presto-main/src/main/java/io/prestosql/sql/relational/SqlToRowExpressionTranslator.java/SqlToRowExpressionTranslator/visitCharLiteral
class SqlToRowExpressionTranslator:        @Override
        protected RowExpression visitCharLiteral(CharLiteral node, Void context)
        {
            return constant(node.getSlice(), createCharType(node.getValue().length()));
        }