haohuaijin commented on code in PR #10702:
URL: https://github.com/apache/arrow-rs/pull/10702#discussion_r3812316565
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parquet/src/arrow/push_decoder/mod.rs:
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@@ -249,6 +250,55 @@ impl ParquetPushDecoderBuilder {
}
}
+ /// Select row groups and rows using row-group-local coordinates.
+ ///
+ /// Entries are decoded in the supplied order, and omitted row groups are
+ /// skipped. A row group listed more than once is decoded once per entry.
+ /// A `None` selection reads the entire row group. A selection shorter
+ /// than its row group skips the trailing rows, while a selection longer
+ /// than its row group returns an error from [`Self::build`]. Each
+ /// selection is passed through without being re-partitioned, so no
+ /// conversion between the bitmap and selector representations is forced
+ /// (how the selection is then materialized while reading is still governed
+ /// by [`ArrowReaderBuilder::with_row_selection_policy`]).
+ ///
+ /// [`ArrowReaderBuilder::with_offset`] and
+ /// [`ArrowReaderBuilder::with_limit`] apply after the row-group-local
+ /// selections and any [`ArrowReaderBuilder::with_row_filter`], across the
+ /// plan as a whole and in the supplied order: the offset skips the first N
+ /// remaining rows and the limit caps the total rows emitted, regardless of
+ /// which row group they come from.
+ ///
+ /// This configuration is mutually exclusive with
+ /// [`ArrowReaderBuilder::with_row_groups`] and
+ /// [`ArrowReaderBuilder::with_row_selection`]. Combining them returns an
+ /// error from [`Self::build`]. Calling this method more than once replaces
+ /// the previous row-group-local configuration.
+ ///
+ /// ```no_run
Review Comment:
i added some docs to explain this, thank you.
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