid, Buffer parentBuffer,
OffsetNumber downlinkOffset);
extern void gistXLogPageReuse(Relation rel, BlockNumber blkno,
TransactionId latestRemovedXid);
extern XLogRecPtr gistXLogUpdate(Buffer buffer,
OffsetNumber *todelete, int ntodelete,
IndexTuple *itup, int ntup,
Buffer leftchild);
XLogRecPtr gistXLogDelete(Buffer buffer, OffsetNumber *todelete,
extern XLogRecPtr gistXLogDelete(Buffer buffer, OffsetNumber *todelete,
int ntodelete, RelFileNode hnode);
extern XLogRecPtr gistXLogSplit(bool page_is_leaf,
@@ -451,6 +459,7 @@ extern bool gistfitpage(IndexTuple *itvec, int len);
extern bool gistnospace(Page page, IndexTuple *itvec, int len, OffsetNumber todelete, Size freespace);
extern void gistcheckpage(Relation rel, Buffer buf);
extern Buffer gistNewBuffer(Relation r);
extern bool gistPageRecyclable(Page page);
extern void gistfillbuffer(Page page, IndexTuple *itup, int len,
OffsetNumber off);
extern IndexTuple *gistextractpage(Page page, int *len /* out */ );