public List<PartialPath> getAllTimeSeriesPathInSource() {
    List<ViewExpression> sourceExpressions = new ArrayList<>();
    for (Map.Entry<PartialPath, ViewExpression> entry : this.viewPathToSourceMap.entrySet()) {
      sourceExpressions.add(entry.getValue());
    }
    // for each view expression, get the partial path for time series operand
    List<PartialPath> result = new ArrayList<>();
    GetSourcePathsVisitor getSourcePathsVisitor = new GetSourcePathsVisitor();
    for (ViewExpression expression : sourceExpressions) {
      result.addAll(getSourcePathsVisitor.process(expression, null));
    }
    return result;
  }
This variable will be set in function splitByPartition() according to analysis. And it will be
set when creating new split nodes.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/node/metadata/write/view/CreateLogicalViewNode.java