[ARROW-16005] [Java] JDBC-to-Arrow: Arrays do not work with ArrowVectorIterator

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 7.0.0
• Fix Version/s: 9.0.0
• Component/s: Java
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/31428
• Assignee: Thomas Powell
• Reporter: Thomas Powell
• Created: 22/Mar/22 16:13
• Updated: 11/Jan/23 11:41
• Resolved: 01/Jun/22 20:54

Description

ArrowVectorIterator does not currently work with arrays.

One issue is that initializing the ArrayConsumer requires ListVector#getDataVector but currently this is called before the VectorSchemaRoot is initialized so there is no ListVector to pass: https://github.com/apache/arrow/blob/master/java/adapter/jdbc/src/main/java/org/apache/arrow/adapter/jdbc/ArrowVectorIterator.java#L76. 

Caused by: java.lang.NullPointerException: Cannot invoke "org.apache.arrow.vector.complex.ListVector.getDataVector()" because "vector" is null
    at org.apache.arrow.adapter.jdbc.JdbcToArrowUtils.getConsumer(JdbcToArrowUtils.java:432)
    at org.apache.arrow.adapter.jdbc.ArrowVectorIterator.initialize(ArrowVectorIterator.java:74)
    at org.apache.arrow.adapter.jdbc.ArrowVectorIterator.create(ArrowVectorIterator.java:91)
    ... 72 more 

A second issue comes when there are multiple batches. ArrayConsumer#resetValueVector does not currently do anything with the delegate. As a result, ListVector#dataVector does not have its index reset which is an issue when reusing the VectorSchemaRoot. 

Issue Links

• links to: GitHub Pull Request #12692