@Override
  public Pattern<FilterNode> getPattern() {
    return PATTERN;
  }
Rewrite filtering semi-join to inner join.

<p>Transforms:

<pre>
- Filter (semiJoinSymbol AND predicate)
   - SemiJoin (semiJoinSymbol <- (a IN b))
       source: plan A producing symbol a
       filtering source: plan B producing symbol b
</pre>

<p>Into:

<pre>
- Project (semiJoinSymbol <- TRUE)
   - Join INNER on (a = b), joinFilter (predicate with semiJoinSymbol replaced with TRUE)
      - source
      - Aggregation distinct(b)
         - filtering source
</pre>
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/iterative/rule/TransformFilteringSemiJoinToInnerJoin.java