expr: Unify the type infer between frontend and backend

[TennyZhuang]

It's non-trivial, we need some design work.

[xiangjinwu]

I agree we need better ways to align this part between frontend and backend, but they may not be unified into one. For example, the backend may only do interval * float8 and the frontend will add implicit cast when the right hand side is a int2/int4/int8/numeric/float4.

[TennyZhuang]

I agree we need better ways to align this part between frontend and backend, but they may not be unified into one. For example, the backend may only do interval * float8 and the frontend will add implicit cast when the right hand side is a int2/int4/int8/numeric/float4.

In fact, backend can support interval * int16/32/64 #1596, the implicit cast may be avoid? cast has overhead on vectorized execution.

[xiangjinwu]

That also works. But do we intend to avoid inserting implicit cast for all function operands? #1386
Especially, for all functions that accept numbers, do we always generate all combinations?

[wangrunji0408]

Is this done now?

[xiangjinwu]

Is this done now?

Mostly yes, except for some special cases.