@Override
    public long getFileBytes(int column, WriterEncryptionVariant writerEncryptionVariant) {
      long size = 0L;
      List<CacheOutputReceiver> l = this.colStreams.get(column);
      if (l == null) {
        return size;
      }
      for (CacheOutputReceiver c : l) {
        if (c.getData() != null && !c.suppressed && c.getName().getArea() != StreamName.Area.INDEX) {
          for (MemoryBuffer buffer : c.getData()) {
            size += buffer.getByteBufferRaw().limit();
          }
        }
      }
      return size;
    }
For !doesSourceHaveIncludes case, stores global column IDs to verify writer columns.
For doesSourceHaveIncludes case, stores source column IDs used to map things.
llap-server/src/java/org/apache/hadoop/hive/llap/io/encoded/SerDeEncodedDataReader.java