Implement IF NOT EXISTS for CREATE SEQUENCE.

Fabrízio de Royes Mello

1 files changed, 19 insertions, 1 deletions

diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index e6084203a88..3b89dd009bc 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -122,6 +122,24 @@ DefineSequence(CreateSeqStmt *seq)
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("unlogged sequences are not supported")));
 
+	/*
+	 * If if_not_exists was given and a relation with the same name already
+	 * exists, bail out. (Note: we needn't check this when not if_not_exists,
+	 * because DefineRelation will complain anyway.)
+	 */
+	if (seq->if_not_exists)
+	{
+		RangeVarGetAndCheckCreationNamespace(seq->sequence, NoLock, &seqoid);
+		if (OidIsValid(seqoid))
+		{
+			ereport(NOTICE,
+					(errcode(ERRCODE_DUPLICATE_TABLE),
+					 errmsg("relation \"%s\" already exists, skipping",
+							seq->sequence->relname)));
+			return InvalidOid;
+		}
+	}
+
 	/* Check and set all option values */
 	init_params(seq->options, true, &new, &owned_by);
 
@@ -210,7 +228,7 @@ DefineSequence(CreateSeqStmt *seq)
 	stmt->options = NIL;
 	stmt->oncommit = ONCOMMIT_NOOP;
 	stmt->tablespacename = NULL;
-	stmt->if_not_exists = false;
+	stmt->if_not_exists = seq->if_not_exists;
 
 	seqoid = DefineRelation(stmt, RELKIND_SEQUENCE, seq->ownerId);
 	Assert(seqoid != InvalidOid);