HOT updates. When we update a tuple without changing any of its indexed

columns, and the new version can be stored on the same heap page, we no longer
generate extra index entries for the new version.  Instead, index searches
follow the HOT-chain links to ensure they find the correct tuple version.

In addition, this patch introduces the ability to "prune" dead tuples on a
per-page basis, without having to do a complete VACUUM pass to recover space.
VACUUM is still needed to clean up dead index entries, however.

Pavan Deolasee, with help from a bunch of other people.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c
index 0009739180c..7bf1e43cb45 100644
--- a/src/backend/access/index/genam.c
+++ b/src/backend/access/index/genam.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/index/genam.c,v 1.62 2007/05/27 03:50:38 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/index/genam.c,v 1.63 2007/09/20 17:56:30 tgl Exp $
  *
  * NOTES
  *	  many of the old access method routines have been turned into
@@ -21,6 +21,7 @@
 
 #include "access/genam.h"
 #include "access/heapam.h"
+#include "access/transam.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 
@@ -95,6 +96,9 @@ RelationGetIndexScan(Relation indexRelation,
 	ItemPointerSetInvalid(&scan->xs_ctup.t_self);
 	scan->xs_ctup.t_data = NULL;
 	scan->xs_cbuf = InvalidBuffer;
+	scan->xs_prev_xmax = InvalidTransactionId;
+	scan->xs_next_hot = InvalidOffsetNumber;
+	scan->xs_hot_dead = false;
 
 	/*
 	 * Let the AM fill in the key and any opaque data it wants.