apache / apache/arrow-java

[Java] Enhancements for Java Dataset API

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#154 1 comment 0 reactions 0 assignees View on GitHub
Dominant language
Java
Stars
94
Forks
152
Avg merge
3d 16h
Merged PRs (30d)
11

Description

### Describe the enhancement requested

Some important changes are suggested in the list below to improve the developer experience with the Dataset API of java/arrow. Most of these suggestions if implemented will lead to consistency with the [pyarrow dataset API](https://arrow.apache.org/docs/python/generated/pyarrow.dataset.dataset.html#pyarrow.dataset.dataset).

1. Support for providing Filesystem options like access_key etc. programmatically. Currently only env vars are supported.
2. Support for globbed paths and directories
3. Excluding invalid files
4. Additional documentation for already implemented functionality
1. Reading and writing to remote/ cloud stores (HDFS, S3, GCS ...)
2. Clarification of behaviour when reading multiple files. Why 2 or more files supplied, they may have different schema. Currently, only the schema of the last files is shown by `.inspect()` and this is not documented anywhere. This behaviour is the same in pyarrow. Maybe it's a good idea to allow users to provide a strategy like Error, Merge, LastFile etc.
3. Reading and writing partitioned datasets
4. Difference between `FileSystemDatasetFactory.inspect()` and `FileSystemDatasetFactory.finish().newScan(...).schema()`. Which one to use in which case?
5. Env vars for Filesystem are not documented

Please let me know if the above make sense, I can help with PRs for the same.

### Component(s)

Java

Contributor guide

Open the contributing guide

Research direction

Start with the Java Dataset API entry points named in the issue, especially FileSystemDatasetFactory.inspect() and finish().newScan(...).schema(). Break the broad requests into separately scoped changes for filesystem options, paths, invalid files, schema behavior, partitioned datasets, and documentation. Done should be defined by an agreed subset with corresponding implementation or documentation and validation.

Written by the indexing model from the issue text.

Assessment

Tech stack
java
Domain
data
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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