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

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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
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11
src/backend/postmaster/pgstat.c
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@@ -1327,7 +1327,8 @@ pgstat_report_autovac(Oid dboid)
* ---------
*/
void
pgstat_report_vacuum(Oid tableoid, bool shared, PgStat_Counter tuples)
pgstat_report_vacuum(Oid tableoid, bool shared,
PgStat_Counter livetuples, PgStat_Counter deadtuples)
{
PgStat_MsgVacuum msg;
@@ -1339,7 +1340,8 @@ pgstat_report_vacuum(Oid tableoid, bool shared, PgStat_Counter tuples)
msg.m_tableoid = tableoid;
msg.m_autovacuum = IsAutoVacuumWorkerProcess();
msg.m_vacuumtime = GetCurrentTimestamp();
msg.m_tuples = tuples;
msg.m_live_tuples = livetuples;
msg.m_dead_tuples = deadtuples;
pgstat_send(&msg, sizeof(msg));
}
@@ -4809,9 +4811,8 @@ pgstat_recv_vacuum(PgStat_MsgVacuum *msg, int len)
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;
tabentry->n_live_tuples = msg->m_live_tuples;
tabentry->n_dead_tuples = msg->m_dead_tuples;
if (msg->m_autovacuum)
{