From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 8 Nov 2016 15:47:52 +0000 (-0500)
Subject: Improve handling of dead tuples in hash indexes.
X-Git-Tag: REL_10_BETA1~1432
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f0e72a25b05d4c29d0102fa0b892782ff193a00e;p=postgresql

Improve handling of dead tuples in hash indexes.

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.
---

diff --git a/src/backend/access/hash/hashovfl.c b/src/backend/access/hash/hashovfl.c
index db3e268a76..df7af3ec84 100644
--- a/src/backend/access/hash/hashovfl.c
+++ b/src/backend/access/hash/hashovfl.c
@@ -656,6 +656,10 @@ _hash_squeezebucket(Relation rel,
 			IndexTuple	itup;
 			Size		itemsz;
 
+			/* skip dead tuples */
+			if (ItemIdIsDead(PageGetItemId(rpage, roffnum)))
+				continue;
+
 			itup = (IndexTuple) PageGetItem(rpage,
 											PageGetItemId(rpage, roffnum));
 			itemsz = IndexTupleDSize(*itup);
diff --git a/src/backend/access/hash/hashpage.c b/src/backend/access/hash/hashpage.c
index 178463fcb6..a5e9d176a7 100644
--- a/src/backend/access/hash/hashpage.c
+++ b/src/backend/access/hash/hashpage.c
@@ -811,6 +811,10 @@ _hash_splitbucket(Relation rel,
 			Size		itemsz;
 			Bucket		bucket;
 
+			/* skip dead tuples */
+			if (ItemIdIsDead(PageGetItemId(opage, ooffnum)))
+				continue;
+
 			/*
 			 * Fetch the item's hash key (conveniently stored in the item) and
 			 * determine which bucket it now belongs in.