private void beforeParsing() throws MetaException {
      if (!onParsing && !filterBuilder.getFilter().isEmpty()) {
        filterBuilder.append(" && ");
      }
      onParsing = true;
    }
Generate the JDOQL filter for the given expression tree
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/parser/ExpressionTree.java