alamb commented on code in PR #2000:
URL: https://github.com/apache/arrow-rs/pull/2000#discussion_r915181100
##########
arrow/src/array/builder/decimal_builder.rs:
##########
@@ -154,10 +166,59 @@ impl ArrayBuilder for DecimalBuilder {
}
}
+impl Decimal256Builder {
+ /// Creates a new `Decimal256Builder`, `capacity` is the number of bytes
in the values
+ /// array
+ pub fn new(capacity: usize, precision: usize, scale: usize) -> Self {
+ let values_builder = UInt8Builder::new(capacity);
+ let byte_width = 32;
+ Self {
+ builder: FixedSizeListBuilder::new(values_builder, byte_width),
+ precision,
+ scale,
+ }
+ }
+
+ /// Appends a byte slice into the builder.
+ ///
+ /// Automatically calls the `append` method to delimit the slice appended
in as a
+ /// distinct array element.
+ #[inline]
+ pub fn append_value(&mut self, value: &Decimal256) -> Result<()> {
+ let value_as_bytes = value.raw_value();
+
+ if self.builder.value_length() != value_as_bytes.len() as i32 {
Review Comment:
I wonder if we also need to check the `precision` and `scale` of `value`
(and either if they don't match the builder or do conversion if required) 🤔
##########
arrow/src/array/builder/decimal_builder.rs:
##########
@@ -197,4 +258,42 @@ mod tests {
assert_eq!(32, decimal_array.value_offset(2));
assert_eq!(16, decimal_array.value_length());
}
+
+ #[test]
+ fn test_decimal256_builder() {
+ let mut builder = Decimal256Builder::new(30, 40, 6);
+
+ let mut bytes = vec![0; 32];
+ bytes[0..16].clone_from_slice(&8_887_000_000_i128.to_le_bytes());
+ let value = Decimal256::try_new_from_bytes(40, 6,
bytes.as_slice()).unwrap();
+ builder.append_value(&value).unwrap();
+
+ builder.append_null().unwrap();
+
+ bytes = vec![255; 32];
+ let value = Decimal256::try_new_from_bytes(40, 6,
bytes.as_slice()).unwrap();
+ builder.append_value(&value).unwrap();
+
+ bytes = vec![0; 32];
+ bytes[0..16].clone_from_slice(&0_i128.to_le_bytes());
+ bytes[15] = 128;
+ let value = Decimal256::try_new_from_bytes(40, 6,
bytes.as_slice()).unwrap();
Review Comment:
I think we should add a test for appending a `value` that has a
precision/scale other than `40. 6`, as I mentioned above
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