scovich commented on code in PR #8540:
URL: https://github.com/apache/arrow-rs/pull/8540#discussion_r2399806680
##########
parquet/src/arrow/schema/primitive.rs:
##########
@@ -132,35 +133,24 @@ fn from_parquet(parquet_type: &Type) -> Result<DataType> {
}
fn decimal_type(scale: i32, precision: i32) -> Result<DataType> {
- if precision <= DECIMAL128_MAX_PRECISION as i32 {
- decimal_128_type(scale, precision)
- } else {
- decimal_256_type(scale, precision)
- }
-}
-
-fn decimal_128_type(scale: i32, precision: i32) -> Result<DataType> {
+ // Convert and validate inputs once
let scale = scale
.try_into()
.map_err(|_| arrow_err!("scale cannot be negative: {}", scale))?;
-
let precision = precision
.try_into()
.map_err(|_| arrow_err!("precision cannot be negative: {}",
precision))?;
- Ok(DataType::Decimal128(precision, scale))
-}
-
-fn decimal_256_type(scale: i32, precision: i32) -> Result<DataType> {
- let scale = scale
- .try_into()
- .map_err(|_| arrow_err!("scale cannot be negative: {}", scale))?;
-
- let precision = precision
- .try_into()
- .map_err(|_| arrow_err!("precision cannot be negative: {}",
precision))?;
-
- Ok(DataType::Decimal256(precision, scale))
+ // Dispatch based on precision thresholds using DecimalType trait constants
+ if precision <= Decimal32Type::MAX_PRECISION {
Review Comment:
What if we added the corrective cast to the `VariantArray` constructor,
which already fixes up the value and metadata columns? The [variant
spec](https://github.com/apache/parquet-format/blob/master/VariantEncoding.md#encoding-types)
arguably requires using the narrowest possible decimal type for a given
precision:
> Decimal Precision | Decimal value type | Variant Physical Type
> -- | -- | --
> 1 <= precision <= 9 | int32 | decimal4
> 10 <= precision <= 18 | int64 | decimal8
> 19 <= precision <= 38 | int128 | decimal16
> | > 38 | Not supported |
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