With sum for example: sumMerge accepts sumState instead of sum

[alsugiliazova]

create table t (a Int32) engine= MergeTree order by tuple();

insert into t values (3), (4);

select hex(sumState(a)) from t;

SELECT sumMerge(CAST(unhex('0700000000000000'), 'AggregateFunction(sumState, Int32)'));

24.8 output:

0700000000000000
7

I expect to see (behavior before 22.8):

Code: 43. DB::Exception: Received from localhost:9000. DB::Exception: Illegal type AggregateFunction(sumState, Int32) of argument for aggregate function with Merge suffix, because it corresponds to different aggregate function: sumState instead of sum. (ILLEGAL_TYPE_OF_ARGUMENT)
(query: SELECT sumMerge(CAST(unhex('0700000000000000'), 'AggregateFunction(sumState, Int32)'));)

What had caused this change in behaviour?

[Algunenano]

I don't understand what's unexpected about being able to merge sumState.

[alsugiliazova]

Because you can not have a value of type AggregateFunction(sumState, Int64) as I know. And the state (result of sumState) is from sum function, not from sumState (then it would be sumStateState).

[UnamedRus]

sumState

SELECT toTypeName(sumState(1))

Query id: c65b8646-bd1a-415f-8448-fefa66cb36d9

┌─toTypeName(sumState(1))───────┐
│ AggregateFunction(sum, UInt8) │
└───────────────────────────────┘

[Algunenano]

sumState is the aggregate function state of sum.

[den-crane]

• Normalize AggregateFunction types and state representations #39420