Avro adapter: setPosition doesn't work with BaseVariableWidthVectors

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
java
Domain
data

Research direction

Start by tracing the Avro adapter's Consumer.setPosition behavior with BaseVariableWidthVector-based VarBinaryVector and VarCharVector instances. Reproduce the write sequence 0, 2, 1, 3 and add a regression test; done means positioning no longer erases previously written data or is prevented for these vectors.

Written by the indexing model from the issue text.

Description

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

BaseVariableWidthVector-based vectors (VarBinaryVector, VarCharVector) expect the data to be written sequentially. This means Consumer.setPosition is not safe to use. Imagine the following scenario:

  • write index 0
  • write index 2
  • write index 1
  • write index 3

On the last step, BaseVariableWidthVector.fillHoles erases the data written for the index 2:

  protected final void fillHoles(int index) {
    for (int i = lastSet + 1; i < index; i++) {
      setBytes(i, emptyByteArray, 0, emptyByteArray.length);
    }
    lastSet = index - 1;
  }

Here, index would be 3, lastSet + 1 would be 2 (1 + 1), so setBytes(2, emptyByteArray, ...) is called.

Not sure what the right solution is here, but at a minimum, the library shouldn't allow calling setPosition for Consumers using BaseVariableWidthVector vectors.

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

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