Proposed edits to section 2.2#4
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hhhizzz merged 1 commit intohhhizzz:lm-pipeline-blogfrom Dec 7, 2025
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alamb
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Dec 5, 2025
| ### 2.2 Combining row selectors (`RowSelection::and_then`) | ||
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| `RowSelection`—defined in `selection.rs`—is the token that every stage passes around. It mostly uses RLE (`RowSelector::select/skip(len)`) to describe sparse ranges. `and_then` is the core operator for "apply one selection to another": left-hand side is "rows already allowed," right-hand side further filters those rows, and the output is their boolean AND. | ||
| [`RowSelection`] represents the set of rows that will eventually be produced. It currently uses RLE (`RowSelector::select/skip(len)`) to describe sparse ranges. [`RowSelection::and_then`] is the core operator for "apply one selection to another": the left-hand argument is "rows already passed" and the right-hand argument is "which of the passed rows also pass the second filter." The output is their boolean AND. |
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I tried to make it more clear what this code was referring to
alamb
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Dec 5, 2025
| </figure> | ||
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| This keeps narrowing the filter while touching only lightweight metadata—no data copies. The current implementation of `and_then` is a two-pointer linear scan; complexity is linear in selector segments. The sooner predicates shrink the selection, the cheaper later scans become. |
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I propose moving this paragraph below the diagram so the text that describes the diagram is immediately above it
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Here is some proposed "wordsmithing" changes for
I'll comment inline with the rationale