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Commit32896c4

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Avoid having autovacuum workers wait for relation locks.
Waiting for relation locks can lead to starvation - it pins down anautovacuum worker for as long as the lock is held. But if we're doingan anti-wraparound vacuum, then we still wait; maintenance can no longerbe 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.
1 parent47082fa commit32896c4

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5 files changed

+61
-15
lines changed

5 files changed

+61
-15
lines changed

‎doc/src/sgml/config.sgml

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -4080,7 +4080,10 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
40804080
all autovacuum actions. Minus-one (the default) disables logging
40814081
autovacuum actions. For example, if you set this to
40824082
<literal>250ms</literal> then all automatic vacuums and analyzes that run
4083-
250ms or longer will be logged. Enabling this parameter can be helpful
4083+
250ms or longer will be logged. In addition, when this parameter is
4084+
set to any value other than <literal>-1</literal>, a message will be
4085+
logged if an autovacuum action is skipped due to the existence of a
4086+
conflicting lock. Enabling this parameter can be helpful
40844087
in tracking autovacuum activity. This setting can only be set in
40854088
the <filename>postgresql.conf</> file or on the server command line.
40864089
</para>

‎src/backend/commands/analyze.c

Lines changed: 14 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -36,6 +36,7 @@
3636
#include"pgstat.h"
3737
#include"postmaster/autovacuum.h"
3838
#include"storage/bufmgr.h"
39+
#include"storage/lmgr.h"
3940
#include"storage/proc.h"
4041
#include"storage/procarray.h"
4142
#include"utils/acl.h"
@@ -148,7 +149,19 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt,
148149
* matter if we ever try to accumulate stats on dead tuples.) If the rel
149150
* has been dropped since we last saw it, we don't need to process it.
150151
*/
151-
onerel=try_relation_open(relid,ShareUpdateExclusiveLock);
152+
if (!(vacstmt->options&VACOPT_NOWAIT))
153+
onerel=try_relation_open(relid,ShareUpdateExclusiveLock);
154+
elseif (ConditionalLockRelationOid(relid,ShareUpdateExclusiveLock))
155+
onerel=try_relation_open(relid,NoLock);
156+
else
157+
{
158+
onerel=NULL;
159+
if (IsAutoVacuumWorkerProcess()&&Log_autovacuum_min_duration >=0)
160+
ereport(LOG,
161+
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
162+
errmsg("skipping analyze of \"%s\" --- lock not available",
163+
vacstmt->relation->relname)));
164+
}
152165
if (!onerel)
153166
return;
154167

‎src/backend/commands/vacuum.c

Lines changed: 30 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -61,7 +61,7 @@ static BufferAccessStrategy vac_strategy;
6161
/* non-export function prototypes */
6262
staticList*get_rel_oids(Oidrelid,constRangeVar*vacrel);
6363
staticvoidvac_truncate_clog(TransactionIdfrozenXID);
64-
staticvoidvacuum_rel(Oidrelid,VacuumStmt*vacstmt,booldo_toast,
64+
staticboolvacuum_rel(Oidrelid,VacuumStmt*vacstmt,booldo_toast,
6565
boolfor_wraparound,bool*scanned_all);
6666

6767

@@ -226,8 +226,11 @@ vacuum(VacuumStmt *vacstmt, Oid relid, bool do_toast,
226226
boolscanned_all= false;
227227

228228
if (vacstmt->options&VACOPT_VACUUM)
229-
vacuum_rel(relid,vacstmt,do_toast,for_wraparound,
230-
&scanned_all);
229+
{
230+
if (!vacuum_rel(relid,vacstmt,do_toast,for_wraparound,
231+
&scanned_all))
232+
continue;
233+
}
231234

232235
if (vacstmt->options&VACOPT_ANALYZE)
233236
{
@@ -764,7 +767,7 @@ vac_truncate_clog(TransactionId frozenXID)
764767
*
765768
*At entry and exit, we are not inside a transaction.
766769
*/
767-
staticvoid
770+
staticbool
768771
vacuum_rel(Oidrelid,VacuumStmt*vacstmt,booldo_toast,boolfor_wraparound,
769772
bool*scanned_all)
770773
{
@@ -835,14 +838,29 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
835838
*
836839
* There's a race condition here: the rel may have gone away since the
837840
* last time we saw it. If so, we don't need to vacuum it.
841+
*
842+
* If we've been asked not to wait for the relation lock, acquire it
843+
* first in non-blocking mode, before calling try_relation_open().
838844
*/
839-
onerel=try_relation_open(relid,lmode);
845+
if (!(vacstmt->options&VACOPT_NOWAIT))
846+
onerel=try_relation_open(relid,lmode);
847+
elseif (ConditionalLockRelationOid(relid,lmode))
848+
onerel=try_relation_open(relid,NoLock);
849+
else
850+
{
851+
onerel=NULL;
852+
if (IsAutoVacuumWorkerProcess()&&Log_autovacuum_min_duration >=0)
853+
ereport(LOG,
854+
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
855+
errmsg("skipping vacuum of \"%s\" --- lock not available",
856+
vacstmt->relation->relname)));
857+
}
840858

841859
if (!onerel)
842860
{
843861
PopActiveSnapshot();
844862
CommitTransactionCommand();
845-
return;
863+
return false;
846864
}
847865

848866
/*
@@ -873,7 +891,7 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
873891
relation_close(onerel,lmode);
874892
PopActiveSnapshot();
875893
CommitTransactionCommand();
876-
return;
894+
return false;
877895
}
878896

879897
/*
@@ -890,7 +908,7 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
890908
relation_close(onerel,lmode);
891909
PopActiveSnapshot();
892910
CommitTransactionCommand();
893-
return;
911+
return false;
894912
}
895913

896914
/*
@@ -905,7 +923,7 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
905923
relation_close(onerel,lmode);
906924
PopActiveSnapshot();
907925
CommitTransactionCommand();
908-
return;
926+
return false;
909927
}
910928

911929
/*
@@ -989,6 +1007,9 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
9891007
* Now release the session-level lock on the master table.
9901008
*/
9911009
UnlockRelationIdForSession(&onerelid,lmode);
1010+
1011+
/* Report that we really did it. */
1012+
return true;
9921013
}
9931014

9941015

‎src/backend/postmaster/autovacuum.c

Lines changed: 11 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2671,19 +2671,27 @@ autovacuum_do_vac_analyze(autovac_table *tab,
26712671
BufferAccessStrategybstrategy)
26722672
{
26732673
VacuumStmtvacstmt;
2674+
RangeVarrangevar;
26742675

2675-
/* Set up command parameters --- usealocalvariable instead of palloc */
2676+
/* Set up command parameters --- use localvariables instead of palloc */
26762677
MemSet(&vacstmt,0,sizeof(vacstmt));
2678+
MemSet(&rangevar,0,sizeof(rangevar));
2679+
2680+
rangevar.schemaname=tab->at_nspname;
2681+
rangevar.relname=tab->at_relname;
2682+
rangevar.location=-1;
26772683

26782684
vacstmt.type=T_VacuumStmt;
2679-
vacstmt.options=0;
2685+
if (!tab->at_wraparound)
2686+
vacstmt.options=VACOPT_NOWAIT;
26802687
if (tab->at_dovacuum)
26812688
vacstmt.options |=VACOPT_VACUUM;
26822689
if (tab->at_doanalyze)
26832690
vacstmt.options |=VACOPT_ANALYZE;
26842691
vacstmt.freeze_min_age=tab->at_freeze_min_age;
26852692
vacstmt.freeze_table_age=tab->at_freeze_table_age;
2686-
vacstmt.relation=NULL;/* not used since we pass a relid */
2693+
/* we pass the OID, but might need this anyway for an error message */
2694+
vacstmt.relation=&rangevar;
26872695
vacstmt.va_cols=NIL;
26882696

26892697
/* Let pgstat know what we're doing */

‎src/include/nodes/parsenodes.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2332,7 +2332,8 @@ typedef enum VacuumOption
23322332
VACOPT_ANALYZE=1 <<1,/* do ANALYZE */
23332333
VACOPT_VERBOSE=1 <<2,/* print progress info */
23342334
VACOPT_FREEZE=1 <<3,/* FREEZE option */
2335-
VACOPT_FULL=1 <<4/* FULL (non-concurrent) vacuum */
2335+
VACOPT_FULL=1 <<4,/* FULL (non-concurrent) vacuum */
2336+
VACOPT_NOWAIT=1 <<5
23362337
}VacuumOption;
23372338

23382339
typedefstructVacuumStmt

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