Re: [I] parquet: Improve performance of mask/selection construction in `ReadPlanBuilder::with_predicate_options` [arrow-rs]

["alamb (via GitHub)" <gi...@apache.org>]

alamb commented on issue #10776:
URL: https://github.com/apache/arrow-rs/issues/10776#issuecomment-5370325229

   Another example where it might be better to incrementally build the output
   
   ```rust
           // Pad the tail so the filters cover `expected_rows` total. This keeps
           // the invariant that the resulting `RowSelection` spans every row the
           // reader would have produced — rows past the early break are marked
           // "not selected". When no limit is set the loop always exhausts and
           // no padding is needed.
           if let Some(expected) = expected_rows
               && processed_rows < expected
           {
               let pad_len = expected - processed_rows;
               filters.push(BooleanArray::new(BooleanBuffer::new_unset(pad_len), None));
           }
   ```
   
   (it allocates a new array)


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