@Override
  protected Boolean visitTrim(final Trim node, final Void context) {
    return node.getTrimSource().accept(this, context)
        && (!node.getTrimCharacter().isPresent()
            || node.getTrimCharacter().orElse(null).accept(this, context));
  }
only the following predicate will return true: 1. tagColumn = 'XXX' 2. 'XXX' = tagColumn 3.
attributeColumn = 'XXX' 4. 'XXX' = attributeColumn 5. tagColumn/attributeColumn IS NULL 6. using
or to combine the above expression
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/analyzer/predicate/PredicatePushIntoMetadataChecker.java