presto-main/src/main/java/io/prestosql/sql/planner/EffectivePredicateExtractor.java/Visitor/visitUnnest
class Visitor:        @Override
        public Expression visitUnnest(UnnestNode node, Void context)
        {
            Expression sourcePredicate = node.getSource().accept(this, context);

            switch (node.getJoinType()) {
                case INNER:
                case LEFT:
                    return pullExpressionThroughSymbols(
                            combineConjuncts(metadata, node.getFilter().orElse(TRUE_LITERAL), sourcePredicate),
                            node.getOutputSymbols());
                case RIGHT:
                case FULL:
                    return TRUE_LITERAL;
                default:
                    throw new UnsupportedOperationException("Unknown UNNEST join type: " + node.getJoinType());
            }
        }