feat: allow lazily chunking unsorted iteration #55
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pmarks
reviewed
Sep 4, 2024
src/lib.rs
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| // Check that the skip_lazy feature produces the expected results. | ||
| let mut unsorted_reader_skip = UnsortedShardReader::<T1>::open(tmp.path()); | ||
| let to_skip = (disk_chunk_size * 3) + 1; |
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maybe scramble this value somehow to get different boundaries, or try a few different carefully chosen skip values here? You could skip to a file boundary, a chunk boundary, or the middle of a chunk and ideally the tests would hit all 3 cases?
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I ultimately didn't merge the cellranger patch that made use of this feature, so I'm a bit on the fence about merging it at all at this point.
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Looking into this again now.
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I enhanced the tests by writing two shard files of size n_items, to test the set reading logic. I expanded the skip tests to include these offsets:
check_unsorted_skip(0)?;
check_unsorted_skip(1)?;
check_unsorted_skip(disk_chunk_size)?;
check_unsorted_skip((disk_chunk_size * 3) + 1)?;
check_unsorted_skip(n_items)?; // skip entire first file
check_unsorted_skip(n_items + 1)?; // skip entire first file plus next item
check_unsorted_skip(n_items * 2)?; // skip everything
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Refactors unsorted shard iteration into a few more granular types.
Adds a
skip_lazymethod to the top-level type to allow lazily seeking into a collection of shard files. This allows chunking a set of shard files for parallel unordered iteration by multiple readers without having to read anything more than the shard index plus the first partially-read shard.