jayzhan211 commented on code in PR #10268:
URL: https://github.com/apache/datafusion/pull/10268#discussion_r1593511241
##########
datafusion/sqllogictest/test_files/coalesce.slt:
##########
@@ -209,28 +209,20 @@ select
[3, 4] List(Field { name: "item", data_type: Int64, nullable: true, dict_id:
0, dict_is_ordered: false, metadata: {} })
# TODO: after switch signature of array to the same with coalesce, this query
should be fixed
-query ?T
+query error
select
coalesce(array[1, 2], array[arrow_cast(3, 'Int32'), arrow_cast(4, 'Int32')]),
arrow_typeof(coalesce(array[1, 2], array[arrow_cast(3, 'Int32'),
arrow_cast(4, 'Int32')]));
-----
-[1, 2] List(Field { name: "item", data_type: Int64, nullable: true, dict_id:
0, dict_is_ordered: false, metadata: {} })
statement ok
create table test1 as values (arrow_cast('foo', 'Dictionary(Int32, Utf8)')),
(null);
# Dictionary and String are not coercible
-query ?
+query error
Review Comment:
I recently met an similar issue in moving aggregate function where they have
their owned coercion rule, specifically `Sum` and `Avg`.
https://github.com/apache/datafusion/blob/96487ea0cbb7901a1e4aa18fdf6deb8961319fea/datafusion/expr/src/type_coercion/aggregates.rs#L108-L149
I think we need to have function-specific coercion. Introduce
TypeSignature::coercion, and it calls `fn coerce_types` for udf, udaf function
in `coerce_arguments_for_signature`. We can then have different coercion rule
for coalesce, make_array, sum, avg, and more. This not only solve the issue
above and also for UDAF. The user can define their coercion rule too.
What do you think? @alamb
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