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Commit817a1b8

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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 parent21fdfd0 commit817a1b8

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8 files changed

+235
-13
lines changed

8 files changed

+235
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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
@@ -162,6 +162,11 @@ REINDEX [ ( VERBOSE ) ] { INDEX | TABLE | SCHEMA | DATABASE | SYSTEM } [ CONCURR
162162
&mdash; see <xref linkend="sql-reindex-concurrently"
163163
endterm="sql-reindex-concurrently-title"/>.
164164
</para>
165+
<para>
166+
For temporary tables, <command>REINDEX</command> is always
167+
non-concurrent, as no other session can access them, and
168+
non-concurrent reindex is cheaper.
169+
</para>
165170
</listitem>
166171
</varlistentry>
167172

‎src/backend/catalog/index.c

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2017,6 +2017,15 @@ index_drop(Oid indexId, bool concurrent, bool concurrent_lock_mode)
20172017
LOCKTAGheaplocktag;
20182018
LOCKMODElockmode;
20192019

2020+
/*
2021+
* A temporary relation uses a non-concurrent DROP. Other backends can't
2022+
* access a temporary relation, so there's no harm in grabbing a stronger
2023+
* lock (see comments in RemoveRelations), and a non-concurrent DROP is
2024+
* more efficient.
2025+
*/
2026+
Assert(get_rel_persistence(indexId)!=RELPERSISTENCE_TEMP||
2027+
(!concurrent&& !concurrent_lock_mode));
2028+
20202029
/*
20212030
* To drop an index safely, we must grab exclusive lock on its parent
20222031
* 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;
@@ -1256,7 +1275,7 @@ DefineIndex(Oid relationId,
12561275
returnaddress;
12571276
}
12581277

1259-
if (!stmt->concurrent)
1278+
if (!concurrent)
12601279
{
12611280
/* Close the heap and we're done, in the non-concurrent case */
12621281
table_close(rel,NoLock);
@@ -2326,6 +2345,11 @@ ReindexIndex(RangeVar *indexRelation, int options, bool concurrent)
23262345
* Find and lock index, and check permissions on table; use callback to
23272346
* obtain lock on table first, to avoid deadlock hazard. The lock level
23282347
* used here must match the index lock obtained in reindex_index().
2348+
*
2349+
* If it's a temporary index, we will perform a non-concurrent reindex,
2350+
* even if CONCURRENTLY was requested. In that case, reindex_index() will
2351+
* upgrade the lock, but that's OK, because other sessions can't hold
2352+
* locks on our temporary table.
23292353
*/
23302354
state.concurrent=concurrent;
23312355
state.locked_table_oid=InvalidOid;
@@ -2350,7 +2374,7 @@ ReindexIndex(RangeVar *indexRelation, int options, bool concurrent)
23502374
persistence=irel->rd_rel->relpersistence;
23512375
index_close(irel,NoLock);
23522376

2353-
if (concurrent)
2377+
if (concurrent&&persistence!=RELPERSISTENCE_TEMP)
23542378
ReindexRelationConcurrently(indOid,options);
23552379
else
23562380
reindex_index(indOid, false,persistence,
@@ -2437,13 +2461,20 @@ ReindexTable(RangeVar *relation, int options, bool concurrent)
24372461
OidheapOid;
24382462
boolresult;
24392463

2440-
/* The lock level used here should match reindex_relation(). */
2464+
/*
2465+
* The lock level used here should match reindex_relation().
2466+
*
2467+
* If it's a temporary table, we will perform a non-concurrent reindex,
2468+
* even if CONCURRENTLY was requested. In that case, reindex_relation()
2469+
* will upgrade the lock, but that's OK, because other sessions can't hold
2470+
* locks on our temporary table.
2471+
*/
24412472
heapOid=RangeVarGetRelidExtended(relation,
24422473
concurrent ?ShareUpdateExclusiveLock :ShareLock,
24432474
0,
24442475
RangeVarCallbackOwnsTable,NULL);
24452476

2446-
if (concurrent)
2477+
if (concurrent&&get_rel_persistence(heapOid)!=RELPERSISTENCE_TEMP)
24472478
{
24482479
result=ReindexRelationConcurrently(heapOid,options);
24492480

@@ -2649,7 +2680,7 @@ ReindexMultipleTables(const char *objectName, ReindexObjectType objectKind,
26492680
/* functions in indexes may want a snapshot set */
26502681
PushActiveSnapshot(GetTransactionSnapshot());
26512682

2652-
if (concurrent)
2683+
if (concurrent&&get_rel_persistence(relid)!=RELPERSISTENCE_TEMP)
26532684
{
26542685
(void)ReindexRelationConcurrently(relid,options);
26552686
/* ReindexRelationConcurrently() does the verbose output */
@@ -2697,6 +2728,12 @@ ReindexMultipleTables(const char *objectName, ReindexObjectType objectKind,
26972728
*
26982729
* Returns true if any indexes have been rebuilt (including toast table's
26992730
* indexes, when relevant), otherwise returns false.
2731+
*
2732+
* NOTE: This cannot be used on temporary relations. A concurrent build would
2733+
* cause issues with ON COMMIT actions triggered by the transactions of the
2734+
* concurrent build. Temporary relations are not subject to concurrent
2735+
* concerns, so there's no need for the more complicated concurrent build,
2736+
* anyway, and a non-concurrent reindex is more efficient.
27002737
*/
27012738
staticbool
27022739
ReindexRelationConcurrently(OidrelationOid,intoptions)
@@ -2940,6 +2977,10 @@ ReindexRelationConcurrently(Oid relationOid, int options)
29402977
heapRel=table_open(indexRel->rd_index->indrelid,
29412978
ShareUpdateExclusiveLock);
29422979

2980+
/* This function shouldn't be called for temporary relations. */
2981+
if (indexRel->rd_rel->relpersistence==RELPERSISTENCE_TEMP)
2982+
elog(ERROR,"cannot reindex a temporary table concurrently");
2983+
29432984
pgstat_progress_start_command(PROGRESS_COMMAND_CREATE_INDEX,
29442985
RelationGetRelid(heapRel));
29452986
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
@@ -1235,7 +1235,11 @@ RemoveRelations(DropStmt *drop)
12351235
/* DROP CONCURRENTLY uses a weaker lock, and has some restrictions */
12361236
if (drop->concurrent)
12371237
{
1238-
flags |= PERFORM_DELETION_CONCURRENTLY;
1238+
/*
1239+
* Note that for temporary relations this lock may get upgraded
1240+
* later on, but as no other session can access a temporary
1241+
* relation, this is actually fine.
1242+
*/
12391243
lockmode = ShareUpdateExclusiveLock;
12401244
Assert(drop->removeType == OBJECT_INDEX);
12411245
if (list_length(drop->objects) != 1)
@@ -1326,6 +1330,18 @@ RemoveRelations(DropStmt *drop)
13261330
continue;
13271331
}
13281332

1333+
/*
1334+
* Decide if concurrent mode needs to be used here or not. The
1335+
* relation persistence cannot be known without its OID.
1336+
*/
1337+
if (drop->concurrent &&
1338+
get_rel_persistence(relOid) != RELPERSISTENCE_TEMP)
1339+
{
1340+
Assert(list_length(drop->objects) == 1 &&
1341+
drop->removeType == OBJECT_INDEX);
1342+
flags |= PERFORM_DELETION_CONCURRENTLY;
1343+
}
1344+
13291345
/* OK, we're ready to delete this one */
13301346
obj.classId = RelationRelationId;
13311347
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
--
@@ -2405,6 +2430,55 @@ SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
24052430
(1 row)
24062431

24072432
DROP TABLE concur_exprs_tab;
2433+
-- Temporary tables and on-commit actions, where CONCURRENTLY is ignored.
2434+
-- ON COMMIT PRESERVE ROWS, the default.
2435+
CREATE TEMP TABLE concur_temp_tab_1 (c1 int, c2 text)
2436+
ON COMMIT PRESERVE ROWS;
2437+
INSERT INTO concur_temp_tab_1 VALUES (1, 'foo'), (2, 'bar');
2438+
CREATE INDEX concur_temp_ind_1 ON concur_temp_tab_1(c2);
2439+
REINDEX TABLE CONCURRENTLY concur_temp_tab_1;
2440+
REINDEX INDEX CONCURRENTLY concur_temp_ind_1;
2441+
-- Still fails in transaction blocks
2442+
BEGIN;
2443+
REINDEX INDEX CONCURRENTLY concur_temp_ind_1;
2444+
ERROR: REINDEX CONCURRENTLY cannot run inside a transaction block
2445+
COMMIT;
2446+
-- ON COMMIT DELETE ROWS
2447+
CREATE TEMP TABLE concur_temp_tab_2 (c1 int, c2 text)
2448+
ON COMMIT DELETE ROWS;
2449+
CREATE INDEX concur_temp_ind_2 ON concur_temp_tab_2(c2);
2450+
REINDEX TABLE CONCURRENTLY concur_temp_tab_2;
2451+
REINDEX INDEX CONCURRENTLY concur_temp_ind_2;
2452+
-- ON COMMIT DROP
2453+
BEGIN;
2454+
CREATE TEMP TABLE concur_temp_tab_3 (c1 int, c2 text)
2455+
ON COMMIT PRESERVE ROWS;
2456+
INSERT INTO concur_temp_tab_3 VALUES (1, 'foo'), (2, 'bar');
2457+
CREATE INDEX concur_temp_ind_3 ON concur_temp_tab_3(c2);
2458+
-- Fails when running in a transaction
2459+
REINDEX INDEX CONCURRENTLY concur_temp_ind_3;
2460+
ERROR: REINDEX CONCURRENTLY cannot run inside a transaction block
2461+
COMMIT;
2462+
-- REINDEX SCHEMA processes all temporary relations
2463+
CREATE TABLE reindex_temp_before AS
2464+
SELECT oid, relname, relfilenode, relkind, reltoastrelid
2465+
FROM pg_class
2466+
WHERE relname IN ('concur_temp_ind_1', 'concur_temp_ind_2');
2467+
SELECT pg_my_temp_schema()::regnamespace as temp_schema_name \gset
2468+
REINDEX SCHEMA CONCURRENTLY :temp_schema_name;
2469+
SELECT b.relname,
2470+
b.relkind,
2471+
CASE WHEN a.relfilenode = b.relfilenode THEN 'relfilenode is unchanged'
2472+
ELSE 'relfilenode has changed' END
2473+
FROM reindex_temp_before b JOIN pg_class a ON b.oid = a.oid
2474+
ORDER BY 1;
2475+
relname | relkind | case
2476+
-------------------+---------+-------------------------
2477+
concur_temp_ind_1 | i | relfilenode has changed
2478+
concur_temp_ind_2 | i | relfilenode has changed
2479+
(2 rows)
2480+
2481+
DROP TABLE concur_temp_tab_1, concur_temp_tab_2, reindex_temp_before;
24082482
--
24092483
-- REINDEX SCHEMA
24102484
--

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