arrow-array::builder: support Int8, Int16 and Int64 keys #6845
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alamb
approved these changes
Dec 6, 2024
| Box::new(dict_builder) | ||
| } | ||
| t => panic!("Unsupported dictionary value type {t:?} is not currently supported"), | ||
| DataType::Dictionary(key_type, value_type) if matches!(**key_type, DataType::Int8 | DataType::Int32 ) => { |
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Would it be possible for completeness to also add support for DataType::Int16 and DataType::Int64?
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Heh, I had originally typed it with all of them and backtracked when I read the thread in the initial PR that introduced this code that was concerned with code bloat. Done.
ajwerner
commented
Dec 6, 2024
| Box::new(dict_builder) | ||
| } | ||
| t => panic!("Unsupported dictionary value type {t:?} is not currently supported"), | ||
| DataType::Dictionary(key_type, value_type) if matches!(**key_type, DataType::Int8 | DataType::Int32 ) => { |
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Heh, I had originally typed it with all of them and backtracked when I read the thread in the initial PR that introduced this code that was concerned with code bloat. Done.
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The spec says that the keys in dictionaries are [0]: > (4) The index type of a Dictionary type can only be an integer type, preferably signed, with width 8 to 64 bits. In my use case I have a very small number of values so wasting bits on a wider key is wasteful. [0]: https://github.com/apache/arrow/blob/fe32a7dfe5e22e7737198476fe1ac0e8a5dccef2/docs/source/format/Columnar.rst?plain=1#L182-L183
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Fixed the fmt/clippy issues. |
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Thanks again @ajwerner |
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The spec says that the keys in dictionaries are 0:
In my use case I have a very small number of values so wasting bits on a wider key is wasteful.
Which issue does this PR close?
Closes #6844
Rationale for this change
I have a situation where I have lots of vectors of strings with mostly one string element and at most one per union member -- that means the dictionary keys fit in a single Int8. The builder infrastructure is rather convenient. I can get a solid single-digit reduction in the total size of my batches by using smaller keys.