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Reimplement free-space-map management as per recent discussions.

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Adjustable threshold is gone in favor of keeping track of total requested
page storage and doling out proportional fractions to each relation
(with a minimum amount per relation, and some quantization of the results
to avoid thrashing with small changes in page counts).  Provide special-
case code for indexes so as not to waste space storing useless page
free space counts.  Restructure internal data storage to be a flat array
instead of list-of-chunks; this may cost a little more work in data
copying when reorganizing, but allows binary search to be used during
lookup_fsm_page_entry().
This commit is contained in:
Tom Lane
2003-03-04 21:51:22 +00:00
parent a455c94257
commit 391eb5e5b6
10 changed files with 1165 additions and 741 deletions
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42
src/backend/commands/vacuum.c
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@ -13,7 +13,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.250 2003/02/24 00:57:17 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.251 2003/03/04 21:51:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -336,6 +336,13 @@ vacuum(VacuumStmt *vacstmt)
*/
StartTransactionCommand(true);
/*
* If it was a database-wide VACUUM, print FSM usage statistics
* (we don't make you be superuser to see these).
*/
if (vacstmt->relation == NULL)
PrintFreeSpaceMapStatistics(elevel);
/*
* If we completed a database-wide VACUUM without skipping any
* relations, update the database's pg_database row with info
@ -2781,31 +2788,48 @@ vac_update_fsm(Relation onerel, VacPageList fraged_pages,
BlockNumber rel_pages)
{
int nPages = fraged_pages->num_pages;
int i;
VacPage *pagedesc = fraged_pages->pagedesc;
Size threshold;
PageFreeSpaceInfo *pageSpaces;
int outPages;
int i;
/*
* We only report pages with free space at least equal to the average
* request size --- this avoids cluttering FSM with uselessly-small bits
* of space. Although FSM would discard pages with little free space
* anyway, it's important to do this prefiltering because (a) it reduces
* the time spent holding the FSM lock in RecordRelationFreeSpace, and
* (b) FSM uses the number of pages reported as a statistic for guiding
* space management. If we didn't threshold our reports the same way
* vacuumlazy.c does, we'd be skewing that statistic.
*/
threshold = GetAvgFSMRequestSize(&onerel->rd_node);
/* +1 to avoid palloc(0) */
pageSpaces = (PageFreeSpaceInfo *)
palloc((nPages + 1) * sizeof(PageFreeSpaceInfo));
outPages = 0;
for (i = 0; i < nPages; i++)
{
pageSpaces[i].blkno = fraged_pages->pagedesc[i]->blkno;
pageSpaces[i].avail = fraged_pages->pagedesc[i]->free;
/*
* fraged_pages may contain entries for pages that we later
* decided to truncate from the relation; don't enter them into
* the free space map!
*/
if (pageSpaces[i].blkno >= rel_pages)
{
nPages = i;
if (pagedesc[i]->blkno >= rel_pages)
break;
if (pagedesc[i]->free >= threshold)
{
pageSpaces[outPages].blkno = pagedesc[i]->blkno;
pageSpaces[outPages].avail = pagedesc[i]->free;
outPages++;
}
}
MultiRecordFreeSpace(&onerel->rd_node, 0, nPages, pageSpaces);
RecordRelationFreeSpace(&onerel->rd_node, outPages, pageSpaces);
pfree(pageSpaces);
}