public static Object buildCacheKey(Object fileId, int schemaHash) {
    if (schemaHash == NO_SCHEMA_HASH) {
      return fileId;
    } else {
      return new SchemaAwareCacheKey(fileId, schemaHash);
    }
  }
Cache key that stores schema hash. Useful caching serdes that do not have a self-describing schema built in.
ql/src/java/org/apache/hadoop/hive/llap/SchemaAwareCacheKey.java