apache / apache/arrow-java

[Java][arrow-jdbc] Ability to customize JdbcConsumer construction

Open
#224 1 comment 0 reactions 0 assignees View on GitHub
Type: enhancement
Dominant language
Java
Stars
94
Forks
152
Avg merge
3d 16h
Merged PRs (30d)
11

Description

### Describe the enhancement requested

I'm working on a project that heavily uses the arrow-jdbc library to convert results from a number of different JDBC drivers to Arrow. When the integration was initially written a bit over 2 years ago it forked `ArrowVectorIterator` to add a number of customization points in the JDBC->Arrow conversion which were missing at the time. I'm updating the project and happily in the intervening time it looks like a lot of this customization is now possible natively via customization points in `JdbcToArrowConfig` - in particular the ability to override `JdbcFieldInfo` per column and most importantly the ability to override a `Function`.

I'd love to fully remove our forked `ArrowVectorIterator` but there's one last customization point we're depending on that I don't see a way to handle currently: The ability to customize the `JdbcConsumer` instances constructed for each column. We depend on overriding these to paper over idiosyncrasies with various JDBC drivers. As an example on the top of my mind this morning: The Snowflake JDBC driver [does not support](https://docs.snowflake.com/en/user-guide/jdbc-api.html#id14) `getBinaryStream` and so is not compatible with the default `BinaryConsumer` and must be overriden with a consumer that uses `getBytes` instead. We also add a layer of wrapping to all of our `JdbcConsumers` to wrap error messages to aid debugging (by adding info on the specific column an error originated from).

Would it be possible to add an extension point to the `JdbcToArrowConfig` to customize this, similar to `jdbcToArrowTypeConverter`? I wish we didn't need it but in practice we've found enough variability across JDBC drivers to necessitate it.

### Component(s)

Java

Contributor guide

Open the contributing guide

Research direction

Start by reading ArrowVectorIterator and JdbcToArrowConfig, then trace how JdbcConsumer instances are constructed for each column. Define an extension point analogous to jdbcToArrowTypeConverter that permits driver-specific consumers and wrapping, and verify that the Snowflake getBytes workaround can be supplied through it.

Written by the indexing model from the issue text.

Assessment

Tech stack
java
Domain
databases
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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