private static void printDirCacheEntries() {
    if (dirCache != null) {
      LOG.debug("Cache entries: {}", Arrays.toString(dirCache.asMap().keySet().toArray()));
    }
  }
Determines transaction type based on query AST.
@param tree AST
ql/src/java/org/apache/hadoop/hive/ql/io/AcidUtils.java