Describe the unexpected behaviour

"Unexpected inf or nan to integer conversion" error is thrown when calling toInt32 on the result of an if expression that checks for isNaN and evaulates to NULL.

How to reproduce

• Which ClickHouse server version to use: 21.12.4 revision 54452 & 22.2.2 revision 54455

• Which interface to use, if matters: clickhouse-client

• Non-default settings, if any: none

• CREATE TABLE statements for all tables involved

create temporary table tmp_repro_nan_check (
  foo Nullable(Int32)
);

• Sample data for all these tables, use [clickhouse-obfuscator]

insert into tmp_repro_nan_check values (nan);

• Queries to run that lead to unexpected result

SELECT toInt32(if(isNaN(foo), NULL, foo))
FROM tmp_repro_nan_check

Expected behavior

Expect the result to be NULL similar to the following:

SELECT toInt32(NULL)

Error message and/or stacktrace

Code: 70. DB::Exception: Received from localhost:9000. DB::Exception: Unexpected inf or nan to integer conversion: while executing 'FUNCTION toInt32(if(isNaN(foo), NULL, foo) :: 3) -> toInt32(if(isNaN(foo), NULL, foo)) Nullable(Int32) : 0'. (CANNOT_CONVERT_TYPE)

Additional context

There seems to be an issues with returning NULL in the truthy/left branch of the condition. Updating the select statement to return 0 does not throw an error

SELECT toInt32(if(isNaN(foo), 0, foo))
FROM tmp_repro_nan_check

Query id: 6f91e2e3-caf2-4aa8-96a0-83bd6755ca37

┌─toInt32(if(isNaN(foo), 0, foo))─┐
│                               0 │
└─────────────────────────────────┘