private int getScale(PrimitiveType type) {
              DecimalLogicalTypeAnnotation logicalType = (DecimalLogicalTypeAnnotation) type.getLogicalTypeAnnotation();
              return logicalType.getScale();
            }
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