On Thu, Jan 08, 2026 at 01:19:39PM -0500, Tom Lane wrote: > One nitpicky point is that try_sequence_open() will still error out > if it is given an OID that is a non-sequence relation. I think it'd > be more desirable for it to close the relation again and return NULL. > That's probably insignificant for pg_dump's usage, because we could > only hit the case with very improbable OID wraparound timing. But > I think our experience with catalog-inspection functions similar to > pg_get_sequence_data is that it's usually better to return NULL than > throw an error.
Hm. That makes sense, but both try_table_open and try_index_open error for wrong relkinds. I could change all of the try_*_open functions to return NULL in that case, or I could just open-code the relkind check in pg_get_sequence_data after try_relation_open (and have it return NULL for non-sequences). I'm leaning towards the latter, if for no other reason than it might be slightly nicer for back-patching (e.g., smaller, no new extern functions). -- nathan
>From 68a9b7fb9714805819b040f19851601f1426c990 Mon Sep 17 00:00:00 2001 From: Nathan Bossart <[email protected]> Date: Thu, 8 Jan 2026 11:29:59 -0600 Subject: [PATCH v2 1/1] pg_dump: fix use of pg_get_sequence_data --- src/backend/commands/sequence.c | 14 ++++++++------ src/bin/pg_dump/pg_dump.c | 10 ++++++++++ 2 files changed, 18 insertions(+), 6 deletions(-) diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c index 904eeada5ab..e1b808bbb60 100644 --- a/src/backend/commands/sequence.c +++ b/src/backend/commands/sequence.c @@ -1794,7 +1794,6 @@ pg_get_sequence_data(PG_FUNCTION_ARGS) { #define PG_GET_SEQUENCE_DATA_COLS 3 Oid relid = PG_GETARG_OID(0); - SeqTable elm; Relation seqrel; Datum values[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); 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 - * sessions' temporary sequences, and unlogged sequences on standbys. + * Return all NULLs for missing sequences, sequences for which we lack + * 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) && (RelationIsPermanent(seqrel) || !RecoveryInProgress())) { @@ -1838,7 +1839,8 @@ pg_get_sequence_data(PG_FUNCTION_ARGS) else memset(isnull, true, sizeof(isnull)); - sequence_close(seqrel, NoLock); + if (seqrel) + relation_close(seqrel, AccessShareLock); resultHeapTuple = heap_form_tuple(resultTupleDesc, values, isnull); result = HeapTupleGetDatum(resultHeapTuple); diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c index 7df56d8b1b0..573fb0c06a1 100644 --- a/src/bin/pg_dump/pg_dump.c +++ b/src/bin/pg_dump/pg_dump.c @@ -137,6 +137,7 @@ typedef struct int64 cache; /* cache size */ int64 last_value; /* last value of sequence */ bool is_called; /* whether nextval advances before returning */ + bool null_seqtuple; /* did pg_get_sequence_data return nulls? */ } SequenceItem; typedef enum OidOptions @@ -18959,6 +18960,7 @@ collectSequences(Archive *fout) sequences[i].cycled = (strcmp(PQgetvalue(res, i, 7), "t") == 0); sequences[i].last_value = strtoi64(PQgetvalue(res, i, 8), NULL, 10); 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); @@ -19230,6 +19232,10 @@ dumpSequenceData(Archive *fout, const TableDataInfo *tdinfo) bool called; 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 * array before any calls to dumpSequenceData(). See collectSequences() @@ -19271,6 +19277,10 @@ dumpSequenceData(Archive *fout, const TableDataInfo *tdinfo) entry = bsearch(&key, sequences, nsequences, sizeof(SequenceItem), SequenceItemCmp); + if (entry->null_seqtuple) + pg_fatal("failed to get data for sequence \"%s\"; user may lack privileges or sequence may have been dropped", + tbinfo->dobj.name); + last = entry->last_value; called = entry->is_called; } -- 2.39.5 (Apple Git-154)
