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Improve handling of dead tuples in hash indexes.

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When squeezing a bucket during vacuum, it's not necessary to retain
any tuples already marked as dead, so ignore them when deciding which
tuples must be moved in order to empty a bucket page.  Similarly, when
splitting a bucket, relocating dead tuples to the new bucket is a
waste of effort; instead, just ignore them.

Amit Kapila, reviewed by me.  Testing help provided by Ashutosh
Sharma.
This commit is contained in:
Robert Haas
2016-11-08 10:47:52 -05:00
parent 650b967076
commit f0e72a25b0
2 changed files with 8 additions and 0 deletions
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4
src/backend/access/hash/hashovfl.c
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@ -656,6 +656,10 @@ _hash_squeezebucket(Relation rel,
IndexTuple itup; IndexTuple itup;
Size itemsz; Size itemsz;
/* skip dead tuples */
if (ItemIdIsDead(PageGetItemId(rpage, roffnum)))
continue;
itup = (IndexTuple) PageGetItem(rpage, itup = (IndexTuple) PageGetItem(rpage,
PageGetItemId(rpage, roffnum)); PageGetItemId(rpage, roffnum));
itemsz = IndexTupleDSize(*itup); itemsz = IndexTupleDSize(*itup);

4
src/backend/access/hash/hashpage.c
View File

@ -811,6 +811,10 @@ _hash_splitbucket(Relation rel,
Size itemsz; Size itemsz;
Bucket bucket; Bucket bucket;
/* skip dead tuples */
if (ItemIdIsDead(PageGetItemId(opage, ooffnum)))
continue;
/* /*
* Fetch the item's hash key (conveniently stored in the item) and * Fetch the item's hash key (conveniently stored in the item) and
* determine which bucket it now belongs in. * determine which bucket it now belongs in.