Block structure mismatch in UnionStep stream: different number of columns when projections are used with JOIN

[antonio2368]

How to reproduce

CREATE TABLE t1 (id UInt32, s String) Engine = MergeTree ORDER BY id;

CREATE TABLE t2 (id1 UInt32, id2 UInt32) Engine = MergeTree ORDER BY id1;
INSERT INTO t2 SELECT * from generateRandom() LIMIT 100;
ALTER TABLE t2 ADD PROJECTION proj (SELECT id2 ORDER BY id2);
INSERT INTO t2 SELECT * from generateRandom() LIMIT 100;

SELECT s FROM t1 as lhs LEFT JOIN (SELECT * FROM t2 WHERER id2 = 1) as rhs ON lhs.id = rhs.id2;

Received exception from server (version 23.11.1):
Code: 49. DB::Exception: Received from localhost:9000. DB::Exception: Block structure mismatch in UnionStep stream: different number of columns:
id2 UInt32 UInt32(size = 0)
id UInt32 UInt32(size = 0), s String String(size = 0). (LOGICAL_ERROR)

cc @amosbird anything familiar?

[amosbird]

It's not reproduceable in current master. Do you have some special settings enabled?

[antonio2368]

Sorry, it's not reproduceable by my example, noticed right now I made a change that skipped this check:

 if (candidate.sum_marks >= ordinary_reading_marks)
    continue;

Do you have an idea how to modify my test case to pass this check without any modification to the code?

Regardless of that, we noticed this issue happening on our release builds so it's a real problem.

[amosbird]

Do you have an idea how to modify my test case to pass this check without any modification to the code?

SELECT s
FROM t1 AS lhs
LEFT JOIN
(
    SELECT *
    FROM t2
    WHERE id2 = 1
) AS rhs ON lhs.id = rhs.id2

This one can reproduce. I will investigate.