protected boolean containsAggregate(Expression condition) {
            return condition.find(e -> e instanceof AggregateExpression) != null;
        }
This rule finds aggregate expressions that are not in an aggregate operator.  For example,
those in a HAVING clause or ORDER BY clause.  These expressions are pushed down to the
underlying aggregate operator and then projected away after the original operator.
indexr-query-opt/src/main/java/io/indexr/query/Analyzer.java