parquet: decoder-level dictionary filter pushdown for Parquet reader#9464
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parquet: decoder-level dictionary filter pushdown for Parquet reader#9464lyang24 wants to merge 1 commit intoapache:mainfrom
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Push predicate evaluation into the decoder for dictionary-encoded BYTE_ARRAY columns. Instead of decoding all rows into StringViewArray and then filtering, this evaluates the predicate once on the small dictionary (~N unique values), then maps integer keys to booleans via a simple lookup — no intermediate arrays are created for data rows. Two-phase approach: - Phase 1: decode dictionary page, evaluate predicate, produce matching_keys: Vec<bool> per row group - Phase 2: DictFilterDecoder reads RLE-encoded integer keys and maps each key to matching_keys[key], producing a BooleanArray that feeds directly into RowSelection Adds ArrowPredicate::use_dictionary_encoding() opt-in flag and falls back to the normal path for multi-column predicates, non-BYTE_ARRAY types, nested columns, or PLAIN-encoded pages.
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Which issue does this PR close?
Rationale for this change
for columns that is dictionary encoded
we use to turn dictionary encoding into StringViewArray then we compare against the filter
What changes are included in this PR?
for a column that is 100% dictionary encoded
we decode the dictionary keys, then apply filter, then expand the nulls, at last we filter the value and only materialize those who survived the filter.
Are these changes tested?
existing test should pass added additional tests
Are there any user-facing changes?
yes added an new api with_dict_pushdown to opt in to enable the predicate pushdown on predicates