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Improve handling of dead tuples in hash indexes.

When squeezing a bucket during vacuum, it's not necessary to retainany tuples already marked as dead, so ignore them when deciding whichtuples must be moved in order to empty a bucket page. Similarly, whensplitting a bucket, relocating dead tuples to the new bucket is awaste of effort; instead, just ignore them.Amit Kapila, reviewed by me. Testing help provided by AshutoshSharma.

1 parent650b967 commitf0e72a2Copy full SHA for f0e72a2

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src/backend/access/hash
- hashovfl.c
- hashpage.c

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`‎src/backend/access/hash/hashovfl.c`

Lines changed: 4 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -656,6 +656,10 @@ _hash_squeezebucket(Relation rel,`
`656`	`656`	`IndexTupleitup;`
`657`	`657`	`Sizeitemsz;`
`658`	`658`
	`659`	`+/* skip dead tuples */`
	`660`	`+if (ItemIdIsDead(PageGetItemId(rpage,roffnum)))`
	`661`	`+continue;`
	`662`	`+`
`659`	`663`	`itup= (IndexTuple)PageGetItem(rpage,`
`660`	`664`	`PageGetItemId(rpage,roffnum));`
`661`	`665`	`itemsz=IndexTupleDSize(*itup);`

`‎src/backend/access/hash/hashpage.c`

Lines changed: 4 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -811,6 +811,10 @@ _hash_splitbucket(Relation rel,`
`811`	`811`	`Sizeitemsz;`
`812`	`812`	`Bucketbucket;`
`813`	`813`
	`814`	`+/* skip dead tuples */`
	`815`	`+if (ItemIdIsDead(PageGetItemId(opage,ooffnum)))`
	`816`	`+continue;`
	`817`	`+`
`814`	`818`	`/*`
`815`	`819`	`* Fetch the item's hash key (conveniently stored in the item) and`
`816`	`820`	`* determine which bucket it now belongs in.`

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Commitf0e72a2

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2 files changed

2 files changed

`‎src/backend/access/hash/hashovfl.c`

`‎src/backend/access/hash/hashpage.c`

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