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Commita904abe

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Fix concurrent indexing operations with temporary tables
Attempting to use CREATE INDEX, DROP INDEX or REINDEX with CONCURRENTLYon a temporary relation with ON COMMIT actions triggered unexpectederrors because those operations use multiple transactions internally tocomplete their work. Here is for example one confusing error when usingON COMMIT DELETE ROWS:ERROR: index "foo" already contains dataIssues related to temporary relations and concurrent indexing are fixedin this commit by enforcing the non-concurrent path to be taken fortemporary relations even if using CONCURRENTLY, transparently to theuser. Using a non-concurrent path does not matter in practice as lockscannot be taken on a temporary relation by a session different than theone owning the relation, and the non-concurrent operation is moreeffective.The problem exists with REINDEX since v12 with the introduction ofCONCURRENTLY, and with CREATE/DROP INDEX since CONCURRENTLY exists forthose commands. In all supported versions, this caused only confusingerror messages to be generated. Note that with REINDEX, it was alsopossible to issue a REINDEX CONCURRENTLY for a temporary relation ownedby a different session, leading to a server crash.The idea to enforce transparently the non-concurrent code path fortemporary relations comes originally from Andres Freund.Reported-by: Manuel RiggerAuthor: Michael Paquier, Heikki LinnakangasReviewed-by: Andres Freund, Álvaro Herrera, Heikki LinnakangasDiscussion:https://postgr.es/m/CA+u7OA6gP7YAeCguyseusYcc=uR8+ypjCcgDDCTzjQ+k6S9ksQ@mail.gmail.comBackpatch-through: 9.4
1 parent9b9c5f2 commita904abe

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8 files changed

+235
-13
lines changed

8 files changed

+235
-13
lines changed

‎doc/src/sgml/ref/create_index.sgml‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -129,6 +129,11 @@ CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] <replaceable class=
129129
&mdash; see <xref linkend="sql-createindex-concurrently"
130130
endterm="sql-createindex-concurrently-title"/>.
131131
</para>
132+
<para>
133+
For temporary tables, <command>CREATE INDEX</command> is always
134+
non-concurrent, as no other session can access them, and
135+
non-concurrent index creation is cheaper.
136+
</para>
132137
</listitem>
133138
</varlistentry>
134139

‎doc/src/sgml/ref/drop_index.sgml‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -58,6 +58,11 @@ DROP INDEX [ CONCURRENTLY ] [ IF EXISTS ] <replaceable class="parameter">name</r
5858
performed within a transaction block, but
5959
<command>DROP INDEX CONCURRENTLY</command> cannot.
6060
</para>
61+
<para>
62+
For temporary tables, <command>DROP INDEX</command> is always
63+
non-concurrent, as no other session can access them, and
64+
non-concurrent index drop is cheaper.
65+
</para>
6166
</listitem>
6267
</varlistentry>
6368

‎doc/src/sgml/ref/reindex.sgml‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -166,6 +166,11 @@ REINDEX [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] { IN
166166
&mdash; see <xref linkend="sql-reindex-concurrently"
167167
endterm="sql-reindex-concurrently-title"/>.
168168
</para>
169+
<para>
170+
For temporary tables, <command>REINDEX</command> is always
171+
non-concurrent, as no other session can access them, and
172+
non-concurrent reindex is cheaper.
173+
</para>
169174
</listitem>
170175
</varlistentry>
171176

‎src/backend/catalog/index.c‎

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2016,6 +2016,15 @@ index_drop(Oid indexId, bool concurrent, bool concurrent_lock_mode)
20162016
LOCKTAGheaplocktag;
20172017
LOCKMODElockmode;
20182018

2019+
/*
2020+
* A temporary relation uses a non-concurrent DROP. Other backends can't
2021+
* access a temporary relation, so there's no harm in grabbing a stronger
2022+
* lock (see comments in RemoveRelations), and a non-concurrent DROP is
2023+
* more efficient.
2024+
*/
2025+
Assert(get_rel_persistence(indexId)!=RELPERSISTENCE_TEMP||
2026+
(!concurrent&& !concurrent_lock_mode));
2027+
20192028
/*
20202029
* To drop an index safely, we must grab exclusive lock on its parent
20212030
* table. Exclusive lock on the index alone is insufficient because

‎src/backend/commands/indexcmds.c‎

Lines changed: 53 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -438,6 +438,7 @@ DefineIndex(Oid relationId,
438438
boolskip_build,
439439
boolquiet)
440440
{
441+
boolconcurrent;
441442
char*indexRelationName;
442443
char*accessMethodName;
443444
Oid*typeObjectId;
@@ -485,6 +486,18 @@ DefineIndex(Oid relationId,
485486
GUC_ACTION_SAVE, true,0, false);
486487
}
487488

489+
/*
490+
* Force non-concurrent build on temporary relations, even if CONCURRENTLY
491+
* was requested. Other backends can't access a temporary relation, so
492+
* there's no harm in grabbing a stronger lock, and a non-concurrent DROP
493+
* is more efficient. Do this before any use of the concurrent option is
494+
* done.
495+
*/
496+
if (stmt->concurrent&&get_rel_persistence(relationId)!=RELPERSISTENCE_TEMP)
497+
concurrent= true;
498+
else
499+
concurrent= false;
500+
488501
/*
489502
* Start progress report. If we're building a partition, this was already
490503
* done.
@@ -494,7 +507,7 @@ DefineIndex(Oid relationId,
494507
pgstat_progress_start_command(PROGRESS_COMMAND_CREATE_INDEX,
495508
relationId);
496509
pgstat_progress_update_param(PROGRESS_CREATEIDX_COMMAND,
497-
stmt->concurrent ?
510+
concurrent ?
498511
PROGRESS_CREATEIDX_COMMAND_CREATE_CONCURRENTLY :
499512
PROGRESS_CREATEIDX_COMMAND_CREATE);
500513
}
@@ -547,7 +560,7 @@ DefineIndex(Oid relationId,
547560
* parallel workers under the control of certain particular ambuild
548561
* functions will need to be updated, too.
549562
*/
550-
lockmode=stmt->concurrent ?ShareUpdateExclusiveLock :ShareLock;
563+
lockmode=concurrent ?ShareUpdateExclusiveLock :ShareLock;
551564
rel=table_open(relationId,lockmode);
552565

553566
namespaceId=RelationGetNamespace(rel);
@@ -590,6 +603,12 @@ DefineIndex(Oid relationId,
590603
partitioned=rel->rd_rel->relkind==RELKIND_PARTITIONED_TABLE;
591604
if (partitioned)
592605
{
606+
/*
607+
* Note: we check 'stmt->concurrent' rather than 'concurrent', so that
608+
* the error is thrown also for temporary tables. Seems better to be
609+
* consistent, even though we could do it on temporary table because
610+
* we're not actually doing it concurrently.
611+
*/
593612
if (stmt->concurrent)
594613
ereport(ERROR,
595614
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -781,8 +800,8 @@ DefineIndex(Oid relationId,
781800
NIL,/* expressions, NIL for now */
782801
make_ands_implicit((Expr*)stmt->whereClause),
783802
stmt->unique,
784-
!stmt->concurrent,
785-
stmt->concurrent);
803+
!concurrent,
804+
concurrent);
786805

787806
typeObjectId= (Oid*)palloc(numberOfAttributes*sizeof(Oid));
788807
collationObjectId= (Oid*)palloc(numberOfAttributes*sizeof(Oid));
@@ -944,7 +963,7 @@ DefineIndex(Oid relationId,
944963
* A valid stmt->oldNode implies that we already have a built form of the
945964
* index. The caller should also decline any index build.
946965
*/
947-
Assert(!OidIsValid(stmt->oldNode)|| (skip_build&& !stmt->concurrent));
966+
Assert(!OidIsValid(stmt->oldNode)|| (skip_build&& !concurrent));
948967

949968
/*
950969
* Make the catalog entries for the index, including constraints. This
@@ -955,11 +974,11 @@ DefineIndex(Oid relationId,
955974
flags=constr_flags=0;
956975
if (stmt->isconstraint)
957976
flags |=INDEX_CREATE_ADD_CONSTRAINT;
958-
if (skip_build||stmt->concurrent||partitioned)
977+
if (skip_build||concurrent||partitioned)
959978
flags |=INDEX_CREATE_SKIP_BUILD;
960979
if (stmt->if_not_exists)
961980
flags |=INDEX_CREATE_IF_NOT_EXISTS;
962-
if (stmt->concurrent)
981+
if (concurrent)
963982
flags |=INDEX_CREATE_CONCURRENT;
964983
if (partitioned)
965984
flags |=INDEX_CREATE_PARTITIONED;
@@ -1253,7 +1272,7 @@ DefineIndex(Oid relationId,
12531272
returnaddress;
12541273
}
12551274

1256-
if (!stmt->concurrent)
1275+
if (!concurrent)
12571276
{
12581277
/* Close the heap and we're done, in the non-concurrent case */
12591278
table_close(rel,NoLock);
@@ -2323,6 +2342,11 @@ ReindexIndex(RangeVar *indexRelation, int options, bool concurrent)
23232342
* Find and lock index, and check permissions on table; use callback to
23242343
* obtain lock on table first, to avoid deadlock hazard. The lock level
23252344
* used here must match the index lock obtained in reindex_index().
2345+
*
2346+
* If it's a temporary index, we will perform a non-concurrent reindex,
2347+
* even if CONCURRENTLY was requested. In that case, reindex_index() will
2348+
* upgrade the lock, but that's OK, because other sessions can't hold
2349+
* locks on our temporary table.
23262350
*/
23272351
state.concurrent=concurrent;
23282352
state.locked_table_oid=InvalidOid;
@@ -2347,7 +2371,7 @@ ReindexIndex(RangeVar *indexRelation, int options, bool concurrent)
23472371
persistence=irel->rd_rel->relpersistence;
23482372
index_close(irel,NoLock);
23492373

2350-
if (concurrent)
2374+
if (concurrent&&persistence!=RELPERSISTENCE_TEMP)
23512375
ReindexRelationConcurrently(indOid,options);
23522376
else
23532377
reindex_index(indOid, false,persistence,
@@ -2434,13 +2458,20 @@ ReindexTable(RangeVar *relation, int options, bool concurrent)
24342458
OidheapOid;
24352459
boolresult;
24362460

2437-
/* The lock level used here should match reindex_relation(). */
2461+
/*
2462+
* The lock level used here should match reindex_relation().
2463+
*
2464+
* If it's a temporary table, we will perform a non-concurrent reindex,
2465+
* even if CONCURRENTLY was requested. In that case, reindex_relation()
2466+
* will upgrade the lock, but that's OK, because other sessions can't hold
2467+
* locks on our temporary table.
2468+
*/
24382469
heapOid=RangeVarGetRelidExtended(relation,
24392470
concurrent ?ShareUpdateExclusiveLock :ShareLock,
24402471
0,
24412472
RangeVarCallbackOwnsTable,NULL);
24422473

2443-
if (concurrent)
2474+
if (concurrent&&get_rel_persistence(heapOid)!=RELPERSISTENCE_TEMP)
24442475
{
24452476
result=ReindexRelationConcurrently(heapOid,options);
24462477

@@ -2646,7 +2677,7 @@ ReindexMultipleTables(const char *objectName, ReindexObjectType objectKind,
26462677
/* functions in indexes may want a snapshot set */
26472678
PushActiveSnapshot(GetTransactionSnapshot());
26482679

2649-
if (concurrent)
2680+
if (concurrent&&get_rel_persistence(relid)!=RELPERSISTENCE_TEMP)
26502681
{
26512682
(void)ReindexRelationConcurrently(relid,options);
26522683
/* ReindexRelationConcurrently() does the verbose output */
@@ -2694,6 +2725,12 @@ ReindexMultipleTables(const char *objectName, ReindexObjectType objectKind,
26942725
*
26952726
* Returns true if any indexes have been rebuilt (including toast table's
26962727
* indexes, when relevant), otherwise returns false.
2728+
*
2729+
* NOTE: This cannot be used on temporary relations. A concurrent build would
2730+
* cause issues with ON COMMIT actions triggered by the transactions of the
2731+
* concurrent build. Temporary relations are not subject to concurrent
2732+
* concerns, so there's no need for the more complicated concurrent build,
2733+
* anyway, and a non-concurrent reindex is more efficient.
26972734
*/
26982735
staticbool
26992736
ReindexRelationConcurrently(OidrelationOid,intoptions)
@@ -2937,6 +2974,10 @@ ReindexRelationConcurrently(Oid relationOid, int options)
29372974
heapRel=table_open(indexRel->rd_index->indrelid,
29382975
ShareUpdateExclusiveLock);
29392976

2977+
/* This function shouldn't be called for temporary relations. */
2978+
if (indexRel->rd_rel->relpersistence==RELPERSISTENCE_TEMP)
2979+
elog(ERROR,"cannot reindex a temporary table concurrently");
2980+
29402981
pgstat_progress_start_command(PROGRESS_COMMAND_CREATE_INDEX,
29412982
RelationGetRelid(heapRel));
29422983
pgstat_progress_update_param(PROGRESS_CREATEIDX_COMMAND,

‎src/backend/commands/tablecmds.c‎

Lines changed: 17 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1260,7 +1260,11 @@ RemoveRelations(DropStmt *drop)
12601260
/* DROP CONCURRENTLY uses a weaker lock, and has some restrictions */
12611261
if (drop->concurrent)
12621262
{
1263-
flags |= PERFORM_DELETION_CONCURRENTLY;
1263+
/*
1264+
* Note that for temporary relations this lock may get upgraded
1265+
* later on, but as no other session can access a temporary
1266+
* relation, this is actually fine.
1267+
*/
12641268
lockmode = ShareUpdateExclusiveLock;
12651269
Assert(drop->removeType == OBJECT_INDEX);
12661270
if (list_length(drop->objects) != 1)
@@ -1351,6 +1355,18 @@ RemoveRelations(DropStmt *drop)
13511355
continue;
13521356
}
13531357

1358+
/*
1359+
* Decide if concurrent mode needs to be used here or not. The
1360+
* relation persistence cannot be known without its OID.
1361+
*/
1362+
if (drop->concurrent &&
1363+
get_rel_persistence(relOid) != RELPERSISTENCE_TEMP)
1364+
{
1365+
Assert(list_length(drop->objects) == 1 &&
1366+
drop->removeType == OBJECT_INDEX);
1367+
flags |= PERFORM_DELETION_CONCURRENTLY;
1368+
}
1369+
13541370
/* OK, we're ready to delete this one */
13551371
obj.classId = RelationRelationId;
13561372
obj.objectId = relOid;

‎src/test/regress/expected/create_index.out‎

Lines changed: 74 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1435,6 +1435,31 @@ Indexes:
14351435
"concur_index5" btree (f2) WHERE f1 = 'x'::text
14361436
"std_index" btree (f2)
14371437

1438+
-- Temporary tables with concurrent builds and on-commit actions
1439+
-- CONCURRENTLY used with CREATE INDEX and DROP INDEX is ignored.
1440+
-- PRESERVE ROWS, the default.
1441+
CREATE TEMP TABLE concur_temp (f1 int, f2 text)
1442+
ON COMMIT PRESERVE ROWS;
1443+
INSERT INTO concur_temp VALUES (1, 'foo'), (2, 'bar');
1444+
CREATE INDEX CONCURRENTLY concur_temp_ind ON concur_temp(f1);
1445+
DROP INDEX CONCURRENTLY concur_temp_ind;
1446+
DROP TABLE concur_temp;
1447+
-- ON COMMIT DROP
1448+
BEGIN;
1449+
CREATE TEMP TABLE concur_temp (f1 int, f2 text)
1450+
ON COMMIT DROP;
1451+
INSERT INTO concur_temp VALUES (1, 'foo'), (2, 'bar');
1452+
-- Fails when running in a transaction.
1453+
CREATE INDEX CONCURRENTLY concur_temp_ind ON concur_temp(f1);
1454+
ERROR: CREATE INDEX CONCURRENTLY cannot run inside a transaction block
1455+
COMMIT;
1456+
-- ON COMMIT DELETE ROWS
1457+
CREATE TEMP TABLE concur_temp (f1 int, f2 text)
1458+
ON COMMIT DELETE ROWS;
1459+
INSERT INTO concur_temp VALUES (1, 'foo'), (2, 'bar');
1460+
CREATE INDEX CONCURRENTLY concur_temp_ind ON concur_temp(f1);
1461+
DROP INDEX CONCURRENTLY concur_temp_ind;
1462+
DROP TABLE concur_temp;
14381463
--
14391464
-- Try some concurrent index drops
14401465
--
@@ -2418,6 +2443,55 @@ SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
24182443
(1 row)
24192444

24202445
DROP TABLE concur_exprs_tab;
2446+
-- Temporary tables and on-commit actions, where CONCURRENTLY is ignored.
2447+
-- ON COMMIT PRESERVE ROWS, the default.
2448+
CREATE TEMP TABLE concur_temp_tab_1 (c1 int, c2 text)
2449+
ON COMMIT PRESERVE ROWS;
2450+
INSERT INTO concur_temp_tab_1 VALUES (1, 'foo'), (2, 'bar');
2451+
CREATE INDEX concur_temp_ind_1 ON concur_temp_tab_1(c2);
2452+
REINDEX TABLE CONCURRENTLY concur_temp_tab_1;
2453+
REINDEX INDEX CONCURRENTLY concur_temp_ind_1;
2454+
-- Still fails in transaction blocks
2455+
BEGIN;
2456+
REINDEX INDEX CONCURRENTLY concur_temp_ind_1;
2457+
ERROR: REINDEX CONCURRENTLY cannot run inside a transaction block
2458+
COMMIT;
2459+
-- ON COMMIT DELETE ROWS
2460+
CREATE TEMP TABLE concur_temp_tab_2 (c1 int, c2 text)
2461+
ON COMMIT DELETE ROWS;
2462+
CREATE INDEX concur_temp_ind_2 ON concur_temp_tab_2(c2);
2463+
REINDEX TABLE CONCURRENTLY concur_temp_tab_2;
2464+
REINDEX INDEX CONCURRENTLY concur_temp_ind_2;
2465+
-- ON COMMIT DROP
2466+
BEGIN;
2467+
CREATE TEMP TABLE concur_temp_tab_3 (c1 int, c2 text)
2468+
ON COMMIT PRESERVE ROWS;
2469+
INSERT INTO concur_temp_tab_3 VALUES (1, 'foo'), (2, 'bar');
2470+
CREATE INDEX concur_temp_ind_3 ON concur_temp_tab_3(c2);
2471+
-- Fails when running in a transaction
2472+
REINDEX INDEX CONCURRENTLY concur_temp_ind_3;
2473+
ERROR: REINDEX CONCURRENTLY cannot run inside a transaction block
2474+
COMMIT;
2475+
-- REINDEX SCHEMA processes all temporary relations
2476+
CREATE TABLE reindex_temp_before AS
2477+
SELECT oid, relname, relfilenode, relkind, reltoastrelid
2478+
FROM pg_class
2479+
WHERE relname IN ('concur_temp_ind_1', 'concur_temp_ind_2');
2480+
SELECT pg_my_temp_schema()::regnamespace as temp_schema_name \gset
2481+
REINDEX SCHEMA CONCURRENTLY :temp_schema_name;
2482+
SELECT b.relname,
2483+
b.relkind,
2484+
CASE WHEN a.relfilenode = b.relfilenode THEN 'relfilenode is unchanged'
2485+
ELSE 'relfilenode has changed' END
2486+
FROM reindex_temp_before b JOIN pg_class a ON b.oid = a.oid
2487+
ORDER BY 1;
2488+
relname | relkind | case
2489+
-------------------+---------+-------------------------
2490+
concur_temp_ind_1 | i | relfilenode has changed
2491+
concur_temp_ind_2 | i | relfilenode has changed
2492+
(2 rows)
2493+
2494+
DROP TABLE concur_temp_tab_1, concur_temp_tab_2, reindex_temp_before;
24212495
--
24222496
-- REINDEX SCHEMA
24232497
--

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