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Trivial patch to double vacuum speed on tables with no indexes (prevent

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second scan of table).

Gregory Stark
This commit is contained in:
Bruce Momjian 2006-09-04 21:40:23 +00:00
parent c66939c4aa
commit ed8969b187
1 changed files with 33 additions and 12 deletions
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33
src/backend/commands/vacuumlazy.c
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@ -16,6 +16,10 @@
* perform a pass of index cleanup and page compaction, then resume the heap
* scan with an empty TID array.
*
* As a special exception if we're processing a table with no indexes we can
* vacuum each page as we go so we don't need to allocate more space than
* enough to hold as many heap tuples fit on one page.
*
* We can limit the storage for page free space to MaxFSMPages entries,
* since that's the most the free space map will be willing to remember
* anyway. If the relation has fewer than that many pages with free space,
@ -31,7 +35,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.76 2006/07/31 20:09:00 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.77 2006/09/04 21:40:23 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -106,7 +110,7 @@ static void lazy_truncate_heap(Relation onerel, LVRelStats *vacrelstats,
TransactionId OldestXmin);
static BlockNumber count_nondeletable_pages(Relation onerel,
LVRelStats *vacrelstats, TransactionId OldestXmin);
static void lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks);
static void lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks, unsigned nindexes);
static void lazy_record_dead_tuple(LVRelStats *vacrelstats,
ItemPointer itemptr);
static void lazy_record_free_space(LVRelStats *vacrelstats,
@ -206,7 +210,8 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
* This routine sets commit status bits, builds lists of dead tuples
* and pages with free space, and calculates statistics on the number
* of live tuples in the heap. When done, or when we run low on space
* for dead-tuple TIDs, invoke vacuuming of indexes and heap.
* for dead-tuple TIDs, or after every page if the table has no indexes
* invoke vacuuming of indexes and heap.
*
* It also updates the minimum Xid found anywhere on the table in
* vacrelstats->minxid, for later storing it in pg_class.relminxid.
@ -247,7 +252,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
vacrelstats->rel_pages = nblocks;
vacrelstats->nonempty_pages = 0;
lazy_space_alloc(vacrelstats, nblocks);
lazy_space_alloc(vacrelstats, nblocks, nindexes);
for (blkno = 0; blkno < nblocks; blkno++)
{
@ -282,8 +287,14 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
buf = ReadBuffer(onerel, blkno);
/* In this phase we only need shared access to the buffer */
/* In this phase we only need shared access to the buffer unless we're
* going to do the vacuuming now which we do if there are no indexes
*/
if (nindexes)
LockBuffer(buf, BUFFER_LOCK_SHARE);
else
LockBufferForCleanup(buf);
page = BufferGetPage(buf);
@ -450,6 +461,12 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
{
lazy_record_free_space(vacrelstats, blkno,
PageGetFreeSpace(page));
} else if (!nindexes) {
/* If there are no indexes we can vacuum the page right now instead
* of doing a second scan */
lazy_vacuum_page(onerel, blkno, buf, 0, vacrelstats);
lazy_record_free_space(vacrelstats, blkno, PageGetFreeSpace(BufferGetPage(buf)));
vacrelstats->num_dead_tuples = 0;
}
/* Remember the location of the last page with nonremovable tuples */
@ -891,16 +908,20 @@ count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats,
* See the comments at the head of this file for rationale.
*/
static void
lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks)
lazy_space_alloc(LVRelStats *vacrelstats, BlockNumber relblocks, unsigned nindexes)
{
long maxtuples;
int maxpages;
if (nindexes) {
maxtuples = (maintenance_work_mem * 1024L) / sizeof(ItemPointerData);
maxtuples = Min(maxtuples, INT_MAX);
maxtuples = Min(maxtuples, MaxAllocSize / sizeof(ItemPointerData));
/* stay sane if small maintenance_work_mem */
maxtuples = Max(maxtuples, MaxHeapTuplesPerPage);
} else {
maxtuples = MaxHeapTuplesPerPage;
}
vacrelstats->num_dead_tuples = 0;
vacrelstats->max_dead_tuples = (int) maxtuples;