pepijnve commented on PR #19321:
URL: https://github.com/apache/datafusion/pull/19321#issuecomment-3660590063
> It makes sense, but I think its fine to use the first type as the hint for
the placeholders - as long as it can be coerced into the unified type when the
placeholders are assigned.
Does this introduce the possibility of deriving too strict a type? In the
current implementation for this example somewhere along the return type is
derived to be `float32`. Does this type inference happen before or after that?
In the case it happens before, the type of the placeholder would be set to
`int64` while you might want it to be `float32` instead.
```
> explain select case a when 0 then ? when 1 then 1::bigint else 2::real end
from values (0),(1),(2) t(a);
+---------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| plan_type | plan
|
+---------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| logical_plan | Projection: CASE t.a WHEN Int64(0) THEN CAST(? AS
Float32) WHEN Int64(1) THEN Float32(1) ELSE Float32(2) END AS CASE t.a WHEN
Int64(0) THEN ? WHEN Int64(1) THEN Int64(1) ELSE Int64(2) END |
| | SubqueryAlias: t
|
| | Projection: column1 AS a
|
| | Values: (Int64(0)), (Int64(1)), (Int64(2))
|
| physical_plan_error | Execution error: Placeholder '?' was not provided a
value for execution.
|
+---------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
```
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