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Unify the Parquet dictionary value decoders #23612

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yingsu00 opened this issue Sep 10, 2024 · 1 comment
Open

Unify the Parquet dictionary value decoders #23612

yingsu00 opened this issue Sep 10, 2024 · 1 comment

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@yingsu00
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There are many dictionary ID value decoders in the Parquet batch reader. They usually allocates a buffer in every readNext call and it is bad for reliability and performance. There is no need to create a separate decoder and add unnecessary memory allocation and memory copies. It would be nice to send a new PR to unify existing RLE dictionary decoders. After all, dictionary IDs can only be RLE/BP encoded, and is not relevant to the data column types.

Ref: https://parquet.apache.org/docs/file-format/data-pages/encodings/
"Data page format: the bit width used to encode the entry ids stored as 1 byte (max bit width = 32), followed by the values encoded using RLE/Bit packed described above (with the given bit width)."

See #23584

@yingsu00
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cc @ethanyzhang

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