database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-08-21 10:42:50 +03:00
Code Activity

Fix VACUUM's reporting of dead-tuple counts to the stats collector.

Browse Source 
Historically, VACUUM has just reported its new_rel_tuples estimate
(the same thing it puts into pg_class.reltuples) to the stats collector.
That number counts both live and dead-but-not-yet-reclaimable tuples.
This behavior may once have been right, but modern versions of the
pgstats code track live and dead tuple counts separately, so putting
the total into n_live_tuples and zero into n_dead_tuples is surely
pretty bogus.  Fix it to report live and dead tuple counts separately.

This doesn't really do much for situations where updating transactions
commit concurrently with a VACUUM scan (possibly causing double-counting or
omission of the tuples they add or delete); but it's clearly an improvement
over what we were doing before.

Hari Babu, reviewed by Amit Kapila
This commit is contained in:
Tom Lane
2014-01-18 19:24:20 -05:00
parent 76e91b38ba
commit 115f414124
3 changed files with 20 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
src/backend/commands/vacuumlazy.c
View File

@@ -106,6 +106,7 @@ typedef struct LVRelStats
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 */
double new_dead_tuples; /* new estimated total # of dead tuples */
BlockNumber pages_removed;
double tuples_deleted;
BlockNumber nonempty_pages; /* actually, last nonempty page + 1 */
@@ -185,6 +186,7 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
BlockNumber new_rel_pages;
double new_rel_tuples;
BlockNumber new_rel_allvisible;
double new_live_tuples;
TransactionId new_frozen_xid;
MultiXactId new_min_multi;
@@ -307,9 +309,14 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
new_min_multi);
/* report results to the stats collector, too */
new_live_tuples = new_rel_tuples - vacrelstats->new_dead_tuples;
if (new_live_tuples < 0)
new_live_tuples = 0; /* just in case */
pgstat_report_vacuum(RelationGetRelid(onerel),
onerel->rd_rel->relisshared,
new_rel_tuples);
new_live_tuples,
vacrelstats->new_dead_tuples);
/* and log the action if appropriate */
if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
@@ -334,7 +341,7 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
ereport(LOG,
(errmsg("automatic vacuum of table \"%s.%s.%s\": index scans: %d\n"
"pages: %d removed, %d remain\n"
"tuples: %.0f removed, %.0f remain\n"
"tuples: %.0f removed, %.0f remain, %.0f are dead but not yet removable\n"
"buffer usage: %d hits, %d misses, %d dirtied\n"
"avg read rate: %.3f MB/s, avg write rate: %.3f MB/s\n"
"system usage: %s",
@@ -346,6 +353,7 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
vacrelstats->rel_pages,
vacrelstats->tuples_deleted,
vacrelstats->new_rel_tuples,
vacrelstats->new_dead_tuples,
VacuumPageHit,
VacuumPageMiss,
VacuumPageDirty,
@@ -1036,6 +1044,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
/* save stats for use later */
vacrelstats->scanned_tuples = num_tuples;
vacrelstats->tuples_deleted = tups_vacuumed;
vacrelstats->new_dead_tuples = nkeep;
/* now we can compute the new value for pg_class.reltuples */
vacrelstats->new_rel_tuples = vac_estimate_reltuples(onerel, false,