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pg_dump: Fix gathering of sequence information.

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Since commit bd15b7db48, pg_dump uses pg_get_sequence_data() (née
pg_sequence_read_tuple()) to gather all sequence data in a single
query as opposed to a query per sequence.  Two related bugs have
been identified:

* If the user lacks appropriate privileges on the sequence, pg_dump
generates a setval() command with garbage values instead of
failing as expected.

* pg_dump can fail due to a concurrently dropped sequence, even if
the dropped sequence's data isn't part of the dump.

This commit fixes the above issues by 1) teaching
pg_get_sequence_data() to return nulls instead of erroring for a
missing sequence and 2) teaching pg_dump to fail if it tries to
dump the data of a sequence for which pg_get_sequence_data()
returned nulls.  Note that pg_dump may still fail due to a
concurrently dropped sequence, but it should now only do so when
the sequence data is part of the dump.  This matches the behavior
before commit bd15b7db48.

Bug: #19365
Reported-by: Paveł Tyślacki <pavel.tyslacki@gmail.com>
Suggested-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/19365-6245240d8b926327%40postgresql.org
Discussion: https://postgr.es/m/2885944.1767029161%40sss.pgh.pa.us
Backpatch-through: 18
This commit is contained in:
Nathan Bossart 2026-01-09 10:12:54 -06:00
parent 24cb3a08a4
commit 7a485bd641
2 changed files with 20 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

14
src/backend/commands/sequence.c
View file

@ -1794,7 +1794,6 @@ pg_get_sequence_data(PG_FUNCTION_ARGS)
{ {
#define PG_GET_SEQUENCE_DATA_COLS 3 #define PG_GET_SEQUENCE_DATA_COLS 3
Oid relid = PG_GETARG_OID(0); Oid relid = PG_GETARG_OID(0);
SeqTable elm;
Relation seqrel; Relation seqrel;
Datum values[PG_GET_SEQUENCE_DATA_COLS] = {0}; Datum values[PG_GET_SEQUENCE_DATA_COLS] = {0};
bool isnull[PG_GET_SEQUENCE_DATA_COLS] = {0}; bool isnull[PG_GET_SEQUENCE_DATA_COLS] = {0};
@ -1811,13 +1810,15 @@ pg_get_sequence_data(PG_FUNCTION_ARGS)
LSNOID, -1, 0); LSNOID, -1, 0);
resultTupleDesc = BlessTupleDesc(resultTupleDesc); resultTupleDesc = BlessTupleDesc(resultTupleDesc);
init_sequence(relid, &elm, &seqrel); seqrel = try_relation_open(relid, AccessShareLock);
/* /*
* Return all NULLs for sequences for which we lack privileges, other * Return all NULLs for missing sequences, sequences for which we lack
* sessions' temporary sequences, and unlogged sequences on standbys. * privileges, other sessions' temporary sequences, and unlogged sequences
* on standbys.
*/ */
if (pg_class_aclcheck(relid, GetUserId(), ACL_SELECT) == ACLCHECK_OK && if (seqrel && seqrel->rd_rel->relkind == RELKIND_SEQUENCE &&
pg_class_aclcheck(relid, GetUserId(), ACL_SELECT) == ACLCHECK_OK &&
!RELATION_IS_OTHER_TEMP(seqrel) && !RELATION_IS_OTHER_TEMP(seqrel) &&
(RelationIsPermanent(seqrel) || !RecoveryInProgress())) (RelationIsPermanent(seqrel) || !RecoveryInProgress()))
{ {
@ -1838,7 +1839,8 @@ pg_get_sequence_data(PG_FUNCTION_ARGS)
else else
memset(isnull, true, sizeof(isnull)); memset(isnull, true, sizeof(isnull));
sequence_close(seqrel, NoLock); if (seqrel)
relation_close(seqrel, AccessShareLock);
resultHeapTuple = heap_form_tuple(resultTupleDesc, values, isnull); resultHeapTuple = heap_form_tuple(resultTupleDesc, values, isnull);
result = HeapTupleGetDatum(resultHeapTuple); result = HeapTupleGetDatum(resultHeapTuple);

12
src/bin/pg_dump/pg_dump.c
View file

@ -137,6 +137,7 @@ typedef struct
int64 cache; /* cache size */ int64 cache; /* cache size */
int64 last_value; /* last value of sequence */ int64 last_value; /* last value of sequence */
bool is_called; /* whether nextval advances before returning */ bool is_called; /* whether nextval advances before returning */
bool null_seqtuple; /* did pg_get_sequence_data return nulls? */
} SequenceItem; } SequenceItem;
typedef enum OidOptions typedef enum OidOptions
@ -18959,6 +18960,7 @@ collectSequences(Archive *fout)
sequences[i].cycled = (strcmp(PQgetvalue(res, i, 7), "t") == 0); sequences[i].cycled = (strcmp(PQgetvalue(res, i, 7), "t") == 0);
sequences[i].last_value = strtoi64(PQgetvalue(res, i, 8), NULL, 10); sequences[i].last_value = strtoi64(PQgetvalue(res, i, 8), NULL, 10);
sequences[i].is_called = (strcmp(PQgetvalue(res, i, 9), "t") == 0); sequences[i].is_called = (strcmp(PQgetvalue(res, i, 9), "t") == 0);
sequences[i].null_seqtuple = (PQgetisnull(res, i, 8) || PQgetisnull(res, i, 9));
} }
PQclear(res); PQclear(res);
@ -19230,6 +19232,10 @@ dumpSequenceData(Archive *fout, const TableDataInfo *tdinfo)
bool called; bool called;
PQExpBuffer query = createPQExpBuffer(); PQExpBuffer query = createPQExpBuffer();
/* needn't bother if not dumping sequence data */
if (!fout->dopt->dumpData && !fout->dopt->sequence_data)
return;
/* /*
* For versions >= 18, the sequence information is gathered in the sorted * For versions >= 18, the sequence information is gathered in the sorted
* array before any calls to dumpSequenceData(). See collectSequences() * array before any calls to dumpSequenceData(). See collectSequences()
@ -19271,6 +19277,12 @@ dumpSequenceData(Archive *fout, const TableDataInfo *tdinfo)
entry = bsearch(&key, sequences, nsequences, entry = bsearch(&key, sequences, nsequences,
sizeof(SequenceItem), SequenceItemCmp); sizeof(SequenceItem), SequenceItemCmp);
if (entry->null_seqtuple)
pg_fatal("failed to get data for sequence \"%s\"; user may lack "
"SELECT privilege on the sequence or the sequence may "
"have been concurrently dropped",
tbinfo->dobj.name);
last = entry->last_value; last = entry->last_value;
called = entry->is_called; called = entry->is_called;
} }