presto-main/src/main/java/io/prestosql/sql/relational/SqlToRowExpressionTranslator.java/Visitor/visitCoalesceExpression
class Visitor:        @Override
        protected RowExpression visitCoalesceExpression(CoalesceExpression node, Void context)
        {
            List<RowExpression> arguments = node.getOperands().stream()
                    .map(value -> process(value, context))
                    .collect(toImmutableList());

            return new SpecialForm(COALESCE, getType(node), arguments);
        }