presto-main/src/main/java/io/prestosql/sql/planner/EffectivePredicateExtractor.java/Visitor/visitAggregation
class Visitor:        @Override
        public Expression visitAggregation(AggregationNode node, Void context)
        {
            // GROUP BY () always produces a group, regardless of whether there's any
            // input (unlike the case where there are group by keys, which produce
            // no output if there's no input).
            // Therefore, we can't say anything about the effective predicate of the
            // output of such an aggregation.
            if (node.getGroupingKeys().isEmpty()) {
                return TRUE_LITERAL;
            }

            Expression underlyingPredicate = node.getSource().accept(this, context);

            return pullExpressionThroughSymbols(underlyingPredicate, node.getGroupingKeys());
        }