public static boolean predicateCanPushDownToSource(Expression predicate) {
    return new PredicateCanPushDownToSourceChecker().process(predicate, null);
  }
Check if the given predicate can be pushed down from FilterNode to ScanNode.

<p>The predicate <b>cannot</b> be pushed down if it satisfies the following conditions:
<li>predicate contains IS_NULL

@param predicate given predicate
@return true if the given predicate can be pushed down to source
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/analyze/PredicateUtils.java