datafusion-contrib / datafusion-contrib/orc-rust

Dictionary array handling

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enhancement low
Dominant language
Rust
Stars
30
Forks
26
Avg merge
19m
Merged PRs (30d)
3

Description

Spun off from discussion in https://github.com/datafusion-contrib/datafusion-orc/pull/68

Find way to preserve dictionary encoding in DictionaryArray without having to cast to StringArray as introduced here:

https://github.com/datafusion-contrib/datafusion-orc/blob/bb885c03cfedb4d4e16d0203b90a9789463e2fb7/src/arrow_reader/decoder/string.rs#L180-L183

Some reference from similar parquet issue: https://github.com/apache/arrow-rs/issues/171

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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 with src/arrow_reader/decoder/string.rs around lines 180-183, where the linked issue introduced the cast to StringArray. Read the referenced Apache Arrow issue and the linked pull request discussion to understand the desired DictionaryArray behavior. Done means dictionary encoding is preserved without that cast.

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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