public CommandProcessorResponse compileAndRespond(String command, boolean cleanupTxnList)
      throws CommandProcessorException {
    try {
      compileInternal(command, false);
      return new CommandProcessorResponse(getSchema(), null);
    } catch (CommandProcessorException cpe) {
      saveErrorMessageAndRethrow(cpe);
      return null;
    } finally {
      if (cleanupTxnList) {
        // Valid txn list might be generated for a query compiled using this command, thus we need to reset it
        driverTxnHandler.cleanupTxnList();
      }
    }
  }
Checks if the recorded snapshot is up-to-date
ql/src/java/org/apache/hadoop/hive/ql/Driver.java