Function datafusion_expr::binary::type_union_resolution

pub fn type_union_resolution(data_types: &[DataType]) -> Option<DataType>

Coerce dissimilar data types to a single data type. UNION, INTERSECT, EXCEPT, CASE, ARRAY, VALUES, and the GREATEST and LEAST functions are examples that has the similar resolution rules. See https://www.postgresql.org/docs/current/typeconv-union-case.html for more information. The rules in the document provide a clue, but adhering strictly to them doesn’t precisely align with the behavior of Postgres. Therefore, we’ve made slight adjustments to the rules to better match the behavior of both Postgres and DuckDB. For example, we expect adjusted decimal precision and scale when coercing decimal types.