AdamGS commented on code in PR #17808:
URL: https://github.com/apache/datafusion/pull/17808#discussion_r2387744827
##########
datafusion/expr-common/src/type_coercion/binary.rs:
##########
@@ -955,28 +974,111 @@ pub fn decimal_coercion(lhs_type: &DataType, rhs_type:
&DataType) -> Option<Data
match (lhs_type, rhs_type) {
// Prefer decimal data type over floating point for comparison
operation
+ (Decimal32(_, _), Decimal32(_, _)) => get_wider_decimal_type(lhs_type,
rhs_type),
+ (Decimal32(_, _), Decimal64(_, _) | Decimal128(_, _) | Decimal256(_,
_)) => {
+ get_wider_decimal_type_cross_variant(lhs_type, rhs_type)
+ }
+ (Decimal32(_, _), _) => get_common_decimal_type(lhs_type, rhs_type),
+ (Decimal64(_, _), Decimal64(_, _)) => get_wider_decimal_type(lhs_type,
rhs_type),
+ (Decimal64(_, _), Decimal32(_, _) | Decimal128(_, _) | Decimal256(_,
_)) => {
+ get_wider_decimal_type_cross_variant(lhs_type, rhs_type)
+ }
+ (Decimal64(_, _), _) => get_common_decimal_type(lhs_type, rhs_type),
(Decimal128(_, _), Decimal128(_, _)) => {
get_wider_decimal_type(lhs_type, rhs_type)
}
+ (Decimal128(_, _), Decimal32(_, _) | Decimal64(_, _) | Decimal256(_,
_)) => {
+ get_wider_decimal_type_cross_variant(lhs_type, rhs_type)
+ }
(Decimal128(_, _), _) => get_common_decimal_type(lhs_type, rhs_type),
- (_, Decimal128(_, _)) => get_common_decimal_type(rhs_type, lhs_type),
(Decimal256(_, _), Decimal256(_, _)) => {
get_wider_decimal_type(lhs_type, rhs_type)
}
+ (Decimal256(_, _), Decimal32(_, _) | Decimal64(_, _) | Decimal128(_,
_)) => {
+ get_wider_decimal_type_cross_variant(lhs_type, rhs_type)
+ }
(Decimal256(_, _), _) => get_common_decimal_type(lhs_type, rhs_type),
+ (_, Decimal32(_, _)) => get_common_decimal_type(rhs_type, lhs_type),
+ (_, Decimal64(_, _)) => get_common_decimal_type(rhs_type, lhs_type),
+ (_, Decimal128(_, _)) => get_common_decimal_type(rhs_type, lhs_type),
(_, Decimal256(_, _)) => get_common_decimal_type(rhs_type, lhs_type),
(_, _) => None,
}
}
+/// Handle cross-variant decimal widening by choosing the larger variant
+fn get_wider_decimal_type_cross_variant(
+ lhs_type: &DataType,
+ rhs_type: &DataType,
+) -> Option<DataType> {
+ use arrow::datatypes::DataType::*;
+
+ let (p1, s1) = match lhs_type {
+ Decimal32(p, s) => (*p, *s),
+ Decimal64(p, s) => (*p, *s),
+ Decimal128(p, s) => (*p, *s),
+ Decimal256(p, s) => (*p, *s),
+ _ => return None,
+ };
+
+ let (p2, s2) = match rhs_type {
+ Decimal32(p, s) => (*p, *s),
+ Decimal64(p, s) => (*p, *s),
+ Decimal128(p, s) => (*p, *s),
+ Decimal256(p, s) => (*p, *s),
+ _ => return None,
+ };
+
+ // max(s1, s2) + max(p1-s1, p2-s2), max(s1, s2)
+ let s = s1.max(s2);
+ let range = (p1 as i8 - s1).max(p2 as i8 - s2);
+ let required_precision = (range + s) as u8;
+
+ // We currently don't handle cases where the required precision overflows
+ if required_precision > DECIMAL256_MAX_PRECISION {
+ return None;
+ }
+
+ // Choose the larger variant between the two input types
+ match (lhs_type, rhs_type) {
+ (Decimal32(_, _), Decimal64(_, _)) | (Decimal64(_, _), Decimal32(_,
_)) => {
+ Some(Decimal64(required_precision, s))
+ }
+ (Decimal32(_, _), Decimal128(_, _)) | (Decimal128(_, _), Decimal32(_,
_)) => {
+ Some(Decimal128(required_precision, s))
+ }
+ (Decimal32(_, _), Decimal256(_, _)) | (Decimal256(_, _), Decimal32(_,
_)) => {
+ Some(Decimal256(required_precision, s))
+ }
+ (Decimal64(_, _), Decimal128(_, _)) | (Decimal128(_, _), Decimal64(_,
_)) => {
+ Some(Decimal128(required_precision, s))
+ }
+ (Decimal64(_, _), Decimal256(_, _)) | (Decimal256(_, _), Decimal64(_,
_)) => {
+ Some(Decimal256(required_precision, s))
+ }
+ (Decimal128(_, _), Decimal256(_, _)) | (Decimal256(_, _),
Decimal128(_, _)) => {
+ Some(Decimal256(required_precision, s))
+ }
Review Comment:
I'll add some tests to make sure what's the correct thing here is.
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