presto-main/src/main/java/io/prestosql/sql/relational/SqlToRowExpressionTranslator.java/SqlToRowExpressionTranslator/visitSubscriptExpression
class SqlToRowExpressionTranslator:        @Override
        protected RowExpression visitSubscriptExpression(SubscriptExpression node, Void context)
        {
            RowExpression base = process(node.getBase(), context);
            RowExpression index = process(node.getIndex(), context);

            return call(
                    metadata.resolveOperator(SUBSCRIPT, ImmutableList.of(base.getType(), index.getType())),
                    getType(node),
                    base,
                    index);
        }