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getNewFieldWriter returns UnionListWriter instead of UnionMapWriter #625

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wsuppiger opened this issue Feb 20, 2025 · 1 comment · May be fixed by #627
Open

getNewFieldWriter returns UnionListWriter instead of UnionMapWriter #625

wsuppiger opened this issue Feb 20, 2025 · 1 comment · May be fixed by #627
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help wanted Extra attention is needed Type: bug Something isn't working

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@wsuppiger
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wsuppiger commented Feb 20, 2025 •
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Not sure if I am using this wrong, but I noticed getNewFieldWriter for the minorType MAP is returning a UnionListWriter instead of a UnionMapWriter.

arrow-java/vector/src/main/java/org/apache/arrow/vector/types/Types.java

Lines 722 to 726 in 799d9fd

@Override
public FieldWriter getNewFieldWriter(ValueVector vector) {
return new UnionListWriter((MapVector) vector);
}
},

This leads to the issue of this code block throwing an error:

writer = MinorType.MAP.getNewFieldWriter(myMapVector)
writer.startMap()

Exception:

You tried to start a map key when you are using a ValueWriter of type UnionListWriter.
java.lang.IllegalStateException: You tried to start a map key when you are using a ValueWriter of type UnionListWriter.
	at org.apache.arrow.vector.complex.impl.AbstractFieldWriter.key(AbstractFieldWriter.java:123)
	at org.apache.arrow.vector.complex.impl.UnionListWriter.key(UnionListWriter.java:69)
...

I believe this code can be easily fixed by just changing it to:

   @Override 
   public FieldWriter getNewFieldWriter(ValueVector vector) { 
     return new UnionMapWriter((MapVector) vector); 
   }
@lidavidm lidavidm added Type: bug Something isn't working help wanted Extra attention is needed labels Feb 20, 2025
@lidavidm
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PRs would be appreciated!

wsuppiger pushed a commit to wsuppiger/arrow-java that referenced this issue Feb 21, 2025
apacheGH-625: Map MinorType getNewFieldWriter returns UnionMapWriter
5dd83f1
@wsuppiger wsuppiger linked a pull request Feb 21, 2025 that will close this issue
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GH-625: Map MinorType getNewFieldWriter returns UnionMapWriter wsuppiger/arrow-java
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@lidavidm @wsuppiger