From 3e5afb2d6e96aeaf2b03335a4046546aa4b950cb Mon Sep 17 00:00:00 2001
From: Mehmet YILMAZ <mehmet.yilmaz@microsoft.com>
Date: Wed, 4 Sep 2024 14:50:03 +0000
Subject: [PATCH] Add the locking mechanism before the check for whether the
 coordinator already exists

---
 citus-tools                                      | 1 +
 src/backend/distributed/metadata/node_metadata.c | 3 +++
 2 files changed, 4 insertions(+)
 create mode 160000 citus-tools

diff --git a/citus-tools b/citus-tools
new file mode 160000
index 00000000000..3376bd6845f
--- /dev/null
+++ b/citus-tools
@@ -0,0 +1 @@
+Subproject commit 3376bd6845f0614908ed304f5033bd644c82d3bf
diff --git a/src/backend/distributed/metadata/node_metadata.c b/src/backend/distributed/metadata/node_metadata.c
index d93b133eaed..d9220594317 100644
--- a/src/backend/distributed/metadata/node_metadata.c
+++ b/src/backend/distributed/metadata/node_metadata.c
@@ -217,6 +217,9 @@ citus_set_coordinator_host(PG_FUNCTION_ARGS)
 		EnsureTransactionalMetadataSyncMode();
 	}
 
+	/* prevent concurrent modification */
+	LockRelationOid(DistNodeRelationId(), RowExclusiveLock);
+
 	bool isCoordinatorInMetadata = false;
 	WorkerNode *coordinatorNode = PrimaryNodeForGroup(COORDINATOR_GROUP_ID,
 													  &isCoordinatorInMetadata);