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[Java] MapVector written data does not meet expectations #40
Description
What would you like help with?
RootAllocator allocator = new RootAllocator(Long.MAX_VALUE);
Map<String, String> metadata = new HashMap<>();
metadata.put("K1", "V1");
metadata.put("K2", "V2");
Field a = new Field("key", FieldType.notNullable(new ArrowType.Int(32, true)), null);
Field b = new Field("value", FieldType.nullable(new ArrowType.Int(32,true)), null);
Schema schema = new Schema(asList(a, b), metadata);
Field struct = new Field("struct", FieldType.notNullable(new ArrowType.Struct()), schema.getFields());
StructVector structVector = new StructVector(Field.nullable("struct", struct.getType()), allocator, null);
MapVector mapVector = new MapVector(Field.nullable("map", structVector.getField().getType()), allocator, null);
mapVector.initializeChildrenFromFields(Collections.singletonList(struct));
mapVector.allocateNew();
UnionMapWriter writer = mapVector.getWriter();
for (int i = 0; i < 10; i++) {
writer.startMap();
writer.setPosition(i);
writer.key().writeInt(i);
writer.value().writeInt(i * 10);
writer.endMap();
}
writer.setValueCount(10);
when the types of key and value are different, data cannot be written .
Only examples of ListVector are available in the documentation on the official website ,Please provide an example of writing data to MapVector.
Activity
[-][Java] MapVector write demo[/-][+][Java] MapVector written data does not meet expectations[/+]lidavidm commentedon Nov 6, 2024
I think this belongs on apache/arrow and not apache/arrow-adbc?
hawk9821 commentedon Nov 7, 2024
yes , here are the dependencies , version is
15.0.1hawk9821 commentedon Nov 12, 2024
@lidavidm hi, whether the community has a plan to provide the correct MapVector example
lidavidm commentedon Nov 25, 2024
@hawk9821 sorry for the delay, if I can find some time I will try to add a Cookbook example
yashdotdev13 commentedon Nov 14, 2026
Hi @lidavidm,
I've opened PR #1475 with a MapVector usage example.
The example demonstrates creating a MapVector with BIGINT keys and INT values, writing multiple key-value entries using UnionMapWriter, and reading them back using UnionMapReader.
I hope this helps clarify the expected usage of MapVector. Feedback and suggestions are welcome. Thanks!