2025-05-29 kernel meeting notes

[zachschuermann]

Summary

0.11.0 released!!

current PRs

• scan incremental API from @roeap
  • any implications from compactions? nope. strictly optimization
  • is there any overlap? ListedLogFiles, etc. maybe
• log compactions from @nicklan
• IN/NOT IN PR to merge @roeap (waiting on opaque expressions. then will go in to default engine)
• predicate/expressions split @scovich - merging lots of PRs
• !!!! opaque expressions @scovich
  • arrow opaque expressions need another level of indirection
  • need an 'arrow expression'
• (won't do) merge IN/NOT IN deprecation @zachschuermann
• #[derive(IntoEngineData)] (zach)
• CRC in logsegment
• test only sync engine
• orphan rule (KernelTryFrom)
• HDFS (check with tyler) removal
• bunch of timestamp work from @OussamaSaoudi

POC/waiting PRs

• CREATE TABLE (zach)
• Crate split (deprio)

upcoming

• zach: metrics PR!
• zach: ActionsBatch struct PR
• need row id's (re-introduce predicate pushdown)
• @hntd187 targeting CDF reads, need timestamp work
• stats for writes (doing simple non-default engine for now): per-table write metadata schema
• CRC visitor
• CRC P+M optimization on reads
• kyjah: ask for SHALLOW CLONE in kernel - size/scope?
• prefactor: remove a scan-wide physical schema and push down to something that can access parquet footer
• remove execute, do default engine execute
• robert: working on support for multiple object stores?
• zach: prioritize DAT more?
• zach: FileIO/Evaluation split
  • nick/ryan: we could colocate EvaluationHandler stuff as a CPU-bound zone (and FileIO layer all IO-bound/blocking)
  • maybe call out: EngineData should be in memory

Attendees

@zachschuermann @nicklan @scovich @mightyshazam @joonyoo181 @hntd187

notes stream

• aurora was 10x faster in rust lol
• metrics are hard
• careful: kernel can't aggregate metrics from batches bc e.g. you could run batches in parallel! then "addition" isn't correct.
  • counts could be easy?
  • duration is hard - scheduling. IO/wall clock time? etc.
• pass context to engine for them to populate
• context + how to accumulate?