From 3f11139b5cedc59f320e75a73ea921b20b9562bb Mon Sep 17 00:00:00 2001
From: ahmet gedemenli <afgedemenli@gmail.com>
Date: Thu, 20 Jul 2023 16:39:56 +0300
Subject: [PATCH] Do not move a shard to a node that it already exists on

---
 src/backend/distributed/operations/shard_rebalancer.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/backend/distributed/operations/shard_rebalancer.c b/src/backend/distributed/operations/shard_rebalancer.c
index 61a4ee9b0..d26c7baf2 100644
--- a/src/backend/distributed/operations/shard_rebalancer.c
+++ b/src/backend/distributed/operations/shard_rebalancer.c
@@ -2796,7 +2796,15 @@ FindAllowedTargetFillState(RebalanceState *state, uint64 shardId)
 				targetFillState->node,
 				state->functions->context))
 		{
-			return targetFillState;
+			bool targetHasShard = PlacementsHashFind(state->placementsHash,
+													 shardId,
+													 targetFillState->node);
+
+			/* skip if the shard is already placed on the target node */
+			if (!targetHasShard)
+			{
+				return targetFillState;
+			}
 		}
 	}
 	return NULL;