How to reproduce:
WITH (
SELECT arrayResize([1], 1000000)
) AS arr
SELECT length(arr)
Query id: 60eaa526-a0e3-4a56-a54b-75f0e26c6606
┌─length(arr)─┐
1. │ 1000000 │
└─────────────┘
1 row in set. Elapsed: 0.967 sec.
SET allow_experimental_analyzer = 0
Query id: 357f9028-abdf-4d1d-9875-69e4ac0f2af7
Ok.
0 rows in set. Elapsed: 0.001 sec.
WITH (
SELECT arrayResize([1], 1000000)
) AS arr
SELECT length(arr)
Query id: e35bd81a-36cd-427c-aeec-916ff20cb7c6
┌─length(arr)─┐
1. │ 1000000 │
└─────────────┘
1 row in set. Elapsed: 0.011 sec.
Flamegraph shows:

How to reproduce:
WITH ( SELECT arrayResize([1], 1000000) ) AS arr SELECT length(arr) Query id: 60eaa526-a0e3-4a56-a54b-75f0e26c6606 ┌─length(arr)─┐ 1. │ 1000000 │ └─────────────┘ 1 row in set. Elapsed: 0.967 sec. SET allow_experimental_analyzer = 0 Query id: 357f9028-abdf-4d1d-9875-69e4ac0f2af7 Ok. 0 rows in set. Elapsed: 0.001 sec. WITH ( SELECT arrayResize([1], 1000000) ) AS arr SELECT length(arr) Query id: e35bd81a-36cd-427c-aeec-916ff20cb7c6 ┌─length(arr)─┐ 1. │ 1000000 │ └─────────────┘ 1 row in set. Elapsed: 0.011 sec.Flamegraph shows:
