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Introduce sequence_*() access functions
Similarly to tables and indexes, these functions are able to open relations with a sequence relkind, which is useful to make a distinction with the other relation kinds. Previously, commands/sequence.c used a mix of table_{close,open}() and relation_{close,open}() routines when manipulating sequence relations, so this clarifies the code. A direct effect of this change is to align the error messages produced when attempting DDLs for sequences on relations with an unexpected relkind, like a table or an index with ALTER SEQUENCE, providing an extra error detail about the relkind of the relation used in the DDL query. Author: Michael Paquier Reviewed-by: Tomas Vondra Discussion: https://postgr.es/m/ZWlohtKAs0uVVpZ3@paquier.xyz
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8 files changed

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‎src/backend/access/Makefile

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -9,6 +9,6 @@ top_builddir = ../../..
99
include $(top_builddir)/src/Makefile.global
1010

1111
SUBDIRS = brin common gin gist hash heap index nbtree rmgrdesc spgist \
12-
table tablesample transam
12+
sequence table tablesample transam
1313

1414
include $(top_srcdir)/src/backend/common.mk

‎src/backend/access/meson.build

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -9,6 +9,7 @@ subdir('heap')
99
subdir('index')
1010
subdir('nbtree')
1111
subdir('rmgrdesc')
12+
subdir('sequence')
1213
subdir('spgist')
1314
subdir('table')
1415
subdir('tablesample')

‎src/backend/access/sequence/Makefile

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,17 @@
1+
#-------------------------------------------------------------------------
2+
#
3+
# Makefile
4+
# Makefile for access/sequence
5+
#
6+
# IDENTIFICATION
7+
# src/backend/access/sequence/Makefile
8+
#
9+
#-------------------------------------------------------------------------
10+
11+
subdir = src/backend/access/sequence
12+
top_builddir = ../../../..
13+
include $(top_builddir)/src/Makefile.global
14+
15+
OBJS = sequence.o
16+
17+
include $(top_srcdir)/src/backend/common.mk

‎src/backend/access/sequence/meson.build

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@@ -0,0 +1,5 @@
1+
# Copyright (c) 2022-2024, PostgreSQL Global Development Group
2+
3+
backend_sources += files(
4+
'sequence.c',
5+
)

‎src/backend/access/sequence/sequence.c

Lines changed: 78 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,78 @@
1+
/*-------------------------------------------------------------------------
2+
*
3+
* sequence.c
4+
* Generic routines for sequence-related code.
5+
*
6+
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
7+
* Portions Copyright (c) 1994, Regents of the University of California
8+
*
9+
*
10+
* IDENTIFICATION
11+
* src/backend/access/sequence/sequence.c
12+
*
13+
*
14+
* NOTES
15+
* This file contains sequence_ routines that implement access to sequences
16+
* (in contrast to other relation types like indexes).
17+
*
18+
*-------------------------------------------------------------------------
19+
*/
20+
21+
#include "postgres.h"
22+
23+
#include "access/relation.h"
24+
#include "access/sequence.h"
25+
#include "storage/lmgr.h"
26+
27+
static inline void validate_relation_kind(Relation r);
28+
29+
/* ----------------
30+
* sequence_open - open a sequence relation by relation OID
31+
*
32+
* This is essentially relation_open plus check that the relation
33+
* is a sequence.
34+
* ----------------
35+
*/
36+
Relation
37+
sequence_open(Oid relationId, LOCKMODE lockmode)
38+
{
39+
Relation r;
40+
41+
r = relation_open(relationId, lockmode);
42+
43+
validate_relation_kind(r);
44+
45+
return r;
46+
}
47+
48+
/* ----------------
49+
* sequence_close - close a sequence
50+
*
51+
* If lockmode is not "NoLock", we then release the specified lock.
52+
*
53+
* Note that it is often sensible to hold a lock beyond relation_close;
54+
* in that case, the lock is released automatically at xact end.
55+
* ----------------
56+
*/
57+
void
58+
sequence_close(Relation relation, LOCKMODE lockmode)
59+
{
60+
relation_close(relation, lockmode);
61+
}
62+
63+
/* ----------------
64+
* validate_relation_kind - check the relation's kind
65+
*
66+
* Make sure relkind is from an index
67+
* ----------------
68+
*/
69+
static inline void
70+
validate_relation_kind(Relation r)
71+
{
72+
if (r->rd_rel->relkind != RELKIND_SEQUENCE)
73+
ereport(ERROR,
74+
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
75+
errmsg("cannot open relation \"%s\"",
76+
RelationGetRelationName(r)),
77+
errdetail_relkind_not_supported(r->rd_rel->relkind)));
78+
}

‎src/backend/commands/sequence.c

Lines changed: 13 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,7 @@
1818
#include "access/htup_details.h"
1919
#include "access/multixact.h"
2020
#include "access/relation.h"
21+
#include "access/sequence.h"
2122
#include "access/table.h"
2223
#include "access/transam.h"
2324
#include "access/xact.h"
@@ -208,7 +209,7 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
208209
seqoid = address.objectId;
209210
Assert(seqoid != InvalidOid);
210211

211-
rel = table_open(seqoid, AccessExclusiveLock);
212+
rel = sequence_open(seqoid, AccessExclusiveLock);
212213
tupDesc = RelationGetDescr(rel);
213214

214215
/* now initialize the sequence's data */
@@ -219,7 +220,7 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
219220
if (owned_by)
220221
process_owned_by(rel, owned_by, seq->for_identity);
221222

222-
table_close(rel, NoLock);
223+
sequence_close(rel, NoLock);
223224

224225
/* fill in pg_sequence */
225226
rel = table_open(SequenceRelationId, RowExclusiveLock);
@@ -324,7 +325,7 @@ ResetSequence(Oid seq_relid)
324325
/* Note that we do not change the currval() state */
325326
elm->cached = elm->last;
326327

327-
relation_close(seq_rel, NoLock);
328+
sequence_close(seq_rel, NoLock);
328329
}
329330

330331
/*
@@ -531,7 +532,7 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
531532
ObjectAddressSet(address, RelationRelationId, relid);
532533

533534
table_close(rel, RowExclusiveLock);
534-
relation_close(seqrel, NoLock);
535+
sequence_close(seqrel, NoLock);
535536

536537
return address;
537538
}
@@ -555,7 +556,7 @@ SequenceChangePersistence(Oid relid, char newrelpersistence)
555556
fill_seq_with_data(seqrel, &seqdatatuple);
556557
UnlockReleaseBuffer(buf);
557558

558-
relation_close(seqrel, NoLock);
559+
sequence_close(seqrel, NoLock);
559560
}
560561

561562
void
@@ -662,7 +663,7 @@ nextval_internal(Oid relid, bool check_permissions)
662663
Assert(elm->last_valid);
663664
Assert(elm->increment != 0);
664665
elm->last += elm->increment;
665-
relation_close(seqrel, NoLock);
666+
sequence_close(seqrel, NoLock);
666667
last_used_seq = elm;
667668
return elm->last;
668669
}
@@ -849,7 +850,7 @@ nextval_internal(Oid relid, bool check_permissions)
849850

850851
UnlockReleaseBuffer(buf);
851852

852-
relation_close(seqrel, NoLock);
853+
sequence_close(seqrel, NoLock);
853854

854855
return result;
855856
}
@@ -880,7 +881,7 @@ currval_oid(PG_FUNCTION_ARGS)
880881

881882
result = elm->last;
882883

883-
relation_close(seqrel, NoLock);
884+
sequence_close(seqrel, NoLock);
884885

885886
PG_RETURN_INT64(result);
886887
}
@@ -915,7 +916,7 @@ lastval(PG_FUNCTION_ARGS)
915916
RelationGetRelationName(seqrel))));
916917

917918
result = last_used_seq->last;
918-
relation_close(seqrel, NoLock);
919+
sequence_close(seqrel, NoLock);
919920

920921
PG_RETURN_INT64(result);
921922
}
@@ -1030,7 +1031,7 @@ do_setval(Oid relid, int64 next, bool iscalled)
10301031

10311032
UnlockReleaseBuffer(buf);
10321033

1033-
relation_close(seqrel, NoLock);
1034+
sequence_close(seqrel, NoLock);
10341035
}
10351036

10361037
/*
@@ -1095,7 +1096,7 @@ lock_and_open_sequence(SeqTable seq)
10951096
}
10961097

10971098
/* We now know we have the lock, and can safely open the rel */
1098-
return relation_open(seq->relid, NoLock);
1099+
return sequence_open(seq->relid, NoLock);
10991100
}
11001101

11011102
/*
@@ -1152,12 +1153,6 @@ init_sequence(Oid relid, SeqTable *p_elm, Relation *p_rel)
11521153
*/
11531154
seqrel = lock_and_open_sequence(elm);
11541155

1155-
if (seqrel->rd_rel->relkind != RELKIND_SEQUENCE)
1156-
ereport(ERROR,
1157-
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
1158-
errmsg("\"%s\" is not a sequence",
1159-
RelationGetRelationName(seqrel))));
1160-
11611156
/*
11621157
* If the sequence has been transactionally replaced since we last saw it,
11631158
* discard any cached-but-unissued values. We do not touch the currval()
@@ -1803,7 +1798,7 @@ pg_sequence_last_value(PG_FUNCTION_ARGS)
18031798
result = seq->last_value;
18041799

18051800
UnlockReleaseBuffer(buf);
1806-
relation_close(seqrel, NoLock);
1801+
sequence_close(seqrel, NoLock);
18071802

18081803
if (is_called)
18091804
PG_RETURN_INT64(result);

‎src/include/access/sequence.h

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
1+
/*-------------------------------------------------------------------------
2+
*
3+
* sequence.h
4+
* Generic routines for sequence-related code.
5+
*
6+
*
7+
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
8+
* Portions Copyright (c) 1994, Regents of the University of California
9+
*
10+
* src/include/access/sequence.h
11+
*
12+
*-------------------------------------------------------------------------
13+
*/
14+
#ifndef ACCESS_SEQUENCE_H
15+
#define ACCESS_SEQUENCE_H
16+
17+
#include "storage/lockdefs.h"
18+
#include "utils/relcache.h"
19+
20+
extern Relation sequence_open(Oid relationId, LOCKMODE lockmode);
21+
extern void sequence_close(Relation relation, LOCKMODE lockmode);
22+
23+
#endif /* ACCESS_SEQUENCE_H */

‎src/test/regress/expected/sequence.out

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -313,7 +313,8 @@ ALTER SEQUENCE IF EXISTS sequence_test2 RESTART WITH 24
313313
INCREMENT BY 4 MAXVALUE 36 MINVALUE 5 CYCLE;
314314
NOTICE: relation "sequence_test2" does not exist, skipping
315315
ALTER SEQUENCE serialTest1 CYCLE; -- error, not a sequence
316-
ERROR: "serialtest1" is not a sequence
316+
ERROR: cannot open relation "serialtest1"
317+
DETAIL: This operation is not supported for tables.
317318
CREATE SEQUENCE sequence_test2 START WITH 32;
318319
CREATE SEQUENCE sequence_test4 INCREMENT BY -1;
319320
SELECT nextval('sequence_test2');

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