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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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21
src/include/access/heapam.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.126 2007/06/09 18:49:55 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.127 2007/09/20 17:56:32 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -153,6 +153,10 @@ extern bool heap_fetch(Relation relation, Snapshot snapshot,
extern bool heap_release_fetch(Relation relation, Snapshot snapshot,
HeapTuple tuple, Buffer *userbuf, bool keep_buf,
Relation stats_relation);
extern bool heap_hot_search_buffer(ItemPointer tid, Buffer buffer,
Snapshot snapshot, bool *all_dead);
extern bool heap_hot_search(ItemPointer tid, Relation relation,
Snapshot snapshot, bool *all_dead);
extern void heap_get_latest_tid(Relation relation, Snapshot snapshot,
ItemPointer tid);
@@ -183,6 +187,8 @@ extern void simple_heap_update(Relation relation, ItemPointer otid,
extern void heap_markpos(HeapScanDesc scan);
extern void heap_restrpos(HeapScanDesc scan);
extern void heap_sync(Relation relation);
extern void heap_redo(XLogRecPtr lsn, XLogRecord *rptr);
extern void heap_desc(StringInfo buf, uint8 xl_info, char *rec);
extern void heap2_redo(XLogRecPtr lsn, XLogRecord *rptr);
@@ -192,7 +198,10 @@ extern XLogRecPtr log_heap_move(Relation reln, Buffer oldbuf,
ItemPointerData from,
Buffer newbuf, HeapTuple newtup);
extern XLogRecPtr log_heap_clean(Relation reln, Buffer buffer,
OffsetNumber *unused, int uncnt);
OffsetNumber *redirected, int nredirected,
OffsetNumber *nowdead, int ndead,
OffsetNumber *nowunused, int nunused,
bool redirect_move);
extern XLogRecPtr log_heap_freeze(Relation reln, Buffer buffer,
TransactionId cutoff_xid,
OffsetNumber *offsets, int offcnt);
@@ -240,7 +249,13 @@ extern MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup);
extern HeapTuple heap_addheader(int natts, bool withoid,
Size structlen, void *structure);
extern void heap_sync(Relation relation);
/* in heap/pruneheap.c */
extern void heap_page_prune_opt(Relation relation, Buffer buffer,
TransactionId OldestXmin);
extern int heap_page_prune(Relation relation, Buffer buffer,
TransactionId OldestXmin,
bool redirect_move, bool report_stats);
extern void heap_get_root_tuples(Page page, OffsetNumber *root_offsets);
/* in heap/syncscan.c */
extern void ss_report_location(Relation rel, BlockNumber location);