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comparison_coercion

datafusion_expr::binary

Function comparison_coercion 

Source 
pub fn comparison_coercion(
    lhs_type: &DataType,
    rhs_type: &DataType,
) -> Option<DataType>
Expand description

Coerce lhs_type and rhs_type to a common type for comparison contexts — any context where two values are compared rather than unified. This includes binary comparison operators, IN lists, CASE/WHEN conditions, and BETWEEN.

When the two types differ, this function determines the common type to cast to.

§Numeric comparisons

The lower precision type is widened to the higher precision type (e.g., Int32 vs Int64 → Int64).

§Numeric / String comparisons

Prefers the numeric type (e.g., '2' > 1 where 1 is Int32 coerces '2' to Int32).

For type unification contexts (UNION, CASE THEN/ELSE), use type_union_coercion instead.