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Avoid having autovacuum workers wait for relation locks.

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Waiting for relation locks can lead to starvation - it pins down an
autovacuum worker for as long as the lock is held.  But if we're doing
an anti-wraparound vacuum, then we still wait; maintenance can no longer
be put off.

To assist with troubleshooting, if log_autovacuum_min_duration >= 0,
we log whenever an autovacuum or autoanalyze is skipped for this reason.

Per a gripe by Josh Berkus, and ensuing discussion.
This commit is contained in:
Robert Haas
2011-02-07 22:04:29 -05:00
parent 47082fa875
commit 32896c40ca
5 changed files with 61 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
src/backend/commands/analyze.c
View File

@ -36,6 +36,7 @@
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "utils/acl.h"
@ -148,7 +149,19 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt,
* matter if we ever try to accumulate stats on dead tuples.) If the rel
* has been dropped since we last saw it, we don't need to process it.
*/
onerel = try_relation_open(relid, ShareUpdateExclusiveLock);
if (!(vacstmt->options & VACOPT_NOWAIT))
onerel = try_relation_open(relid, ShareUpdateExclusiveLock);
else if (ConditionalLockRelationOid(relid, ShareUpdateExclusiveLock))
onerel = try_relation_open(relid, NoLock);
else
{
onerel = NULL;
if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
ereport(LOG,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("skipping analyze of \"%s\" --- lock not available",
vacstmt->relation->relname)));
}
if (!onerel)
return;

39
src/backend/commands/vacuum.c
View File

@ -61,7 +61,7 @@ static BufferAccessStrategy vac_strategy;
/* non-export function prototypes */
static List *get_rel_oids(Oid relid, const RangeVar *vacrel);
static void vac_truncate_clog(TransactionId frozenXID);
static void vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast,
static bool vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast,
bool for_wraparound, bool *scanned_all);
@ -226,8 +226,11 @@ vacuum(VacuumStmt *vacstmt, Oid relid, bool do_toast,
bool scanned_all = false;
if (vacstmt->options & VACOPT_VACUUM)
vacuum_rel(relid, vacstmt, do_toast, for_wraparound,
&scanned_all);
{
if (!vacuum_rel(relid, vacstmt, do_toast, for_wraparound,
&scanned_all))
continue;
}
if (vacstmt->options & VACOPT_ANALYZE)
{
@ -764,7 +767,7 @@ vac_truncate_clog(TransactionId frozenXID)
*
* At entry and exit, we are not inside a transaction.
*/
static void
static bool
vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
bool *scanned_all)
{
@ -835,14 +838,29 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
*
* There's a race condition here: the rel may have gone away since the
* last time we saw it. If so, we don't need to vacuum it.
*
* If we've been asked not to wait for the relation lock, acquire it
* first in non-blocking mode, before calling try_relation_open().
*/
onerel = try_relation_open(relid, lmode);
if (!(vacstmt->options & VACOPT_NOWAIT))
onerel = try_relation_open(relid, lmode);
else if (ConditionalLockRelationOid(relid, lmode))
onerel = try_relation_open(relid, NoLock);
else
{
onerel = NULL;
if (IsAutoVacuumWorkerProcess() && Log_autovacuum_min_duration >= 0)
ereport(LOG,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("skipping vacuum of \"%s\" --- lock not available",
vacstmt->relation->relname)));
}
if (!onerel)
{
PopActiveSnapshot();
CommitTransactionCommand();
return;
return false;
}
/*
@ -873,7 +891,7 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
relation_close(onerel, lmode);
PopActiveSnapshot();
CommitTransactionCommand();
return;
return false;
}
/*
@ -890,7 +908,7 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
relation_close(onerel, lmode);
PopActiveSnapshot();
CommitTransactionCommand();
return;
return false;
}
/*
@ -905,7 +923,7 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
relation_close(onerel, lmode);
PopActiveSnapshot();
CommitTransactionCommand();
return;
return false;
}
/*
@ -989,6 +1007,9 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
* Now release the session-level lock on the master table.
*/
UnlockRelationIdForSession(&onerelid, lmode);
/* Report that we really did it. */
return true;
}

14
src/backend/postmaster/autovacuum.c
View File

@ -2671,19 +2671,27 @@ autovacuum_do_vac_analyze(autovac_table *tab,
BufferAccessStrategy bstrategy)
{
VacuumStmt vacstmt;
RangeVar rangevar;
/* Set up command parameters --- use a local variable instead of palloc */
/* Set up command parameters --- use local variables instead of palloc */
MemSet(&vacstmt, 0, sizeof(vacstmt));
MemSet(&rangevar, 0, sizeof(rangevar));
rangevar.schemaname = tab->at_nspname;
rangevar.relname = tab->at_relname;
rangevar.location = -1;
vacstmt.type = T_VacuumStmt;
vacstmt.options = 0;
if (!tab->at_wraparound)
vacstmt.options = VACOPT_NOWAIT;
if (tab->at_dovacuum)
vacstmt.options |= VACOPT_VACUUM;
if (tab->at_doanalyze)
vacstmt.options |= VACOPT_ANALYZE;
vacstmt.freeze_min_age = tab->at_freeze_min_age;
vacstmt.freeze_table_age = tab->at_freeze_table_age;
vacstmt.relation = NULL; /* not used since we pass a relid */
/* we pass the OID, but might need this anyway for an error message */
vacstmt.relation = &rangevar;
vacstmt.va_cols = NIL;
/* Let pgstat know what we're doing */

3
src/include/nodes/parsenodes.h
View File

@ -2332,7 +2332,8 @@ typedef enum VacuumOption
VACOPT_ANALYZE = 1 << 1, /* do ANALYZE */
VACOPT_VERBOSE = 1 << 2, /* print progress info */
VACOPT_FREEZE = 1 << 3, /* FREEZE option */
VACOPT_FULL = 1 << 4 /* FULL (non-concurrent) vacuum */
VACOPT_FULL = 1 << 4, /* FULL (non-concurrent) vacuum */
VACOPT_NOWAIT = 1 << 5
} VacuumOption;
typedef struct VacuumStmt