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Support casting negative scale decimals to numeric #9207

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Merged
alamb merged 6 commits into from
Jan 26, 2026
Merged

Support casting negative scale decimals to numeric #9207

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63b042c
feat: upport casting negative scale decimals to numeric
Chiicake Jan 17, 2026
8a14788
fix: pull the check out of hot loop
Chiicake Jan 17, 2026
7033f0c
fix: add more tests
Chiicake Jan 17, 2026
42b092c
fix: clippy check of too complex type
Chiicake Jan 18, 2026
03d045f
fix: remove the type alias
Chiicake Jan 20, 2026
bd9ce61
fix: cargo fmt
Chiicake Jan 20, 2026
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21 changes: 15 additions & 6 deletions arrow-cast/src/cast/decimal.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -802,6 +802,11 @@ where
}
}

type ScaleOp<D> = fn(
<D as ArrowPrimitiveType>::Native,
<D as ArrowPrimitiveType>::Native,
) -> Result<<D as ArrowPrimitiveType>::Native, ArrowError>;

pub(crate) fn cast_decimal_to_integer<D, T>(
array: &dyn Array,
base: D::Native,
Expand All @@ -816,7 +821,7 @@ where
{
let array = array.as_primitive::<D>();

let div: D::Native = base.pow_checked(scale as u32).map_err(|_| {
let div: D::Native = base.pow_checked(scale.unsigned_abs() as u32).map_err(|_| {
ArrowError::CastError(format!(
"Cannot cast to {:?}. The scale {} causes overflow.",
D::PREFIX,
Expand All @@ -826,17 +831,21 @@ where

let mut value_builder = PrimitiveBuilder::<T>::with_capacity(array.len());

let scale_op: ScaleOp<D> =
if scale < 0 {
<D::Native as ArrowNativeTypeOp>::mul_checked
} else {
<D::Native as ArrowNativeTypeOp>::div_checked
};

if cast_options.safe {
for i in 0..array.len() {
if array.is_null(i) {
value_builder.append_null();
} else {
let v = array
.value(i)
.div_checked(div)
let v = scale_op(array.value(i), div)
.ok()
.and_then(<T::Native as NumCast>::from::<D::Native>);

value_builder.append_option(v);
}
}
Expand All @@ -845,7 +854,7 @@ where
if array.is_null(i) {
value_builder.append_null();
} else {
let v = array.value(i).div_checked(div)?;
let v = scale_op(array.value(i), div)?;

let value = <T::Native as NumCast>::from::<D::Native>(v).ok_or_else(|| {
ArrowError::CastError(format!(
Expand Down
134 changes: 134 additions & 0 deletions arrow-cast/src/cast/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3886,6 +3886,140 @@ mod tests {
);
}

#[test]
fn test_cast_decimal_to_numeric_negative_scale() {
let value_array: Vec<Option<i256>> = vec![
Some(i256::from_i128(125)),
Some(i256::from_i128(225)),
Some(i256::from_i128(325)),
None,
Some(i256::from_i128(525)),
];
let array = create_decimal256_array(value_array, 38, -1).unwrap();

generate_cast_test_case!(
&array,
Int64Array,
&DataType::Int64,
vec![Some(1_250), Some(2_250), Some(3_250), None, Some(5_250)]
);

let value_array: Vec<Option<i32>> = vec![Some(125), Some(225), Some(325), None, Some(525)];
let array = create_decimal32_array(value_array, 8, -2).unwrap();
generate_cast_test_case!(
&array,
Int64Array,
&DataType::Int64,
vec![Some(12_500), Some(22_500), Some(32_500), None, Some(52_500)]
);

let value_array: Vec<Option<i32>> = vec![Some(2), Some(1), None];
let array = create_decimal32_array(value_array, 9, -9).unwrap();
generate_cast_test_case!(
&array,
Int64Array,
&DataType::Int64,
vec![Some(2_000_000_000), Some(1_000_000_000), None]
);

let value_array: Vec<Option<i64>> = vec![Some(125), Some(225), Some(325), None, Some(525)];
let array = create_decimal64_array(value_array, 18, -3).unwrap();
generate_cast_test_case!(
&array,
Int64Array,
&DataType::Int64,
vec![Some(125_000), Some(225_000), Some(325_000), None, Some(525_000)]
);

let value_array: Vec<Option<i64>> = vec![Some(12), Some(34), None];
let array = create_decimal64_array(value_array, 18, -10).unwrap();
generate_cast_test_case!(
&array,
Int64Array,
&DataType::Int64,
vec![Some(120_000_000_000), Some(340_000_000_000), None]
);

let value_array: Vec<Option<i128>> =
vec![Some(125), Some(225), Some(325), None, Some(525)];
let array = create_decimal128_array(value_array, 38, -4).unwrap();
generate_cast_test_case!(
&array,
Int64Array,
&DataType::Int64,
vec![
Some(1_250_000),
Some(2_250_000),
Some(3_250_000),
None,
Some(5_250_000)
]
);

let value_array: Vec<Option<i128>> = vec![Some(9), Some(1), None];
let array = create_decimal128_array(value_array, 38, -18).unwrap();
generate_cast_test_case!(
&array,
Int64Array,
&DataType::Int64,
vec![
Some(9_000_000_000_000_000_000),
Some(1_000_000_000_000_000_000),
None
]
);

let array = create_decimal32_array(vec![Some(999_999_999)], 9, -1).unwrap();
let casted_array = cast_with_options(
&array,
&DataType::Int64,
&CastOptions {
safe: false,
format_options: FormatOptions::default(),
},
);
assert_eq!(
"Arithmetic overflow: Overflow happened on: 999999999 * 10".to_string(),
casted_array.unwrap_err().to_string()
);

let casted_array = cast_with_options(
&array,
&DataType::Int64,
&CastOptions {
safe: true,
format_options: FormatOptions::default(),
},
);
assert!(casted_array.is_ok());
assert!(casted_array.unwrap().is_null(0));

let array = create_decimal64_array(vec![Some(13)], 18, -1).unwrap();
let casted_array = cast_with_options(
&array,
&DataType::Int8,
&CastOptions {
safe: false,
format_options: FormatOptions::default(),
},
);
assert_eq!(
"Cast error: value of 130 is out of range Int8".to_string(),
casted_array.unwrap_err().to_string()
);

let casted_array = cast_with_options(
&array,
&DataType::Int8,
&CastOptions {
safe: true,
format_options: FormatOptions::default(),
},
);
assert!(casted_array.is_ok());
assert!(casted_array.unwrap().is_null(0));
}

#[test]
fn test_cast_numeric_to_decimal128() {
let decimal_type = DataType::Decimal128(38, 6);
Expand Down