public void discardData() {
      LlapIoImpl.LOG.debug("Discarding disk data (if any wasn't cached)");
      for (CacheStripeData stripe : stripes) {
        if (stripe.colStreams == null || stripe.colStreams.isEmpty()) continue;
        for (List<CacheStreamData> streams : stripe.colStreams.values()) {
          for (CacheStreamData cos : streams) {
            for (MemoryBuffer buffer : cos.data) {
              if (LlapIoImpl.CACHE_LOGGER.isTraceEnabled()) {
                LlapIoImpl.CACHE_LOGGER.trace("Deallocating " + buffer);
              }
              bufferManager.getAllocator().deallocate(buffer);
            }
          }
        }
        stripe.colStreams.clear();
      }
    }
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