findepi commented on PR #13717:
URL: https://github.com/apache/datafusion/pull/13717#issuecomment-2535985246
> Both of these functions have been part of the public API for a while now.
i believe you
> The newer `return_type_from_exprs` works correctly and the older
`return_type` is incorrect in some cases. It seems better to me to deprecate
the older incorrect version.
date_part's return_type used to be correct in all cases
the implementation was removed because it was no longer correct in all cases
if someone calls `func.return_type()` just for display purposes into logs,
they may be OK getting wrong information.
If someone calls `func.return_type()` and trusts return value, they could be
disappointed if we continue to return something, but the return value doesn't
continue to be correct.
for example (pseudo-code)
```rust
let func_return_value : ArrayRef = ... ;
match func.return_type() {
case Float64 => {
as_float64_array(func_return_value) ...
```
or
```rust
let wanted_type = ...;
let ret func.return_type();
if wanted_type == ret {
return func
} else {
Expr::Cast( func, wanted_type )
}
```
if we need to return some incorrect value for some time, this should be
behind an opt-in config toggle.
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