datafusion-contrib / datafusion-contrib/liquid-cache

Support cache pass-through for selective scans

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#485 2 comments 1 reaction 0 assignees View on GitHub

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Dominant language
Rust
Stars
452
Forks
51
Avg merge
3h 10m
Merged PRs (30d)
12

Description

It would be useful to have a way to selectively pass through certain scans without caching.
When working with a mix of small and large datasets, caching everything can cause the t4 file to grow significantly (decoded Arrow batches are ~5x larger than compressed parquet). This leads to memory pressure and degrades cache
lookup performance for smaller datasets that benefit most from caching.

Having a way to control this — for example, a size threshold, a predicate callback, or a configuration option — would allow large datasets (GBs) to pass through without entering the cache, while smaller frequently-accessed data continues to be cached effectively in mixed workloads.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

No files, tests, or entry points are named. Start by locating the scan and cache insertion paths, then determine how a size threshold, predicate callback, or configuration option should control pass-through behavior. Done means large selected scans bypass caching while smaller datasets retain effective caching without excessive cache growth.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
data-engineering, performance
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
38/100

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