alamb commented on code in PR #2241:
URL: https://github.com/apache/arrow-datafusion/pull/2241#discussion_r851340950
##########
datafusion/physical-expr/src/coercion_rule/binary_rule.rs:
##########
@@ -178,15 +178,30 @@ fn get_comparison_common_decimal_type(
}
};
match (decimal_type, &other_decimal_type) {
- (DataType::Decimal(p1, s1), DataType::Decimal(p2, s2)) => {
- let new_precision = p1.max(p2);
- let new_scale = s1.max(s2);
- Some(DataType::Decimal(*new_precision, *new_scale))
+ (d1 @ DataType::Decimal(_, _), d2 @ DataType::Decimal(_, _)) => {
+ get_wider_decimal_type(d1, d2)
}
_ => None,
}
}
+// Find the winder decimal type when both types are decimal.
Review Comment:
```suggestion
// Returns a `DataType::Decimal` that can store any value from either
// `lhs_decimal_type` and `rhs_decimal_type`
```
##########
datafusion/physical-expr/src/coercion_rule/binary_rule.rs:
##########
@@ -178,15 +178,30 @@ fn get_comparison_common_decimal_type(
}
};
match (decimal_type, &other_decimal_type) {
- (DataType::Decimal(p1, s1), DataType::Decimal(p2, s2)) => {
- let new_precision = p1.max(p2);
- let new_scale = s1.max(s2);
- Some(DataType::Decimal(*new_precision, *new_scale))
+ (d1 @ DataType::Decimal(_, _), d2 @ DataType::Decimal(_, _)) => {
+ get_wider_decimal_type(d1, d2)
}
_ => None,
}
}
+// Find the winder decimal type when both types are decimal.
+// The result decimal type is (max(s1, s2) + max(p1-s1, p2-s2), max(s1, s2)).
+fn get_wider_decimal_type(
+ lhs_decimal_type: &DataType,
+ rhs_type: &DataType,
+) -> Option<DataType> {
+ match (lhs_decimal_type, rhs_type) {
+ (DataType::Decimal(p1, s1), DataType::Decimal(p2, s2)) => {
+ // max(s1, s2) + max(p1-s1, p2-s2), max(s1, s2)
+ let s = *s1.max(s2);
+ let range = (p1 - s1).max(p2 - s2);
Review Comment:
👍 I see that the precision includes the scale 👍
##########
datafusion/physical-expr/src/coercion_rule/binary_rule.rs:
##########
@@ -557,15 +571,17 @@ mod tests {
DataType::Float32,
DataType::Float64,
DataType::Decimal(38, 10),
+ DataType::Decimal(20, 8),
];
let result_types = [
DataType::Decimal(20, 3),
DataType::Decimal(20, 3),
DataType::Decimal(20, 3),
- DataType::Decimal(20, 3),
- DataType::Decimal(20, 7),
- DataType::Decimal(30, 15),
+ DataType::Decimal(23, 3),
+ DataType::Decimal(24, 7),
+ DataType::Decimal(32, 15),
DataType::Decimal(38, 10),
+ DataType::Decimal(25, 8),
Review Comment:
👍
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