presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/StandardColumnMappings.java/StandardColumnMappings/varcharColumnMapping
class StandardColumnMappings:    public static ColumnMapping varcharColumnMapping(VarcharType varcharType)
    {
        return ColumnMapping.sliceMapping(varcharType, varcharReadFunction(), varcharWriteFunction());
    }