public Expression getInnerJoinPredicate() {
      return innerJoinPredicate;
    }
If the expression is EQUAL ComparisonExpression

@return true if the expression is EQUAL ComparisonExpression and leftSymbols contains
    expression.getLeft() and rightSymbols contains expression.getRight().
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/optimizations/JoinUtils.java