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-rw-r--r--src/backend/commands/sequence.c69
1 files changed, 48 insertions, 21 deletions
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index 4a56926b530..0f7cf1dce8a 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -93,11 +93,12 @@ static HTAB *seqhashtab = NULL; /* hash table for SeqTable items */
static SeqTableData *last_used_seq = NULL;
static void fill_seq_with_data(Relation rel, HeapTuple tuple);
-static Relation open_share_lock(SeqTable seq);
+static Relation lock_and_open_sequence(SeqTable seq);
static void create_seq_hashtable(void);
static void init_sequence(Oid relid, SeqTable *p_elm, Relation *p_rel);
static Form_pg_sequence_data read_seq_tuple(Relation rel,
Buffer *buf, HeapTuple seqdatatuple);
+static LOCKMODE alter_sequence_get_lock_level(List *options);
static void init_params(ParseState *pstate, List *options, bool for_identity,
bool isInit,
Form_pg_sequence seqform,
@@ -427,7 +428,9 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
HeapTuple tuple;
/* Open and lock sequence. */
- relid = RangeVarGetRelid(stmt->sequence, AccessShareLock, stmt->missing_ok);
+ relid = RangeVarGetRelid(stmt->sequence,
+ alter_sequence_get_lock_level(stmt->options),
+ stmt->missing_ok);
if (relid == InvalidOid)
{
ereport(NOTICE,
@@ -443,12 +446,6 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
stmt->sequence->relname);
- /* lock page' buffer and read tuple into new sequence structure */
- seqdata = read_seq_tuple(seqrel, &buf, &seqdatatuple);
-
- /* Copy old sequence data into workspace */
- memcpy(&newseqdata, seqdata, sizeof(FormData_pg_sequence_data));
-
rel = heap_open(SequenceRelationId, RowExclusiveLock);
tuple = SearchSysCacheCopy1(SEQRELID,
ObjectIdGetDatum(relid));
@@ -458,6 +455,12 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
seqform = (Form_pg_sequence) GETSTRUCT(tuple);
+ /* lock page's buffer and read tuple into new sequence structure */
+ seqdata = read_seq_tuple(seqrel, &buf, &seqdatatuple);
+
+ /* Copy old sequence data into workspace */
+ memcpy(&newseqdata, seqdata, sizeof(FormData_pg_sequence_data));
+
/* Check and set new values */
init_params(pstate, stmt->options, stmt->for_identity, false, seqform, &changed_seqform, &newseqdata, &owned_by);
@@ -508,12 +511,12 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
ObjectAddressSet(address, RelationRelationId, relid);
- relation_close(seqrel, NoLock);
-
if (changed_seqform)
CatalogTupleUpdate(rel, &tuple->t_self, tuple);
heap_close(rel, RowExclusiveLock);
+ relation_close(seqrel, NoLock);
+
return address;
}
@@ -594,7 +597,7 @@ nextval_internal(Oid relid, bool check_permissions)
bool cycle;
bool logit = false;
- /* open and AccessShareLock sequence */
+ /* open and lock sequence */
init_sequence(relid, &elm, &seqrel);
if (check_permissions &&
@@ -829,7 +832,7 @@ currval_oid(PG_FUNCTION_ARGS)
SeqTable elm;
Relation seqrel;
- /* open and AccessShareLock sequence */
+ /* open and lock sequence */
init_sequence(relid, &elm, &seqrel);
if (pg_class_aclcheck(elm->relid, GetUserId(),
@@ -869,7 +872,7 @@ lastval(PG_FUNCTION_ARGS)
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("lastval is not yet defined in this session")));
- seqrel = open_share_lock(last_used_seq);
+ seqrel = lock_and_open_sequence(last_used_seq);
/* nextval() must have already been called for this sequence */
Assert(last_used_seq->last_valid);
@@ -913,7 +916,7 @@ do_setval(Oid relid, int64 next, bool iscalled)
int64 maxv,
minv;
- /* open and AccessShareLock sequence */
+ /* open and lock sequence */
init_sequence(relid, &elm, &seqrel);
if (pg_class_aclcheck(elm->relid, GetUserId(), ACL_UPDATE) != ACLCHECK_OK)
@@ -1042,15 +1045,15 @@ setval3_oid(PG_FUNCTION_ARGS)
/*
- * Open the sequence and acquire AccessShareLock if needed
+ * Open the sequence and acquire lock if needed
*
* If we haven't touched the sequence already in this transaction,
- * we need to acquire AccessShareLock. We arrange for the lock to
+ * we need to acquire a lock. We arrange for the lock to
* be owned by the top transaction, so that we don't need to do it
* more than once per xact.
*/
static Relation
-open_share_lock(SeqTable seq)
+lock_and_open_sequence(SeqTable seq)
{
LocalTransactionId thislxid = MyProc->lxid;
@@ -1063,7 +1066,7 @@ open_share_lock(SeqTable seq)
PG_TRY();
{
CurrentResourceOwner = TopTransactionResourceOwner;
- LockRelationOid(seq->relid, AccessShareLock);
+ LockRelationOid(seq->relid, RowExclusiveLock);
}
PG_CATCH();
{
@@ -1078,7 +1081,7 @@ open_share_lock(SeqTable seq)
seq->lxid = thislxid;
}
- /* We now know we have AccessShareLock, and can safely open the rel */
+ /* We now know we have the lock, and can safely open the rel */
return relation_open(seq->relid, NoLock);
}
@@ -1135,7 +1138,7 @@ init_sequence(Oid relid, SeqTable *p_elm, Relation *p_rel)
/*
* Open the sequence relation.
*/
- seqrel = open_share_lock(elm);
+ seqrel = lock_and_open_sequence(elm);
if (seqrel->rd_rel->relkind != RELKIND_SEQUENCE)
ereport(ERROR,
@@ -1217,6 +1220,30 @@ read_seq_tuple(Relation rel, Buffer *buf, HeapTuple seqdatatuple)
}
/*
+ * Check the sequence options list and return the appropriate lock level for
+ * ALTER SEQUENCE.
+ *
+ * Most sequence option changes require a self-exclusive lock and should block
+ * concurrent nextval() et al. But RESTART does not, because it's not
+ * transactional. Also take a lower lock if no option at all is present.
+ */
+static LOCKMODE
+alter_sequence_get_lock_level(List *options)
+{
+ ListCell *option;
+
+ foreach(option, options)
+ {
+ DefElem *defel = (DefElem *) lfirst(option);
+
+ if (strcmp(defel->defname, "restart") != 0)
+ return ShareRowExclusiveLock;
+ }
+
+ return RowExclusiveLock;
+}
+
+/*
* init_params: process the options list of CREATE or ALTER SEQUENCE, and
* store the values into appropriate fields of seqform, for changes that go
* into the pg_sequence catalog, and seqdataform for changes to the sequence
@@ -1850,7 +1877,7 @@ pg_sequence_last_value(PG_FUNCTION_ARGS)
bool is_called;
int64 result;
- /* open and AccessShareLock sequence */
+ /* open and lock sequence */
init_sequence(relid, &elm, &seqrel);
if (pg_class_aclcheck(relid, GetUserId(), ACL_SELECT | ACL_USAGE) != ACLCHECK_OK)
generated by cgit v1.2.3 (git 2.25.1) at 2025-05-23 07:22:43 +0000