fix: Parquet column writer Dictionary(_, Decimal128) and Dictionary(_, Decimal256)
#6987
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korowa
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etseidl
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Jan 16, 2025
| @@ -270,6 +270,59 @@ where | |||
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| Arc::new(array) as ArrayRef | |||
| } | |||
| ArrowType::Dictionary(_, value_type) => match value_type.as_ref() { | |||
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This looks correct to me. It would be nice if we could get some code reuse here.
| @@ -2670,6 +2712,52 @@ mod tests { | |||
| one_column_roundtrip_with_schema(Arc::new(d), schema); | |||
| } | |||
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| #[test] | |||
| fn arrow_writer_decimal128_dictionary() { | |||
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Verified that tests fail if the read changes are reverted.
etseidl
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Jan 16, 2025
| } | ||
| .with_precision_and_scale(*p, *s)?; | ||
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| arrow_cast::cast(&array, target_type)? |
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Taking a second look, I'm curious why the cast here rather than creating the ArrayRef directly as is done above? Will this have any performance implications?
Edit: ah, ok. We need to cast to dictionary. Disregard 😅
alamb
changed the title
Dictionary(_, Decimal128) and Dictionary(_, Decimal256)
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Which issue does this PR close?
Closes #.
Rationale for this change
Currently Parquet reads/writes for Arrow
Dictionary(Decimal)type where Decimal is INT-based is falling back toarrow_cast::cast, which leads to losing precision.What changes are included in this PR?
For
Dictionary(Decimal)type where decimal is int-based, writer and reader now performarrow_cast::castonly for dictionary packing/unpacking, while values are only casted to required integer type without being modified, similar to how regularDecimalworks.Are there any user-facing changes?
No