James Henderson created ARROW-17107:
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Summary: [Java] JSONFileWriter throws IOOBE writing an empty list
Key: ARROW-17107
URL: https://issues.apache.org/jira/browse/ARROW-17107
Project: Apache Arrow
Issue Type: Bug
Components: Java
Affects Versions: 8.0.0
Reporter: James Henderson
Hey folks,
I'm trying to write an empty ListVector out through the `JsonFileWriter`, and
am getting an IOOBE. Stack trace is as follows:
```
java.lang.IndexOutOfBoundsException: index: 0, length: 4 (expected: range(0, 0))
at org.apache.arrow.memory.ArrowBuf.checkIndexD (ArrowBuf.java:318)
org.apache.arrow.memory.ArrowBuf.chk (ArrowBuf.java:305)
org.apache.arrow.memory.ArrowBuf.getInt (ArrowBuf.java:424)
org.apache.arrow.vector.ipc.JsonFileWriter.writeValueToGenerator
(JsonFileWriter.java:270)
org.apache.arrow.vector.ipc.JsonFileWriter.writeFromVectorIntoJson
(JsonFileWriter.java:237)
org.apache.arrow.vector.ipc.JsonFileWriter.writeFromVectorIntoJson
(JsonFileWriter.java:253)
org.apache.arrow.vector.ipc.JsonFileWriter.writeFromVectorIntoJson
(JsonFileWriter.java:253)
org.apache.arrow.vector.ipc.JsonFileWriter.writeFromVectorIntoJson
(JsonFileWriter.java:253)
org.apache.arrow.vector.ipc.JsonFileWriter.writeBatch
(JsonFileWriter.java:200)
org.apache.arrow.vector.ipc.JsonFileWriter.write (JsonFileWriter.java:190)
```
It's trying to write the offset buffer of the list, which is empty. L224 of
JFW.java sets `bufferValueCount` to 1 (because we're not a DUV), so we enter
the `for` loop. We don't hit the `valueCount=0` condition in L230 (because
we're not a varbinary or a varchar vector). So we fall into the `else`, which
tries to write the 0th element in the offset vector, and IOOBE.
Could we include 'list' in either the L224 or the L230 checks?
Admittedly, I'm not aware of the history of this section, but it seems that, by
the time we hit L230 (i.e. excluding DUV), any empty vector should yield a
single 0?
Let me know if there's any more info I can provide!
Cheers,
James
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