@Override
    protected IrRowPattern visitIrConcatenation(IrConcatenation node, Void context) {
      List<IrRowPattern> children =
          node.getPatterns().stream().map(this::process).collect(toImmutableList());

      return new IrConcatenation(children);
    }
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