@Override
            public Optional<PrimitiveConverter> visit(DecimalLogicalTypeAnnotation logicalTypeAnnotation) {
              return Optional.of(EDECIMAL_CONVERTER.getConverter(type, index, parent, hiveTypeInfo));
            }
ETypeConverter is an easy way to set the converter for the right type.
ql/src/java/org/apache/hadoop/hive/ql/io/parquet/convert/ETypeConverter.java