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

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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.
This commit is contained in:
Tom Lane
2007-09-20 17:56:33 +00:00
parent bbf4fdc253
commit 282d2a03dd
65 changed files with 3517 additions and 514 deletions
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8
src/backend/access/heap/hio.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/heap/hio.c,v 1.66 2007/09/12 22:10:26 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/heap/hio.c,v 1.67 2007/09/20 17:56:30 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -41,7 +41,7 @@ RelationPutHeapTuple(Relation relation,
pageHeader = BufferGetPage(buffer);
offnum = PageAddItem(pageHeader, (Item) tuple->t_data,
tuple->t_len, InvalidOffsetNumber, false);
tuple->t_len, InvalidOffsetNumber, false, true);
if (offnum == InvalidOffsetNumber)
elog(PANIC, "failed to add tuple to page");
@@ -218,7 +218,7 @@ RelationGetBufferForTuple(Relation relation, Size len,
* we're done.
*/
pageHeader = (Page) BufferGetPage(buffer);
pageFreeSpace = PageGetFreeSpace(pageHeader);
pageFreeSpace = PageGetHeapFreeSpace(pageHeader);
if (len + saveFreeSpace <= pageFreeSpace)
{
/* use this page as future insert target, too */
@@ -311,7 +311,7 @@ RelationGetBufferForTuple(Relation relation, Size len,
PageInit(pageHeader, BufferGetPageSize(buffer), 0);
if (len > PageGetFreeSpace(pageHeader))
if (len > PageGetHeapFreeSpace(pageHeader))
{
/* We should not get here given the test at the top */
elog(PANIC, "tuple is too big: size %lu", (unsigned long) len);