Avro adapter: AvroNullableConsumer should use readIndex

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#834 opened on Aug 31, 2025 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 2/5
Estimated time: 1-3 hours
Newbie friendliness: 52/100

Issue type: Bug
Clarity: Clearly specified
Activity status: Stale
Tech stack: java
Domain: backend

Research direction

Start in AvroNullableConsumer.consume, at the readInt call identified in the stack trace, and compare it with Avro's decoder API and ValidatingDecoder behavior. Done means nullable fields can be consumed with a ValidatingDecoder without the union-versus-int exception.

Written by the indexing model from the issue text.

Description

Type: bug

Describe the bug, including details regarding any error messages, version, and platform.

When using Avro's ValidatingDecoder, any schema with a nullable field fails with the following exception:

Exception in thread "main" org.apache.avro.AvroTypeException: Attempt to process a int when a union was expected.
	at org.apache.avro.io.parsing.Parser.advance(Parser.java:91)
	at org.apache.avro.io.ValidatingDecoder.readInt(ValidatingDecoder.java:81)
	at org.apache.arrow.adapter.avro.consumers.AvroNullableConsumer.consume(AvroNullableConsumer.java:44)

Reason: AvroNullableConsumer uses readInt to read the index, but it should use readIndex instead. It's irrelevant in case of a BinaryDecoder, for example (readIndex is the same as readInt), but ValidatingDecoders and any Decoders based on that have different logic.

Dominant language: Java
Stars: 95
Forks: 154
Avg merge: 2d 10h
Merged PRs (30d): 11

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