datafusion-contrib / datafusion-contrib/liquid-cache

[Epic] Struct shredding support

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

Description

Very similar (but much simpler) to variant #426

The idea is simple, let's say we have a struct array:

struct Location {
   country: String
   zipcode: Int32
}

And in the sql, we only read the zipcode, SELECT location.zipcode from table, then it makes no sense to cache the entire Location column.

To be fair, the better approach is for DataFusion to only read zipcode column from Parquet. I believe this is been tracked by https://github.com/apache/datafusion/issues/2581

Contributor guide

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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

Start by reviewing the related variant issue #426 and the DataFusion tracking issue #2581 to understand the intended boundaries. Define how projected fields such as location.zipcode should be identified and cached without caching the full struct, then verify the behavior with representative struct-array queries.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
data-engineering
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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