1 files changed, 32 insertions, 91 deletions

diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index 568b3022f2d..4a56f03e8b6 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -98,11 +98,9 @@ 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,
-			bool *changed_seqform,
 			Form_pg_sequence_data seqdataform, List **owned_by);
 static void do_setval(Oid relid, int64 next, bool iscalled);
 static void process_owned_by(Relation seqrel, List *owned_by, bool for_identity);
@@ -117,7 +115,6 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
 {
 	FormData_pg_sequence seqform;
 	FormData_pg_sequence_data seqdataform;
-	bool		changed_seqform = false;		/* not used here */
 	List	   *owned_by;
 	CreateStmt *stmt = makeNode(CreateStmt);
 	Oid			seqoid;
@@ -156,7 +153,7 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
 	}
 
 	/* Check and set all option values */
-	init_params(pstate, seq->options, seq->for_identity, true, &seqform, &changed_seqform, &seqdataform, &owned_by);
+	init_params(pstate, seq->options, seq->for_identity, true, &seqform, &seqdataform, &owned_by);
 
 	/*
 	 * Create relation (and fill value[] and null[] for the tuple)
@@ -417,19 +414,18 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
 	SeqTable	elm;
 	Relation	seqrel;
 	Buffer		buf;
-	HeapTupleData seqdatatuple;
+	HeapTupleData datatuple;
 	Form_pg_sequence seqform;
-	Form_pg_sequence_data seqdata;
-	FormData_pg_sequence_data newseqdata;
-	bool		changed_seqform = false;
+	Form_pg_sequence_data newdataform;
 	List	   *owned_by;
 	ObjectAddress address;
 	Relation	rel;
-	HeapTuple	tuple;
+	HeapTuple	seqtuple;
+	HeapTuple	newdatatuple;
 
 	/* Open and lock sequence. */
 	relid = RangeVarGetRelid(stmt->sequence,
-							 alter_sequence_get_lock_level(stmt->options),
+							 ShareRowExclusiveLock,
 							 stmt->missing_ok);
 	if (relid == InvalidOid)
 	{
@@ -447,22 +443,26 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
 					   stmt->sequence->relname);
 
 	rel = heap_open(SequenceRelationId, RowExclusiveLock);
-	tuple = SearchSysCacheCopy1(SEQRELID,
-								ObjectIdGetDatum(relid));
-	if (!HeapTupleIsValid(tuple))
+	seqtuple = SearchSysCacheCopy1(SEQRELID,
+								   ObjectIdGetDatum(relid));
+	if (!HeapTupleIsValid(seqtuple))
 		elog(ERROR, "cache lookup failed for sequence %u",
 			 relid);
 
-	seqform = (Form_pg_sequence) GETSTRUCT(tuple);
+	seqform = (Form_pg_sequence) GETSTRUCT(seqtuple);
 
 	/* lock page's buffer and read tuple into new sequence structure */
-	seqdata = read_seq_tuple(seqrel, &buf, &seqdatatuple);
+	(void) read_seq_tuple(seqrel, &buf, &datatuple);
 
-	/* Copy old sequence data into workspace */
-	memcpy(&newseqdata, seqdata, sizeof(FormData_pg_sequence_data));
+	/* copy the existing sequence data tuple, so it can be modified localy */
+	newdatatuple = heap_copytuple(&datatuple);
+	newdataform = (Form_pg_sequence_data) GETSTRUCT(newdatatuple);
+
+	UnlockReleaseBuffer(buf);
 
 	/* Check and set new values */
-	init_params(pstate, stmt->options, stmt->for_identity, false, seqform, &changed_seqform, &newseqdata, &owned_by);
+	init_params(pstate, stmt->options, stmt->for_identity, false, seqform,
+				newdataform, &owned_by);
 
 	/* Clear local cache so that we don't think we have cached numbers */
 	/* Note that we do not change the currval() state */
@@ -472,36 +472,19 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
 	if (RelationNeedsWAL(seqrel))
 		GetTopTransactionId();
 
-	/* Now okay to update the on-disk tuple */
-	START_CRIT_SECTION();
-
-	memcpy(seqdata, &newseqdata, sizeof(FormData_pg_sequence_data));
-
-	MarkBufferDirty(buf);
-
-	/* XLOG stuff */
-	if (RelationNeedsWAL(seqrel))
-	{
-		xl_seq_rec	xlrec;
-		XLogRecPtr	recptr;
-		Page		page = BufferGetPage(buf);
-
-		XLogBeginInsert();
-		XLogRegisterBuffer(0, buf, REGBUF_WILL_INIT);
-
-		xlrec.node = seqrel->rd_node;
-		XLogRegisterData((char *) &xlrec, sizeof(xl_seq_rec));
-
-		XLogRegisterData((char *) seqdatatuple.t_data, seqdatatuple.t_len);
-
-		recptr = XLogInsert(RM_SEQ_ID, XLOG_SEQ_LOG);
-
-		PageSetLSN(page, recptr);
-	}
-
-	END_CRIT_SECTION();
+	/*
+	 * Create a new storage file for the sequence, making the state changes
+	 * transactional.  We want to keep the sequence's relfrozenxid at 0, since
+	 * it won't contain any unfrozen XIDs.  Same with relminmxid, since a
+	 * sequence will never contain multixacts.
+	 */
+	RelationSetNewRelfilenode(seqrel, seqrel->rd_rel->relpersistence,
+							  InvalidTransactionId, InvalidMultiXactId);
 
-	UnlockReleaseBuffer(buf);
+	/*
+	 * Insert the modified tuple into the new storage file.
+	 */
+	fill_seq_with_data(seqrel, newdatatuple);
 
 	/* process OWNED BY if given */
 	if (owned_by)
@@ -511,10 +494,9 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
 
 	ObjectAddressSet(address, RelationRelationId, relid);
 
-	if (changed_seqform)
-		CatalogTupleUpdate(rel, &tuple->t_self, tuple);
-	heap_close(rel, RowExclusiveLock);
+	CatalogTupleUpdate(rel, &seqtuple->t_self, seqtuple);
 
+	heap_close(rel, RowExclusiveLock);
 	relation_close(seqrel, NoLock);
 
 	return address;
@@ -1220,30 +1202,6 @@ 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
@@ -1258,7 +1216,6 @@ static void
 init_params(ParseState *pstate, List *options, bool for_identity,
 			bool isInit,
 			Form_pg_sequence seqform,
-			bool *changed_seqform,
 			Form_pg_sequence_data seqdataform,
 			List **owned_by)
 {
@@ -1378,8 +1335,6 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 				 defel->defname);
 	}
 
-	*changed_seqform = false;
-
 	/*
 	 * We must reset log_cnt when isInit or when changing any parameters that
 	 * would affect future nextval allocations.
@@ -1420,19 +1375,16 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 		}
 
 		seqform->seqtypid = newtypid;
-		*changed_seqform = true;
 	}
 	else if (isInit)
 	{
 		seqform->seqtypid = INT8OID;
-		*changed_seqform = true;
 	}
 
 	/* INCREMENT BY */
 	if (increment_by != NULL)
 	{
 		seqform->seqincrement = defGetInt64(increment_by);
-		*changed_seqform = true;
 		if (seqform->seqincrement == 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
@@ -1442,28 +1394,24 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 	else if (isInit)
 	{
 		seqform->seqincrement = 1;
-		*changed_seqform = true;
 	}
 
 	/* CYCLE */
 	if (is_cycled != NULL)
 	{
 		seqform->seqcycle = intVal(is_cycled->arg);
-		*changed_seqform = true;
 		Assert(BoolIsValid(seqform->seqcycle));
 		seqdataform->log_cnt = 0;
 	}
 	else if (isInit)
 	{
 		seqform->seqcycle = false;
-		*changed_seqform = true;
 	}
 
 	/* MAXVALUE (null arg means NO MAXVALUE) */
 	if (max_value != NULL && max_value->arg)
 	{
 		seqform->seqmax = defGetInt64(max_value);
-		*changed_seqform = true;
 		seqdataform->log_cnt = 0;
 	}
 	else if (isInit || max_value != NULL || reset_max_value)
@@ -1480,7 +1428,6 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 		}
 		else
 			seqform->seqmax = -1;		/* descending seq */
-		*changed_seqform = true;
 		seqdataform->log_cnt = 0;
 	}
 
@@ -1502,7 +1449,6 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 	if (min_value != NULL && min_value->arg)
 	{
 		seqform->seqmin = defGetInt64(min_value);
-		*changed_seqform = true;
 		seqdataform->log_cnt = 0;
 	}
 	else if (isInit || min_value != NULL || reset_min_value)
@@ -1519,7 +1465,6 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 		}
 		else
 			seqform->seqmin = 1;	/* ascending seq */
-		*changed_seqform = true;
 		seqdataform->log_cnt = 0;
 	}
 
@@ -1555,7 +1500,6 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 	if (start_value != NULL)
 	{
 		seqform->seqstart = defGetInt64(start_value);
-		*changed_seqform = true;
 	}
 	else if (isInit)
 	{
@@ -1563,7 +1507,6 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 			seqform->seqstart = seqform->seqmin;		/* ascending seq */
 		else
 			seqform->seqstart = seqform->seqmax;		/* descending seq */
-		*changed_seqform = true;
 	}
 
 	/* crosscheck START */
@@ -1638,7 +1581,6 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 	if (cache_value != NULL)
 	{
 		seqform->seqcache = defGetInt64(cache_value);
-		*changed_seqform = true;
 		if (seqform->seqcache <= 0)
 		{
 			char		buf[100];
@@ -1654,7 +1596,6 @@ init_params(ParseState *pstate, List *options, bool for_identity,
 	else if (isInit)
 	{
 		seqform->seqcache = 1;
-		*changed_seqform = true;
 	}
 }