Proposed Updates to section 2.1#3
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hhhizzz merged 2 commits intohhhizzz:lm-pipeline-blogfrom Dec 7, 2025
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alamb
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Dec 5, 2025
| - **[ReadPlan](https://github.com/apache/arrow-rs/blob/bab30ae3d61509aa8c73db33010844d440226af2/parquet/src/arrow/arrow_reader/read_plan.rs#L302) / [ReadPlanBuilder](https://github.com/apache/arrow-rs/blob/bab30ae3d61509aa8c73db33010844d440226af2/parquet/src/arrow/arrow_reader/read_plan.rs#L34)**: Encodes "which columns to read and with what row subset" into a plan. It does not pre-read all predicate columns. It reads one, tightens the selection, and then moves on. | ||
| - **[RowSelection](https://github.com/apache/arrow-rs/blob/bab30ae3d61509aa8c73db33010844d440226af2/parquet/src/arrow/arrow_reader/selection.rs#L139)**: Describes "skip/select N rows" via RLE (`RowSelector::select/skip`) or a bitmask. This is the core mechanism that carries sparsity through the pipeline. | ||
| - **[ArrayReader](https://github.com/apache/arrow-rs/blob/bab30ae3d61509aa8c73db33010844d440226af2/parquet/src/arrow/array_reader/mod.rs#L85)**: The component responsible for I/O and decoding. It receives a `RowSelection` and decides which pages to read and which values to decode. | ||
| - **[RowSelection](https://github.com/apache/arrow-rs/blob/bab30ae3d61509aa8c73db33010844d440226af2/parquet/src/arrow/arrow_reader/selection.rs#L139)**: Describes "skip/select N rows" using either [Run-length encoding] (RLE) (called a [`RowSelector`]) or a bitmask. This is the core mechanism that carries sparsity through the pipeline. |
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Here is some proposed "wordsmithing" changes for
I'll comment inline with the rationale