Count(*) returns empty response when there are no segments

[rohityadav1993]

when doing a select count(*) from table_name query on a table with no segments, the response is empty instead of 0.

This is a correct behavour for non aggregation queries but for general aggregation queries where datatype is known a default value like 0 can be returned, e.g. sum(), count(), etc when there are no segments otherwise the caller needs to handle the empty rows scenario as well to prevent result parsing failures.

I'll be happy to contribute if we can get a confirmation if this is an intended behavior or can be improved.

[ankitsultana]

I agree we should fix this and it's been a long standing annoyance.

FYI: we had found a somewhat related issue early on in the MSE: #10124, though in that case we were returning empty result-set even when the table had data.

[Jackie-Jiang]

This is the same as #13057