@Override
  public Pattern<TableFunctionNode> getPattern() {
    return PATTERN;
  }
This rule prepares cartesian product of partitions from all inputs of table function.

<p>It rewrites TableFunctionNode with potentially many sources into a TableFunctionProcessorNode.
The new node has one source being a combination of the original sources.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/iterative/rule/ImplementTableFunctionSource.java