private void validateFileMetadata() throws IOException {
    if (fileMetadata.getCompressionKind() == CompressionKind.NONE) return;
    int bufferSize = fileMetadata.getCompressionBufferSize();
    long minAllocSize = HiveConf.getSizeVar(daemonConf, ConfVars.LLAP_ALLOCATOR_MIN_ALLOC);
    if (bufferSize < minAllocSize) {
      LOG.warn("ORC compression buffer size (" + bufferSize + ") is smaller than LLAP low-level "
            + "cache minimum allocation size (" + minAllocSize + "). Decrease the value for "
            + HiveConf.ConfVars.LLAP_ALLOCATOR_MIN_ALLOC.toString() + " to avoid wasting memory");
    }
  }
stripeRgs[stripeIx'] => boolean array (could be a bitmask) of rg-s that need to be read.
Contains only stripes that are read, and only columns included. null => read all RGs.
llap-server/src/java/org/apache/hadoop/hive/llap/io/encoded/OrcEncodedDataReader.java