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Commitd2af5f8

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committed
Adjust index locking rules as per my proposal of earlier today. You
now are supposed to take some kind of lock on an index whenever youare going to access the index contents, rather than relying only on alock on the parent table.
1 parentd674884 commitd2af5f8

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7 files changed

+74
-46
lines changed

7 files changed

+74
-46
lines changed

‎src/backend/access/heap/tuptoaster.c‎

Lines changed: 5 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.45 2004/08/29 05:06:40 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.46 2004/09/30 23:21:06 tgl Exp $
1212
*
1313
*
1414
* INTERFACE ROUTINES
@@ -1007,11 +1007,13 @@ toast_save_datum(Relation rel, Datum value)
10071007
data_todo=VARATT_SIZE(value)-VARHDRSZ;
10081008

10091009
/*
1010-
* Open the toast relation
1010+
* Open the toast relation. We must explicitly lock the toast index
1011+
* because we aren't using an index scan here.
10111012
*/
10121013
toastrel=heap_open(rel->rd_rel->reltoastrelid,RowExclusiveLock);
10131014
toasttupDesc=toastrel->rd_att;
10141015
toastidx=index_open(toastrel->rd_rel->reltoastidxid);
1016+
LockRelation(toastidx,RowExclusiveLock);
10151017

10161018
/*
10171019
* Split up the item into chunks
@@ -1065,6 +1067,7 @@ toast_save_datum(Relation rel, Datum value)
10651067
/*
10661068
* Done - close toast relation and return the reference
10671069
*/
1070+
UnlockRelation(toastidx,RowExclusiveLock);
10681071
index_close(toastidx);
10691072
heap_close(toastrel,RowExclusiveLock);
10701073

‎src/backend/access/index/indexam.c‎

Lines changed: 10 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/index/indexam.c,v 1.74 2004/08/29 04:12:20 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/index/indexam.c,v 1.75 2004/09/30 23:21:14 tgl Exp $
1212
*
1313
* INTERFACE ROUTINES
1414
*index_open- open an index relation by relation OID
@@ -112,10 +112,15 @@
112112
/* ----------------
113113
*index_open - open an index relation by relation OID
114114
*
115-
*Note: we acquire no lock on the index.An AccessShareLock is
116-
*acquired by index_beginscan (and released by index_endscan).
117-
*Generally, the caller should already hold some type of lock on
118-
*the parent relation to ensure that the index doesn't disappear.
115+
*Note: we acquire no lock on the index. A lock is not needed when
116+
*simply examining the index reldesc; the index's schema information
117+
*is considered to be protected by the lock that the caller had better
118+
*be holding on the parent relation. Some type of lock should be
119+
*obtained on the index before physically accessing it, however.
120+
*This is handled automatically for most uses by index_beginscan
121+
*and index_endscan for scan cases, or by ExecOpenIndices and
122+
*ExecCloseIndices for update cases. Other callers will need to
123+
*obtain their own locks.
119124
*
120125
*This is a convenience routine adapted for indexscan use.
121126
*Some callers may prefer to use relation_open directly.

‎src/backend/commands/analyze.c‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.76 2004/08/29 05:06:41 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.77 2004/09/30 23:21:19 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -243,7 +243,7 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt)
243243
* if there was an explicit column list in the ANALYZE command,
244244
* however.
245245
*/
246-
vac_open_indexes(onerel,&nindexes,&Irel);
246+
vac_open_indexes(onerel,AccessShareLock,&nindexes,&Irel);
247247
hasindex= (nindexes>0);
248248
indexdata=NULL;
249249
analyzableindex= false;
@@ -310,7 +310,7 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt)
310310
*/
311311
if (attr_cnt <=0&& !analyzableindex)
312312
{
313-
vac_close_indexes(nindexes,Irel);
313+
vac_close_indexes(nindexes,Irel,AccessShareLock);
314314
relation_close(onerel,AccessShareLock);
315315
return;
316316
}
@@ -427,7 +427,7 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt)
427427
}
428428

429429
/* Done with indexes */
430-
vac_close_indexes(nindexes,Irel);
430+
vac_close_indexes(nindexes,Irel,NoLock);
431431

432432
/*
433433
* Close source relation now, but keep lock so that no one deletes it

‎src/backend/commands/vacuum.c‎

Lines changed: 27 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
*
1414
*
1515
* IDENTIFICATION
16-
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.291 2004/09/13 20:06:29 tgl Exp $
16+
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.292 2004/09/30 23:21:19 tgl Exp $
1717
*
1818
*-------------------------------------------------------------------------
1919
*/
@@ -1062,7 +1062,7 @@ full_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
10621062
scan_heap(vacrelstats,onerel,&vacuum_pages,&fraged_pages);
10631063

10641064
/* Now open all indexes of the relation */
1065-
vac_open_indexes(onerel,&nindexes,&Irel);
1065+
vac_open_indexes(onerel,AccessExclusiveLock,&nindexes,&Irel);
10661066
if (nindexes>0)
10671067
vacrelstats->hasindex= true;
10681068

@@ -1088,11 +1088,11 @@ full_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
10881088
/* Try to shrink heap */
10891089
repair_frag(vacrelstats,onerel,&vacuum_pages,&fraged_pages,
10901090
nindexes,Irel);
1091-
vac_close_indexes(nindexes,Irel);
1091+
vac_close_indexes(nindexes,Irel,NoLock);
10921092
}
10931093
else
10941094
{
1095-
vac_close_indexes(nindexes,Irel);
1095+
vac_close_indexes(nindexes,Irel,NoLock);
10961096
if (vacuum_pages.num_pages>0)
10971097
{
10981098
/* Clean pages from vacuum_pages list */
@@ -3210,8 +3210,14 @@ vac_cmp_vtlinks(const void *left, const void *right)
32103210
}
32113211

32123212

3213+
/*
3214+
* Open all the indexes of the given relation, obtaining the specified kind
3215+
* of lock on each. Return an array of Relation pointers for the indexes
3216+
* into *Irel, and the number of indexes into *nindexes.
3217+
*/
32133218
void
3214-
vac_open_indexes(Relationrelation,int*nindexes,Relation**Irel)
3219+
vac_open_indexes(Relationrelation,LOCKMODElockmode,
3220+
int*nindexes,Relation**Irel)
32153221
{
32163222
List*indexoidlist;
32173223
ListCell*indexoidscan;
@@ -3230,23 +3236,34 @@ vac_open_indexes(Relation relation, int *nindexes, Relation **Irel)
32303236
foreach(indexoidscan,indexoidlist)
32313237
{
32323238
Oidindexoid=lfirst_oid(indexoidscan);
3239+
Relationind;
32333240

3234-
(*Irel)[i]=index_open(indexoid);
3235-
i++;
3241+
ind=index_open(indexoid);
3242+
(*Irel)[i++]=ind;
3243+
LockRelation(ind,lockmode);
32363244
}
32373245

32383246
list_free(indexoidlist);
32393247
}
32403248

3241-
3249+
/*
3250+
* Release the resources acquired by vac_open_indexes. Optionally release
3251+
* the locks (say NoLock to keep 'em).
3252+
*/
32423253
void
3243-
vac_close_indexes(intnindexes,Relation*Irel)
3254+
vac_close_indexes(intnindexes,Relation*Irel,LOCKMODElockmode)
32443255
{
32453256
if (Irel==NULL)
32463257
return;
32473258

32483259
while (nindexes--)
3249-
index_close(Irel[nindexes]);
3260+
{
3261+
Relationind=Irel[nindexes];
3262+
3263+
if (lockmode!=NoLock)
3264+
UnlockRelation(ind,lockmode);
3265+
index_close(ind);
3266+
}
32503267
pfree(Irel);
32513268
}
32523269

‎src/backend/commands/vacuumlazy.c‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -31,7 +31,7 @@
3131
*
3232
*
3333
* IDENTIFICATION
34-
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.45 2004/08/29 05:06:41 momjian Exp $
34+
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.46 2004/09/30 23:21:19 tgl Exp $
3535
*
3636
*-------------------------------------------------------------------------
3737
*/
@@ -145,14 +145,14 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
145145
vacrelstats->threshold=GetAvgFSMRequestSize(&onerel->rd_node);
146146

147147
/* Open all indexes of the relation */
148-
vac_open_indexes(onerel,&nindexes,&Irel);
148+
vac_open_indexes(onerel,ShareUpdateExclusiveLock,&nindexes,&Irel);
149149
hasindex= (nindexes>0);
150150

151151
/* Do the vacuuming */
152152
lazy_scan_heap(onerel,vacrelstats,Irel,nindexes);
153153

154154
/* Done with indexes */
155-
vac_close_indexes(nindexes,Irel);
155+
vac_close_indexes(nindexes,Irel,NoLock);
156156

157157
/*
158158
* Optionally truncate the relation.

‎src/backend/executor/execUtils.c‎

Lines changed: 21 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.115 2004/09/11 18:28:34 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.116 2004/09/30 23:21:23 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -682,28 +682,29 @@ ExecOpenIndices(ResultRelInfo *resultRelInfo)
682682
IndexInfo*ii;
683683

684684
/*
685-
* Open (and lock, if necessary) the index relation
685+
* Open and lock the index relation
686+
*
687+
* If the index AM supports concurrent updates, obtain RowExclusiveLock
688+
* to signify that we are updating the index. This locks out only
689+
* operations that need exclusive access, such as relocating the index
690+
* to a new tablespace.
686691
*
687692
* If the index AM is not safe for concurrent updates, obtain an
688693
* exclusive lock on the index to lock out other updaters as well
689-
* as readers (index_beginscan places AccessShareLock). We will
690-
* release this lock in ExecCloseIndices.
691-
*
692-
* If the index AM supports concurrent updates, we obtain no lock
693-
* here at all, which is a tad weird, but safe since any critical
694-
* operation on the index (like deleting it) will acquire
695-
* exclusive lock on the parent table.Perhaps someday we should
696-
* acquire RowExclusiveLock on the index here?
694+
* as readers (index_beginscan places AccessShareLock).
697695
*
698696
* If there are multiple not-concurrent-safe indexes, all backends
699-
* must lock the indexes in the same order or we will get
700-
* deadlocks here during concurrent updates. This is guaranteed
701-
* by RelationGetIndexList(), which promises to return the index
702-
* list in OID order.
697+
* must lock the indexes in the same order or we will get deadlocks
698+
* here. This is guaranteed by RelationGetIndexList(), which promises
699+
* to return the index list in OID order.
700+
*
701+
* The locks will be released in ExecCloseIndices.
703702
*/
704703
indexDesc=index_open(indexOid);
705704

706-
if (!indexDesc->rd_am->amconcurrent)
705+
if (indexDesc->rd_am->amconcurrent)
706+
LockRelation(indexDesc,RowExclusiveLock);
707+
else
707708
LockRelation(indexDesc,AccessExclusiveLock);
708709

709710
/* extract index key information from the index's pg_index info */
@@ -736,10 +737,12 @@ ExecCloseIndices(ResultRelInfo *resultRelInfo)
736737
for (i=0;i<numIndices;i++)
737738
{
738739
if (indexDescs[i]==NULL)
739-
continue;
740+
continue;/* shouldn't happen? */
740741

741-
/* Drop lock, if one was acquired by ExecOpenIndices */
742-
if (!indexDescs[i]->rd_am->amconcurrent)
742+
/* Drop lock acquired by ExecOpenIndices */
743+
if (indexDescs[i]->rd_am->amconcurrent)
744+
UnlockRelation(indexDescs[i],RowExclusiveLock);
745+
else
743746
UnlockRelation(indexDescs[i],AccessExclusiveLock);
744747

745748
index_close(indexDescs[i]);

‎src/include/commands/vacuum.h‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.57 2004/08/29 05:06:56 momjian Exp $
10+
* $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.58 2004/09/30 23:21:26 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -126,9 +126,9 @@ extern DLLIMPORT int default_statistics_target; /* DLLIMPORT for PostGIS */
126126

127127
/* in commands/vacuum.c */
128128
externvoidvacuum(VacuumStmt*vacstmt);
129-
externvoidvac_open_indexes(Relationrelation,int*nindexes,
130-
Relation**Irel);
131-
externvoidvac_close_indexes(intnindexes,Relation*Irel);
129+
externvoidvac_open_indexes(Relationrelation,LOCKMODElockmode,
130+
int*nindexes,Relation**Irel);
131+
externvoidvac_close_indexes(intnindexes,Relation*Irel,LOCKMODElockmode);
132132
externvoidvac_update_relstats(Oidrelid,
133133
BlockNumbernum_pages,
134134
doublenum_tuples,

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