Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum - Mailing list pgsql-hackers
| From | Tom Lane |
|---|---|
| Subject | Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum |
| Date | |
| Msg-id | 28116.1306609295@sss.pgh.pa.us Whole thread Raw |
| In response to | Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum (Robert Haas <robertmhaas@gmail.com>) |
| Responses |
Re: [ADMIN] pg_class reltuples/relpages not updated by autovacuum/vacuum
(Greg Stark <gsstark@mit.edu>)
|
| List | pgsql-hackers |
Robert Haas <robertmhaas@gmail.com> writes:
> Still, maybe we don't have a better option. If it were me, I'd add an
> additional safety valve: use your formula if the percentage of the
> relation scanned is above some threshold where there's unlikely to be
> too much skew. But if the percentage scanned is too small, then don't
> use that formula. Instead, only update relpages/reltuples if the
> relation is now larger; set relpages to the new actual value, and
> scale up reltuples proportionately.
> However, I just work here. It's possible that I'm worrying about a
> problem that won't materialize in practice.
Attached is a proposed patch to fix these issues. Experimentation
convinced me that including a fudge factor for VACUUM's results made
things *less* accurate, not more so. The reason seems to be bound up in
Greg Stark's observation that the unmodified calculation is equivalent
to assuming that the old average tuple density still applies to the
unscanned pages. In a VACUUM, we know that the unscanned pages are
exactly those that have had no changes since (at least) the last vacuum,
which means that indeed the old density ought to be a good estimate.
Now, this reasoning can break down if the table's tuple density is
nonuniform, but what I found in my testing is that if you vacuum after a
significant change in a table (such as deleting a lot of rows), and you
don't apply the full unfudged correction, you get a badly wrong result.
I think that's a more significant issue than the possibility of drift
over time.
I also found that Greg was right in thinking that it would help if we
tweaked lazy_scan_heap to not always scan the first
SKIP_PAGES_THRESHOLD-1 pages even if they were
all_visible_according_to_vm. That seemed to skew the results if those
pages weren't representative. And, for the case of a useless manual
vacuum on a completely clean table, it would cause the reltuples value
to drift when there was no reason to change it at all.
Lastly, this patch removes a bunch of grotty interconnections between
VACUUM and ANALYZE that were meant to prevent ANALYZE from updating the
stats if VACUUM had done a full-table scan in the same command. With
the new logic it's relatively harmless if ANALYZE does that, and anyway
autovacuum frequently fires the two cases independently anyway, making
all that logic quite useless in the normal case. (This simplification
accounts for the bulk of the diff, actually.)
Comments?
regards, tom lane
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 0568a1bcf86281a9b1086d343e7027557295065c..fa84989fc6fa8be90d4eecb9c33e94a232d79880 100644
*** a/src/backend/commands/analyze.c
--- b/src/backend/commands/analyze.c
*************** static MemoryContext anl_context = NULL;
*** 84,91 ****
static BufferAccessStrategy vac_strategy;
! static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
! bool update_reltuples, bool inh);
static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
int samplesize);
static bool BlockSampler_HasMore(BlockSampler bs);
--- 84,90 ----
static BufferAccessStrategy vac_strategy;
! static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt, bool inh);
static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
int samplesize);
static bool BlockSampler_HasMore(BlockSampler bs);
*************** static bool std_typanalyze(VacAttrStats
*** 115,132 ****
/*
* analyze_rel() -- analyze one relation
- *
- * If update_reltuples is true, we update reltuples and relpages columns
- * in pg_class. Caller should pass false if we're part of VACUUM ANALYZE,
- * and the VACUUM didn't skip any pages. We only have an approximate count,
- * so we don't want to overwrite the accurate values already inserted by the
- * VACUUM in that case. VACUUM always scans all indexes, however, so the
- * pg_class entries for indexes are never updated if we're part of VACUUM
- * ANALYZE.
*/
void
! analyze_rel(Oid relid, VacuumStmt *vacstmt,
! BufferAccessStrategy bstrategy, bool update_reltuples)
{
Relation onerel;
--- 114,122 ----
/*
* analyze_rel() -- analyze one relation
*/
void
! analyze_rel(Oid relid, VacuumStmt *vacstmt, BufferAccessStrategy bstrategy)
{
Relation onerel;
*************** analyze_rel(Oid relid, VacuumStmt *vacst
*** 238,250 ****
/*
* Do the normal non-recursive ANALYZE.
*/
! do_analyze_rel(onerel, vacstmt, update_reltuples, false);
/*
* If there are child tables, do recursive ANALYZE.
*/
if (onerel->rd_rel->relhassubclass)
! do_analyze_rel(onerel, vacstmt, false, true);
/*
* Close source relation now, but keep lock so that no one deletes it
--- 228,240 ----
/*
* Do the normal non-recursive ANALYZE.
*/
! do_analyze_rel(onerel, vacstmt, false);
/*
* If there are child tables, do recursive ANALYZE.
*/
if (onerel->rd_rel->relhassubclass)
! do_analyze_rel(onerel, vacstmt, true);
/*
* Close source relation now, but keep lock so that no one deletes it
*************** analyze_rel(Oid relid, VacuumStmt *vacst
*** 267,274 ****
* do_analyze_rel() -- analyze one relation, recursively or not
*/
static void
! do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
! bool update_reltuples, bool inh)
{
int attr_cnt,
tcnt,
--- 257,263 ----
* do_analyze_rel() -- analyze one relation, recursively or not
*/
static void
! do_analyze_rel(Relation onerel, VacuumStmt *vacstmt, bool inh)
{
int attr_cnt,
tcnt,
*************** do_analyze_rel(Relation onerel, VacuumSt
*** 437,445 ****
}
/*
! * Quit if no analyzable columns and no pg_class update needed.
*/
! if (attr_cnt <= 0 && !analyzableindex && !update_reltuples)
goto cleanup;
/*
--- 426,434 ----
}
/*
! * Quit if no analyzable columns.
*/
! if (attr_cnt <= 0 && !analyzableindex)
goto cleanup;
/*
*************** do_analyze_rel(Relation onerel, VacuumSt
*** 549,558 ****
}
/*
! * Update pages/tuples stats in pg_class, but not if we're inside a VACUUM
! * that got a more precise number.
*/
! if (update_reltuples)
vac_update_relstats(onerel,
RelationGetNumberOfBlocks(onerel),
totalrows, hasindex, InvalidTransactionId);
--- 538,547 ----
}
/*
! * Update pages/tuples stats in pg_class ... but not if we're doing
! * inherited stats.
*/
! if (!inh)
vac_update_relstats(onerel,
RelationGetNumberOfBlocks(onerel),
totalrows, hasindex, InvalidTransactionId);
*************** do_analyze_rel(Relation onerel, VacuumSt
*** 562,568 ****
* VACUUM ANALYZE, don't overwrite the accurate count already inserted by
* VACUUM.
*/
! if (!(vacstmt->options & VACOPT_VACUUM))
{
for (ind = 0; ind < nindexes; ind++)
{
--- 551,557 ----
* VACUUM ANALYZE, don't overwrite the accurate count already inserted by
* VACUUM.
*/
! if (!inh && !(vacstmt->options & VACOPT_VACUUM))
{
for (ind = 0; ind < nindexes; ind++)
{
*************** do_analyze_rel(Relation onerel, VacuumSt
*** 577,589 ****
}
/*
! * Report ANALYZE to the stats collector, too; likewise, tell it to adopt
! * these numbers only if we're not inside a VACUUM that got a better
! * number. However, a call with inh = true shouldn't reset the stats.
*/
if (!inh)
! pgstat_report_analyze(onerel, update_reltuples,
! totalrows, totaldeadrows);
/* We skip to here if there were no analyzable columns */
cleanup:
--- 566,577 ----
}
/*
! * Report ANALYZE to the stats collector, too. However, if doing
! * inherited stats we shouldn't report, because the stats collector only
! * tracks per-table stats.
*/
if (!inh)
! pgstat_report_analyze(onerel, totalrows, totaldeadrows);
/* We skip to here if there were no analyzable columns */
cleanup:
*************** acquire_sample_rows(Relation onerel, Hea
*** 1243,1260 ****
qsort((void *) rows, numrows, sizeof(HeapTuple), compare_rows);
/*
! * Estimate total numbers of rows in relation.
*/
if (bs.m > 0)
! {
! *totalrows = floor((liverows * totalblocks) / bs.m + 0.5);
! *totaldeadrows = floor((deadrows * totalblocks) / bs.m + 0.5);
! }
else
- {
- *totalrows = 0.0;
*totaldeadrows = 0.0;
- }
/*
* Emit some interesting relation info
--- 1231,1249 ----
qsort((void *) rows, numrows, sizeof(HeapTuple), compare_rows);
/*
! * Estimate total numbers of rows in relation. For live rows, use
! * vac_estimate_reltuples; for dead rows, we have no source of old
! * information, so we have to assume the density is the same in unseen
! * pages as in the pages we scanned.
*/
+ *totalrows = vac_estimate_reltuples(onerel, true,
+ totalblocks,
+ bs.m,
+ liverows);
if (bs.m > 0)
! *totaldeadrows = floor((deadrows / bs.m) * totalblocks + 0.5);
else
*totaldeadrows = 0.0;
/*
* Emit some interesting relation info
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 9606569617afafe16c55752183cb2a6de89bcad1..efae31acab7de0f6d4cbe45fb175a301486ce582 100644
*** a/src/backend/commands/vacuum.c
--- b/src/backend/commands/vacuum.c
***************
*** 20,25 ****
--- 20,27 ----
*/
#include "postgres.h"
+ #include <math.h>
+
#include "access/clog.h"
#include "access/genam.h"
#include "access/heapam.h"
*************** static BufferAccessStrategy vac_strategy
*** 62,68 ****
static List *get_rel_oids(Oid relid, const RangeVar *vacrel);
static void vac_truncate_clog(TransactionId frozenXID);
static bool vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast,
! bool for_wraparound, bool *scanned_all);
/*
--- 64,70 ----
static List *get_rel_oids(Oid relid, const RangeVar *vacrel);
static void vac_truncate_clog(TransactionId frozenXID);
static bool vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast,
! bool for_wraparound);
/*
*************** vacuum(VacuumStmt *vacstmt, Oid relid, b
*** 219,230 ****
foreach(cur, relations)
{
Oid relid = lfirst_oid(cur);
- bool scanned_all = false;
if (vacstmt->options & VACOPT_VACUUM)
{
! if (!vacuum_rel(relid, vacstmt, do_toast, for_wraparound,
! &scanned_all))
continue;
}
--- 221,230 ----
foreach(cur, relations)
{
Oid relid = lfirst_oid(cur);
if (vacstmt->options & VACOPT_VACUUM)
{
! if (!vacuum_rel(relid, vacstmt, do_toast, for_wraparound))
continue;
}
*************** vacuum(VacuumStmt *vacstmt, Oid relid, b
*** 241,247 ****
PushActiveSnapshot(GetTransactionSnapshot());
}
! analyze_rel(relid, vacstmt, vac_strategy, !scanned_all);
if (use_own_xacts)
{
--- 241,247 ----
PushActiveSnapshot(GetTransactionSnapshot());
}
! analyze_rel(relid, vacstmt, vac_strategy);
if (use_own_xacts)
{
*************** vacuum_set_xid_limits(int freeze_min_age
*** 454,459 ****
--- 454,537 ----
/*
+ * vac_estimate_reltuples() -- estimate the new value for pg_class.reltuples
+ *
+ * If we scanned the whole relation then we should just use the count of
+ * live tuples seen; but if we did not, we should not trust the count
+ * unreservedly, especially not in VACUUM, which may have scanned a quite
+ * nonrandom subset of the table. When we have only partial information,
+ * we take the old value of pg_class.reltuples as a measurement of the
+ * tuple density in the unscanned pages.
+ *
+ * This routine is shared by VACUUM and ANALYZE.
+ */
+ double
+ vac_estimate_reltuples(Relation relation, bool is_analyze,
+ BlockNumber total_pages,
+ BlockNumber scanned_pages,
+ double scanned_tuples)
+ {
+ BlockNumber old_rel_pages = relation->rd_rel->relpages;
+ double old_rel_tuples = relation->rd_rel->reltuples;
+ double old_density;
+ double new_density;
+ double multiplier;
+ double updated_density;
+
+ /* If we did scan the whole table, just use the count as-is */
+ if (scanned_pages >= total_pages)
+ return scanned_tuples;
+
+ /*
+ * If scanned_pages is zero but total_pages isn't, keep the existing
+ * value of reltuples.
+ */
+ if (scanned_pages == 0)
+ return old_rel_tuples;
+
+ /*
+ * If old value of relpages is zero, old density is indeterminate; we
+ * can't do much except scale up scanned_tuples to match total_pages.
+ */
+ if (old_rel_pages == 0)
+ return floor((scanned_tuples / scanned_pages) * total_pages + 0.5);
+
+ /*
+ * Okay, we've covered the corner cases. The normal calculation is to
+ * convert the old measurement to a density (tuples per page), then
+ * update the density using an exponential-moving-average approach,
+ * and finally compute reltuples as updated_density * total_pages.
+ *
+ * For ANALYZE, the moving average multiplier is just the fraction of
+ * the table's pages we scanned. This is equivalent to assuming
+ * that the tuple density in the unscanned pages didn't change. Of
+ * course, it probably did, if the new density measurement is different.
+ * But over repeated cycles, the value of reltuples will converge towards
+ * the correct value, if repeated measurements show the same new density.
+ *
+ * For VACUUM, the situation is a bit different: we have looked at a
+ * nonrandom sample of pages, but we know for certain that the pages we
+ * didn't look at are precisely the ones that haven't changed lately.
+ * Thus, there is a reasonable argument for doing exactly the same thing
+ * as for the ANALYZE case, that is use the old density measurement as
+ * the value for the unscanned pages.
+ *
+ * This logic could probably use further refinement.
+ */
+ old_density = old_rel_tuples / old_rel_pages;
+ new_density = scanned_tuples / scanned_pages;
+ multiplier = (double) scanned_pages / (double) total_pages;
+ #ifdef NOT_USED
+ /* this makes things less accurate, not more so :-( */
+ if (!is_analyze && multiplier < 0.5)
+ multiplier *= 0.25; /* apply fudge factor */
+ #endif
+ updated_density = old_density + (new_density - old_density) * multiplier;
+ return floor(updated_density * total_pages + 0.5);
+ }
+
+
+ /*
* vac_update_relstats() -- update statistics for one relation
*
* Update the whole-relation statistics that are kept in its pg_class
*************** vacuum_set_xid_limits(int freeze_min_age
*** 480,486 ****
* somebody vacuuming pg_class might think they could delete a tuple
* marked with xmin = our xid.
*
! * This routine is shared by VACUUM and stand-alone ANALYZE.
*/
void
vac_update_relstats(Relation relation,
--- 558,564 ----
* somebody vacuuming pg_class might think they could delete a tuple
* marked with xmin = our xid.
*
! * This routine is shared by VACUUM and ANALYZE.
*/
void
vac_update_relstats(Relation relation,
*************** vac_truncate_clog(TransactionId frozenXI
*** 758,771 ****
* many small transactions. Otherwise, two-phase locking would require
* us to lock the entire database during one pass of the vacuum cleaner.
*
- * We'll return true in *scanned_all if the vacuum scanned all heap
- * pages, and updated pg_class.
- *
* At entry and exit, we are not inside a transaction.
*/
static bool
! vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
! bool *scanned_all)
{
LOCKMODE lmode;
Relation onerel;
--- 836,845 ----
* many small transactions. Otherwise, two-phase locking would require
* us to lock the entire database during one pass of the vacuum cleaner.
*
* At entry and exit, we are not inside a transaction.
*/
static bool
! vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound)
{
LOCKMODE lmode;
Relation onerel;
*************** vacuum_rel(Oid relid, VacuumStmt *vacstm
*** 775,783 ****
int save_sec_context;
int save_nestlevel;
- if (scanned_all)
- *scanned_all = false;
-
/* Begin a transaction for vacuuming this relation */
StartTransactionCommand();
--- 849,854 ----
*************** vacuum_rel(Oid relid, VacuumStmt *vacstm
*** 971,977 ****
vacstmt->freeze_min_age, vacstmt->freeze_table_age);
}
else
! lazy_vacuum_rel(onerel, vacstmt, vac_strategy, scanned_all);
/* Roll back any GUC changes executed by index functions */
AtEOXact_GUC(false, save_nestlevel);
--- 1042,1048 ----
vacstmt->freeze_min_age, vacstmt->freeze_table_age);
}
else
! lazy_vacuum_rel(onerel, vacstmt, vac_strategy);
/* Roll back any GUC changes executed by index functions */
AtEOXact_GUC(false, save_nestlevel);
*************** vacuum_rel(Oid relid, VacuumStmt *vacstm
*** 997,1003 ****
* totally unimportant for toast relations.
*/
if (toast_relid != InvalidOid)
! vacuum_rel(toast_relid, vacstmt, false, for_wraparound, NULL);
/*
* Now release the session-level lock on the master table.
--- 1068,1074 ----
* totally unimportant for toast relations.
*/
if (toast_relid != InvalidOid)
! vacuum_rel(toast_relid, vacstmt, false, for_wraparound);
/*
* Now release the session-level lock on the master table.
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
index 9393fa0727aaad7508e1163623322b4066412257..570f1032f3d4eba46ed54de3f6cd39d62e6d09f0 100644
*** a/src/backend/commands/vacuumlazy.c
--- b/src/backend/commands/vacuumlazy.c
***************
*** 77,93 ****
* Before we consider skipping a page that's marked as clean in
* visibility map, we must've seen at least this many clean pages.
*/
! #define SKIP_PAGES_THRESHOLD 32
typedef struct LVRelStats
{
/* hasindex = true means two-pass strategy; false means one-pass */
bool hasindex;
- bool scanned_all; /* have we scanned all pages (this far)? */
/* Overall statistics about rel */
! BlockNumber rel_pages;
double old_rel_tuples; /* previous value of pg_class.reltuples */
! double rel_tuples; /* counts only tuples on scanned pages */
BlockNumber pages_removed;
double tuples_deleted;
BlockNumber nonempty_pages; /* actually, last nonempty page + 1 */
--- 77,94 ----
* Before we consider skipping a page that's marked as clean in
* visibility map, we must've seen at least this many clean pages.
*/
! #define SKIP_PAGES_THRESHOLD ((BlockNumber) 32)
typedef struct LVRelStats
{
/* hasindex = true means two-pass strategy; false means one-pass */
bool hasindex;
/* Overall statistics about rel */
! BlockNumber rel_pages; /* total number of pages */
! BlockNumber scanned_pages; /* number of pages we examined */
! double scanned_tuples; /* counts only tuples on scanned pages */
double old_rel_tuples; /* previous value of pg_class.reltuples */
! double new_rel_tuples; /* new estimated total # of tuples */
BlockNumber pages_removed;
double tuples_deleted;
BlockNumber nonempty_pages; /* actually, last nonempty page + 1 */
*************** static int vac_cmp_itemptr(const void *l
*** 143,149 ****
*/
void
lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
! BufferAccessStrategy bstrategy, bool *scanned_all)
{
LVRelStats *vacrelstats;
Relation *Irel;
--- 144,150 ----
*/
void
lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
! BufferAccessStrategy bstrategy)
{
LVRelStats *vacrelstats;
Relation *Irel;
*************** lazy_vacuum_rel(Relation onerel, VacuumS
*** 175,181 ****
vacrelstats = (LVRelStats *) palloc0(sizeof(LVRelStats));
- vacrelstats->scanned_all = true; /* will be cleared if we skip a page */
vacrelstats->old_rel_tuples = onerel->rd_rel->reltuples;
vacrelstats->num_index_scans = 0;
--- 176,181 ----
*************** lazy_vacuum_rel(Relation onerel, VacuumS
*** 205,228 ****
FreeSpaceMapVacuum(onerel);
/*
! * Update statistics in pg_class. But only if we didn't skip any pages;
! * the tuple count only includes tuples from the pages we've visited, and
! * we haven't frozen tuples in unvisited pages either. The page count is
! * accurate in any case, but because we use the reltuples / relpages ratio
! * in the planner, it's better to not update relpages either if we can't
! * update reltuples.
*/
! if (vacrelstats->scanned_all)
! vac_update_relstats(onerel,
! vacrelstats->rel_pages, vacrelstats->rel_tuples,
! vacrelstats->hasindex,
! FreezeLimit);
/* report results to the stats collector, too */
pgstat_report_vacuum(RelationGetRelid(onerel),
onerel->rd_rel->relisshared,
! vacrelstats->scanned_all,
! vacrelstats->rel_tuples);
/* and log the action if appropriate */
if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
--- 205,224 ----
FreeSpaceMapVacuum(onerel);
/*
! * Update statistics in pg_class. But don't change relfrozenxid if we
! * skipped any pages.
*/
! vac_update_relstats(onerel,
! vacrelstats->rel_pages, vacrelstats->new_rel_tuples,
! vacrelstats->hasindex,
! (vacrelstats->scanned_pages < vacrelstats->rel_pages) ?
! InvalidTransactionId :
! FreezeLimit);
/* report results to the stats collector, too */
pgstat_report_vacuum(RelationGetRelid(onerel),
onerel->rd_rel->relisshared,
! vacrelstats->new_rel_tuples);
/* and log the action if appropriate */
if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
*************** lazy_vacuum_rel(Relation onerel, VacuumS
*** 239,251 ****
get_namespace_name(RelationGetNamespace(onerel)),
RelationGetRelationName(onerel),
vacrelstats->num_index_scans,
! vacrelstats->pages_removed, vacrelstats->rel_pages,
! vacrelstats->tuples_deleted, vacrelstats->rel_tuples,
pg_rusage_show(&ru0))));
}
-
- if (scanned_all)
- *scanned_all = vacrelstats->scanned_all;
}
/*
--- 235,246 ----
get_namespace_name(RelationGetNamespace(onerel)),
RelationGetRelationName(onerel),
vacrelstats->num_index_scans,
! vacrelstats->pages_removed,
! vacrelstats->rel_pages,
! vacrelstats->tuples_deleted,
! vacrelstats->new_rel_tuples,
pg_rusage_show(&ru0))));
}
}
/*
*************** lazy_scan_heap(Relation onerel, LVRelSta
*** 301,307 ****
HeapTupleData tuple;
char *relname;
BlockNumber empty_pages,
- scanned_pages,
vacuumed_pages;
double num_tuples,
tups_vacuumed,
--- 296,301 ----
*************** lazy_scan_heap(Relation onerel, LVRelSta
*** 321,327 ****
get_namespace_name(RelationGetNamespace(onerel)),
relname)));
! empty_pages = vacuumed_pages = scanned_pages = 0;
num_tuples = tups_vacuumed = nkeep = nunused = 0;
indstats = (IndexBulkDeleteResult **)
--- 315,321 ----
get_namespace_name(RelationGetNamespace(onerel)),
relname)));
! empty_pages = vacuumed_pages = 0;
num_tuples = tups_vacuumed = nkeep = nunused = 0;
indstats = (IndexBulkDeleteResult **)
*************** lazy_scan_heap(Relation onerel, LVRelSta
*** 329,340 ****
--- 323,363 ----
nblocks = RelationGetNumberOfBlocks(onerel);
vacrelstats->rel_pages = nblocks;
+ vacrelstats->scanned_pages = 0;
vacrelstats->nonempty_pages = 0;
vacrelstats->latestRemovedXid = InvalidTransactionId;
lazy_space_alloc(vacrelstats, nblocks);
+ /*
+ * We want to skip pages that don't require vacuuming according to the
+ * visibility map, but only if we've seen a streak of at least
+ * SKIP_PAGES_THRESHOLD pages marked as clean. Since we're reading
+ * sequentially, the OS should be doing readahead for us and there's no
+ * gain in skipping a page now and then. You need a longer run of
+ * consecutive skipped pages before it's worthwhile. Also, skipping even
+ * a single page means that we can't update relfrozenxid, so we only want
+ * to do it if there's a good chance to skip a goodly number of pages.
+ *
+ * Before entering the main loop, look ahead to see if there are at least
+ * SKIP_PAGES_THRESHOLD clean pages at the start of the relation; if so,
+ * we are going to skip at least one page, and we might as well skip the
+ * initial pages too. This extra logic prevents over-weighting these
+ * pages when we estimate the new tuple density in vac_estimate_reltuples.
+ */
all_visible_streak = 0;
+ if (!scan_all && nblocks >= SKIP_PAGES_THRESHOLD)
+ {
+ for (blkno = 0; blkno < SKIP_PAGES_THRESHOLD; blkno++)
+ {
+ if (!visibilitymap_test(onerel, blkno, &vmbuffer))
+ break;
+ all_visible_streak++;
+ }
+ if (all_visible_streak < SKIP_PAGES_THRESHOLD)
+ all_visible_streak = 0;
+ }
+
for (blkno = 0; blkno < nblocks; blkno++)
{
Buffer buf;
*************** lazy_scan_heap(Relation onerel, LVRelSta
*** 351,379 ****
bool all_visible;
bool has_dead_tuples;
- /*
- * Skip pages that don't require vacuuming according to the visibility
- * map. But only if we've seen a streak of at least
- * SKIP_PAGES_THRESHOLD pages marked as clean. Since we're reading
- * sequentially, the OS should be doing readahead for us and there's
- * no gain in skipping a page now and then. You need a longer run of
- * consecutive skipped pages before it's worthwhile. Also, skipping
- * even a single page means that we can't update relfrozenxid or
- * reltuples, so we only want to do it if there's a good chance to
- * skip a goodly number of pages.
- */
if (!scan_all)
{
all_visible_according_to_vm =
visibilitymap_test(onerel, blkno, &vmbuffer);
if (all_visible_according_to_vm)
{
all_visible_streak++;
if (all_visible_streak >= SKIP_PAGES_THRESHOLD)
- {
- vacrelstats->scanned_all = false;
continue;
- }
}
else
all_visible_streak = 0;
--- 374,392 ----
bool all_visible;
bool has_dead_tuples;
if (!scan_all)
{
+ /*
+ * Skip pages that don't require vacuuming according to the
+ * visibility map, as per comment above.
+ */
all_visible_according_to_vm =
visibilitymap_test(onerel, blkno, &vmbuffer);
if (all_visible_according_to_vm)
{
all_visible_streak++;
if (all_visible_streak >= SKIP_PAGES_THRESHOLD)
continue;
}
else
all_visible_streak = 0;
*************** lazy_scan_heap(Relation onerel, LVRelSta
*** 381,387 ****
vacuum_delay_point();
! scanned_pages++;
/*
* If we are close to overrunning the available space for dead-tuple
--- 394,400 ----
vacuum_delay_point();
! vacrelstats->scanned_pages++;
/*
* If we are close to overrunning the available space for dead-tuple
*************** lazy_scan_heap(Relation onerel, LVRelSta
*** 764,772 ****
}
/* save stats for use later */
! vacrelstats->rel_tuples = num_tuples;
vacrelstats->tuples_deleted = tups_vacuumed;
/* If any tuples need to be deleted, perform final vacuum cycle */
/* XXX put a threshold on min number of tuples here? */
if (vacrelstats->num_dead_tuples > 0)
--- 777,791 ----
}
/* save stats for use later */
! vacrelstats->scanned_tuples = num_tuples;
vacrelstats->tuples_deleted = tups_vacuumed;
+ /* now we can compute the new value for pg_class.reltuples */
+ vacrelstats->new_rel_tuples = vac_estimate_reltuples(onerel, false,
+ nblocks,
+ vacrelstats->scanned_pages,
+ num_tuples);
+
/* If any tuples need to be deleted, perform final vacuum cycle */
/* XXX put a threshold on min number of tuples here? */
if (vacrelstats->num_dead_tuples > 0)
*************** lazy_scan_heap(Relation onerel, LVRelSta
*** 805,811 ****
ereport(elevel,
(errmsg("\"%s\": found %.0f removable, %.0f nonremovable row versions in %u out of %u pages",
RelationGetRelationName(onerel),
! tups_vacuumed, num_tuples, scanned_pages, nblocks),
errdetail("%.0f dead row versions cannot be removed yet.\n"
"There were %.0f unused item pointers.\n"
"%u pages are entirely empty.\n"
--- 824,831 ----
ereport(elevel,
(errmsg("\"%s\": found %.0f removable, %.0f nonremovable row versions in %u out of %u pages",
RelationGetRelationName(onerel),
! tups_vacuumed, num_tuples,
! vacrelstats->scanned_pages, nblocks),
errdetail("%.0f dead row versions cannot be removed yet.\n"
"There were %.0f unused item pointers.\n"
"%u pages are entirely empty.\n"
*************** lazy_cleanup_index(Relation indrel,
*** 977,986 ****
ivinfo.index = indrel;
ivinfo.analyze_only = false;
! ivinfo.estimated_count = !vacrelstats->scanned_all;
ivinfo.message_level = elevel;
! /* use rel_tuples only if we scanned all pages, else fall back */
! ivinfo.num_heap_tuples = vacrelstats->scanned_all ? vacrelstats->rel_tuples : vacrelstats->old_rel_tuples;
ivinfo.strategy = vac_strategy;
stats = index_vacuum_cleanup(&ivinfo, stats);
--- 997,1005 ----
ivinfo.index = indrel;
ivinfo.analyze_only = false;
! ivinfo.estimated_count = (vacrelstats->scanned_pages < vacrelstats->rel_pages);
ivinfo.message_level = elevel;
! ivinfo.num_heap_tuples = vacrelstats->new_rel_tuples;
ivinfo.strategy = vac_strategy;
stats = index_vacuum_cleanup(&ivinfo, stats);
*************** lazy_truncate_heap(Relation onerel, LVRe
*** 1041,1048 ****
new_rel_pages = RelationGetNumberOfBlocks(onerel);
if (new_rel_pages != old_rel_pages)
{
! /* might as well use the latest news when we update pg_class stats */
! vacrelstats->rel_pages = new_rel_pages;
UnlockRelation(onerel, AccessExclusiveLock);
return;
}
--- 1060,1072 ----
new_rel_pages = RelationGetNumberOfBlocks(onerel);
if (new_rel_pages != old_rel_pages)
{
! /*
! * Note: we intentionally don't update vacrelstats->rel_pages with
! * the new rel size here. If we did, it would amount to assuming that
! * the new pages are empty, which is unlikely. Leaving the numbers
! * alone amounts to assuming that the new pages have the same tuple
! * density as existing ones, which is less unlikely.
! */
UnlockRelation(onerel, AccessExclusiveLock);
return;
}
*************** lazy_truncate_heap(Relation onerel, LVRe
*** 1076,1082 ****
*/
UnlockRelation(onerel, AccessExclusiveLock);
! /* update statistics */
vacrelstats->rel_pages = new_rel_pages;
vacrelstats->pages_removed = old_rel_pages - new_rel_pages;
--- 1100,1110 ----
*/
UnlockRelation(onerel, AccessExclusiveLock);
! /*
! * Update statistics. Here, it *is* correct to adjust rel_pages without
! * also touching reltuples, since the tuple count wasn't changed by the
! * truncation.
! */
vacrelstats->rel_pages = new_rel_pages;
vacrelstats->pages_removed = old_rel_pages - new_rel_pages;
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 5ed6e8337c11fdd599a0deb219e1cb0285228a88..1d80c311d879d9cf9009621860cda3ab19c6dea9 100644
*** a/src/backend/postmaster/pgstat.c
--- b/src/backend/postmaster/pgstat.c
*************** pgstat_report_autovac(Oid dboid)
*** 1246,1253 ****
* ---------
*/
void
! pgstat_report_vacuum(Oid tableoid, bool shared, bool adopt_counts,
! PgStat_Counter tuples)
{
PgStat_MsgVacuum msg;
--- 1246,1252 ----
* ---------
*/
void
! pgstat_report_vacuum(Oid tableoid, bool shared, PgStat_Counter tuples)
{
PgStat_MsgVacuum msg;
*************** pgstat_report_vacuum(Oid tableoid, bool
*** 1257,1263 ****
pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_VACUUM);
msg.m_databaseid = shared ? InvalidOid : MyDatabaseId;
msg.m_tableoid = tableoid;
- msg.m_adopt_counts = adopt_counts;
msg.m_autovacuum = IsAutoVacuumWorkerProcess();
msg.m_vacuumtime = GetCurrentTimestamp();
msg.m_tuples = tuples;
--- 1256,1261 ----
*************** pgstat_report_vacuum(Oid tableoid, bool
*** 1271,1277 ****
* --------
*/
void
! pgstat_report_analyze(Relation rel, bool adopt_counts,
PgStat_Counter livetuples, PgStat_Counter deadtuples)
{
PgStat_MsgAnalyze msg;
--- 1269,1275 ----
* --------
*/
void
! pgstat_report_analyze(Relation rel,
PgStat_Counter livetuples, PgStat_Counter deadtuples)
{
PgStat_MsgAnalyze msg;
*************** pgstat_report_analyze(Relation rel, bool
*** 1308,1314 ****
pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_ANALYZE);
msg.m_databaseid = rel->rd_rel->relisshared ? InvalidOid : MyDatabaseId;
msg.m_tableoid = RelationGetRelid(rel);
- msg.m_adopt_counts = adopt_counts;
msg.m_autovacuum = IsAutoVacuumWorkerProcess();
msg.m_analyzetime = GetCurrentTimestamp();
msg.m_live_tuples = livetuples;
--- 1306,1311 ----
*************** pgstat_recv_vacuum(PgStat_MsgVacuum *msg
*** 4197,4204 ****
tabentry = pgstat_get_tab_entry(dbentry, msg->m_tableoid, true);
! if (msg->m_adopt_counts)
! tabentry->n_live_tuples = msg->m_tuples;
/* Resetting dead_tuples to 0 is an approximation ... */
tabentry->n_dead_tuples = 0;
--- 4194,4200 ----
tabentry = pgstat_get_tab_entry(dbentry, msg->m_tableoid, true);
! tabentry->n_live_tuples = msg->m_tuples;
/* Resetting dead_tuples to 0 is an approximation ... */
tabentry->n_dead_tuples = 0;
*************** pgstat_recv_analyze(PgStat_MsgAnalyze *m
*** 4233,4243 ****
tabentry = pgstat_get_tab_entry(dbentry, msg->m_tableoid, true);
! if (msg->m_adopt_counts)
! {
! tabentry->n_live_tuples = msg->m_live_tuples;
! tabentry->n_dead_tuples = msg->m_dead_tuples;
! }
/*
* We reset changes_since_analyze to zero, forgetting any changes that
--- 4229,4236 ----
tabentry = pgstat_get_tab_entry(dbentry, msg->m_tableoid, true);
! tabentry->n_live_tuples = msg->m_live_tuples;
! tabentry->n_dead_tuples = msg->m_dead_tuples;
/*
* We reset changes_since_analyze to zero, forgetting any changes that
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 79c9f5d90fb674ca8c778a65ca540ef62bded0af..cfbe0c43924029843f636845d87a09996d706af3 100644
*** a/src/include/commands/vacuum.h
--- b/src/include/commands/vacuum.h
*************** extern void vacuum(VacuumStmt *vacstmt,
*** 142,147 ****
--- 142,151 ----
extern void vac_open_indexes(Relation relation, LOCKMODE lockmode,
int *nindexes, Relation **Irel);
extern void vac_close_indexes(int nindexes, Relation *Irel, LOCKMODE lockmode);
+ extern double vac_estimate_reltuples(Relation relation, bool is_analyze,
+ BlockNumber total_pages,
+ BlockNumber scanned_pages,
+ double scanned_tuples);
extern void vac_update_relstats(Relation relation,
BlockNumber num_pages,
double num_tuples,
*************** extern void vacuum_delay_point(void);
*** 157,166 ****
/* in commands/vacuumlazy.c */
extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
! BufferAccessStrategy bstrategy, bool *scanned_all);
/* in commands/analyze.c */
extern void analyze_rel(Oid relid, VacuumStmt *vacstmt,
! BufferAccessStrategy bstrategy, bool update_reltuples);
#endif /* VACUUM_H */
--- 161,170 ----
/* in commands/vacuumlazy.c */
extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
! BufferAccessStrategy bstrategy);
/* in commands/analyze.c */
extern void analyze_rel(Oid relid, VacuumStmt *vacstmt,
! BufferAccessStrategy bstrategy);
#endif /* VACUUM_H */
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index f04be95b459b2053c66495979b95f0b697a2af13..5446fa04409ebefc31a3a1f282e7dd1224a5d734 100644
*** a/src/include/pgstat.h
--- b/src/include/pgstat.h
*************** typedef struct PgStat_MsgVacuum
*** 322,328 ****
PgStat_MsgHdr m_hdr;
Oid m_databaseid;
Oid m_tableoid;
- bool m_adopt_counts;
bool m_autovacuum;
TimestampTz m_vacuumtime;
PgStat_Counter m_tuples;
--- 322,327 ----
*************** typedef struct PgStat_MsgAnalyze
*** 339,345 ****
PgStat_MsgHdr m_hdr;
Oid m_databaseid;
Oid m_tableoid;
- bool m_adopt_counts;
bool m_autovacuum;
TimestampTz m_analyzetime;
PgStat_Counter m_live_tuples;
--- 338,343 ----
*************** extern void pgstat_reset_shared_counters
*** 706,714 ****
extern void pgstat_reset_single_counter(Oid objectid, PgStat_Single_Reset_Type type);
extern void pgstat_report_autovac(Oid dboid);
! extern void pgstat_report_vacuum(Oid tableoid, bool shared, bool adopt_counts,
PgStat_Counter tuples);
! extern void pgstat_report_analyze(Relation rel, bool adopt_counts,
PgStat_Counter livetuples, PgStat_Counter deadtuples);
extern void pgstat_report_recovery_conflict(int reason);
--- 704,712 ----
extern void pgstat_reset_single_counter(Oid objectid, PgStat_Single_Reset_Type type);
extern void pgstat_report_autovac(Oid dboid);
! extern void pgstat_report_vacuum(Oid tableoid, bool shared,
PgStat_Counter tuples);
! extern void pgstat_report_analyze(Relation rel,
PgStat_Counter livetuples, PgStat_Counter deadtuples);
extern void pgstat_report_recovery_conflict(int reason);
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