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, 3 deletions

diff --git a/src/backend/access/heap/rewriteheap.c b/src/backend/access/heap/rewriteheap.c
index 60aab58de38..e8c5eec50ac 100644
--- a/src/backend/access/heap/rewriteheap.c
+++ b/src/backend/access/heap/rewriteheap.c
@@ -96,7 +96,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/rewriteheap.c,v 1.6 2007/09/12 22:10:26 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/rewriteheap.c,v 1.7 2007/09/20 17:56:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -320,12 +320,14 @@ rewrite_heap_tuple(RewriteState state,
 	 * Copy the original tuple's visibility information into new_tuple.
 	 *
 	 * XXX we might later need to copy some t_infomask2 bits, too?
+	 * Right now, we intentionally clear the HOT status bits.
 	 */
 	memcpy(&new_tuple->t_data->t_choice.t_heap,
 		   &old_tuple->t_data->t_choice.t_heap,
 		   sizeof(HeapTupleFields));
 
 	new_tuple->t_data->t_infomask &= ~HEAP_XACT_MASK;
+	new_tuple->t_data->t_infomask2 &= ~HEAP2_XACT_MASK;
 	new_tuple->t_data->t_infomask |=
 		old_tuple->t_data->t_infomask & HEAP_XACT_MASK;
 
@@ -593,7 +595,7 @@ raw_heap_insert(RewriteState state, HeapTuple tup)
 	/* Now we can check to see if there's enough free space already. */
 	if (state->rs_buffer_valid)
 	{
-		pageFreeSpace = PageGetFreeSpace(page);
+		pageFreeSpace = PageGetHeapFreeSpace(page);
 
 		if (len + saveFreeSpace > pageFreeSpace)
 		{
@@ -628,7 +630,7 @@ raw_heap_insert(RewriteState state, HeapTuple tup)
 
 	/* And now we can insert the tuple into the page */
 	newoff = PageAddItem(page, (Item) heaptup->t_data, len,
-						 InvalidOffsetNumber, false);
+						 InvalidOffsetNumber, false, true);
 	if (newoff == InvalidOffsetNumber)
 		elog(ERROR, "failed to add tuple");