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DX-66740: GH-36375 [Java] Added creating MapWriter in ComplexWriter. #32

Merged
merged 1 commit into from
Jul 7, 2023
Merged

DX-66740: GH-36375 [Java] Added creating MapWriter in ComplexWriter. #32

merged 1 commit into from
Jul 7, 2023

Commits on Jul 7, 2023

  1. apacheGH-36375: [Java] Added creating MapWriter in ComplexWriter. (ap…

    …ache#36351)
    
    Added new method rootAsMap() to ComplexWriter and implement it in ComplexWriterImpl for supporting map type.
    Previously in dremio side:
    
    When i trying to return map like output ComplexWrite
    with this code:
    
    org.apache.arrow.vector.complex.writer.BaseWriter.MapWriter mapWriter = out.rootAsList().map(false);
    
    mapWriter.startMap();
    for (java.util.Map.Entry<java.lang.Integer, java.lang.Integer> element : map.entrySet()) {
        mapWriter.startEntry();
        mapWriter.key().integer().writeInt((Integer) element.getKey());
        mapWriter.value().integer().writeInt((Integer) element.getValue());
        mapWriter.endEntry();
    }
    mapWriter.endMap();
    It use UnionMapWriter and generate schema like:
    EXPR$0: Map(false)<$data$: Union(Sparse, [1, 39])<struct: Struct<key: Int(32, true) not null, value: Int(32, true) not null> not null, map: Map(false)<entries: Struct<key: Int(32, true) not null, value: Int(32, true)> not null>>>
    But in OutputDerivation impl class where i should create output Complete type
    
    List<Field> children = Arrays.asList( CompleteType.INT.toField("key", false), CompleteType.INT.toField("value", false));
    return new CompleteType(CompleteType.MAP.getType(), CompleteType.struct(children).toField(MapVector.DATA_VECTOR_NAME, false));
    (This is only one valid case, because MapVector.initializeChildrenFromFields())
    return
    EXPR$0::map<key::int32, value::int32> I found a place where it start using union - PromotableWriter.promoteToUnion.
    And in the end i have
    
    SCHEMA_CHANGE ERROR: Schema changed during projection. Schema was 
    schema(EXPR$0::map<key::int32, value::int32>)
     but then changed to 
    schema(EXPR$0::map<struct::struct<key::int32, value::int32>, map::map<key::int32, value::int32>>)
    * Closes: apache#36375
    
    Authored-by: Ivan Chesnov <[email protected]>
    Signed-off-by: David Li <[email protected]>
    xxlaykxx committed Jul 7, 2023
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