presto-hive/src/main/java/io/prestosql/plugin/hive/util/HiveBucketingV2.java/HiveBucketingV2/hashOfMap
class HiveBucketingV2:    private static int hashOfMap(MapTypeInfo type, Block singleMapBlock)
    {
        TypeInfo keyTypeInfo = type.getMapKeyTypeInfo();
        TypeInfo valueTypeInfo = type.getMapValueTypeInfo();
        int result = 0;
        for (int i = 0; i < singleMapBlock.getPositionCount(); i += 2) {
            // Sic! we're hashing map keys with v2 but map values with v1 just as in
            // https://github.com/apache/hive/blob/7dc47faddba9f079bbe2698aaa4d8712e7654f87/serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/ObjectInspectorUtils.java#L903-L904
            result += hash(keyTypeInfo, singleMapBlock, i) ^ HiveBucketingV1.hash(valueTypeInfo, singleMapBlock, i + 1);
        }
        return result;
    }