parthchandra commented on PR #5331:
URL:
https://github.com/apache/datafusion-comet/pull/5331#issuecomment-5259839190
This PR has some followups -
- **Sort keys not in the projection.** Today, if a sort column isn't
selected, we skip the merge and read unordered. Todo: read the sort columns
anyway (even when not selected), merge on them, then drop them before returning.
- **Transform sort orders (bucket/truncate/etc.).** We only handle
plain-column sort orders for now. todo: also handle transformed sort keys,
matching Iceberg's per-type comparison exactly.
- **Read concurrency.** The merge reads files more lazily than today's
unordered read. As a followup benchmark, and if many-small-file reads regress,
read files ahead into small buffers.
- **Single-file partitions.** A partition with one file still gets wrapped
in the merge (a no-op). Skip the wrapper in that case.
- **Storage-partitioned join confidence tests, then default
`reportPartitioning` on.** Add tests for: (a) a heavily skewed key so the
replicate path runs, (b) different bucket counts per side (e.g. bucket(8) vs
bucket(4)) so a partition reducer kicks in, (c) three-way and self joins on the
same key. Once green, flip the flag on by default.
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