Print notification for each colocated shard.

src/backend/distributed/operations/shard_rebalancer.c

@@ -861,15 +861,28 @@ ExecutePlacementUpdates(List *placementUpdateList, Oid shardReplicationModeOid,
 	foreach(placementUpdateCell, placementUpdateList)
 	{
 		PlacementUpdateEvent *placementUpdate = lfirst(placementUpdateCell);
-		ereport(NOTICE, (errmsg(
-							 "%s shard %lu from %s:%u to %s:%u ...",
-							 noticeOperation,
-							 placementUpdate->shardId,
-							 placementUpdate->sourceNode->workerName,
-							 placementUpdate->sourceNode->workerPort,
-							 placementUpdate->targetNode->workerName,
-							 placementUpdate->targetNode->workerPort
-							 )));
+		List *colocatedUpdateList = GetColocatedRebalanceSteps(list_make1(
+																   placementUpdate));
+		ListCell *colocatedUpdateCell = NULL;
+
+		/*
+		 * Print the notification for each colocated shard as the placement of each colocated
+		 * shard will be updated in the subsequent call.
+		 */
+		foreach(colocatedUpdateCell, colocatedUpdateList)
+		{
+			PlacementUpdateEvent *colocatedUpdate = lfirst(colocatedUpdateCell);
+
+			ereport(NOTICE, (errmsg(
+								 "%s shard %lu from %s:%u to %s:%u ...",
+								 noticeOperation,
+								 colocatedUpdate->shardId,
+								 colocatedUpdate->sourceNode->workerName,
+								 colocatedUpdate->sourceNode->workerPort,
+								 colocatedUpdate->targetNode->workerName,
+								 colocatedUpdate->targetNode->workerPort
+								 )));
+		}
 		UpdateShardPlacement(placementUpdate, responsiveWorkerList,
 							 shardReplicationModeOid);
 		MemoryContextReset(localContext);

src/test/regress/expected/shard_rebalancer.out

@@ -1776,6 +1776,8 @@ DETAIL:  The balance improvement of 0.1xxxxx is lower than the improvement_thres
 NOTICE:  Ignored 1 moves, all of which are shown in notices above
 HINT:  If you do want these moves to happen, try changing improvement_threshold to a lower value than what it is now (0.5).
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
  rebalance_table_shards
 ---------------------------------------------------------------------
@@ -2805,6 +2807,8 @@ select 1 from citus_add_node('localhost', :worker_2_port);
 (1 row)
 
 select rebalance_table_shards();
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
  rebalance_table_shards
 ---------------------------------------------------------------------
@@ -2905,6 +2909,8 @@ SELECT sh.logicalrelid, pl.nodeport
 -- but because the coordinator is not allowed for shards, rebalancer will distribute each colocation group to both workers
 select rebalance_table_shards(shard_transfer_mode:='block_writes');
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
  rebalance_table_shards
 ---------------------------------------------------------------------

src/test/regress/expected/single_node_enterprise.out

@@ -244,6 +244,7 @@ DROP TABLE statement_replicated;
 -- and the other in block_writes
 SELECT rebalance_table_shards(max_shard_moves:=1);
 NOTICE:  Stopped searching before we were out of moves. Please rerun the rebalancer after it's finished for a more optimal placement.
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
  rebalance_table_shards
 ---------------------------------------------------------------------
@@ -252,6 +253,8 @@ NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
 
 SELECT rebalance_table_shards(shard_transfer_mode:='block_writes');
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
  rebalance_table_shards
 ---------------------------------------------------------------------
@@ -417,6 +420,9 @@ SET citus.shard_replication_factor TO 1;
 SELECT master_drain_node('localhost', :master_port, shard_transfer_mode:='block_writes');
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
+NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
 NOTICE:  Moving shard xxxxx from localhost:xxxxx to localhost:xxxxx ...
  master_drain_node
 ---------------------------------------------------------------------