@Override
    protected IrRowPattern visitIrLabel(IrLabel node, Void context) {
      return node;
    }
Remove empty pattern from pattern alternation and replace it with quantification of a
neighbouring term.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/rowpattern/IrPatternAlternationOptimizer.java