feat(parquet): provide direct access to dictionary pages#10420
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Add sync and async APIs for decoding a BYTE_ARRAY column chunk dictionary page without materializing the full column, enabling exact row-group membership pruning for fully dictionary-encoded chunks. Reuse the regular page reader header, size validation, and decryption path so standalone dictionary decoding handles encrypted, truncated, and malformed pages safely. See apache#9010. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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Which issue does this PR close?
Rationale for this change
This change provides low-level API necessary for enabling dictionary-based pruning in DataFusion: apache/datafusion#23851
What changes are included in this PR?
parquet::file::metadata::dictionary::decode_dictionary_page: decodesa BYTE_ARRAY dictionary page (Thrift header parse, decompress, PLAIN
decode) into a
Utf8/BinaryArrow array.ParquetMetaDataReader::read_column_dictionary(sync) andread_column_dictionary_async(async) to fetch and decode a given row group/column's dictionary page from aParquetMetaData, returningOk(None)if the chunk has no dictionary page.ParquetRecordBatchStreamBuilder::get_row_group_column_dictionaryconvenience method mirroringget_row_group_column_bloom_filter.Are these changes tested?
Yes: a round-trip unit test for a dictionary-encoded string column, a
non-BYTE_ARRAY rejection test, and sync + async reader tests that
decode a real dictionary page written through
ArrowWriter.Are there any user-facing changes?
Yes, three new public APIs (see above). No changes to
existing API.