CREATE TABLE test_table (Id Int32, Foo Int32) ENGINE = MergeTree ORDER BY Id;

CREATE TABLE test_table_merge AS test_table ENGINE = Merge(currentDatabase(), 'test_table');

INSERT INTO test_table (Id, Foo) VALUES (1, 1);

-- Left table has Merge engine
SELECT any(t2.Foo)
FROM test_table_merge AS t1
LEFT JOIN test_table AS t2 ON t1.Id = t2.Id
GROUP BY t1.Id

/*
Received exception from server (version 20.8.5):
Code: 10. DB::Exception: Received from clickhouse-server:9000. DB::Exception: Not found column t2.Foo in block. There are only columns: Id.

0 rows in set. Elapsed: 0.003 sec.
*/

-- Left table hasn't Merge engine
SELECT any(t2.Foo)
FROM test_table AS t1
LEFT JOIN test_table AS t2 ON t1.Id = t2.Id
GROUP BY t1.Id

/*
┌─any(t2.Foo)─┐
│           1 │
└─────────────┘

1 rows in set. Elapsed: 0.016 sec.
*/

-- Left table has Merge engine
SELECT any(t2.Foo)
FROM test_table_merge AS t1
LEFT JOIN test_table AS t2 ON t1.Id = t2.Id
GROUP BY t1.Id

/*
Received exception from server (version 20.12.3):
Code: 47. DB::Exception: Received from clickhouse-server:9000. DB::Exception: Unknown identifier (in aggregate function 'any'): t2.Foo.

0 rows in set. Elapsed: 0.003 sec.
*/

-- Left table hasn't Merge engine
SELECT any(t2.Foo)
FROM test_table AS t1
LEFT JOIN test_table AS t2 ON t1.Id = t2.Id
GROUP BY t1.Id

/*
┌─any(t2.Foo)─┐
│           1 │
└─────────────┘

1 rows in set. Elapsed: 0.013 sec.
*/