[erlang-questions] Erlang and MySQL: ODBC, Column type not supported

[Hanfei Shen]

Hi Ingela,

Did you mean the value of variable "sql_type"?

I tried to inspect it through gdb, setting a break on func
encode_data_type. And then I got:

Breakpoint 1, encode_data_type (sql_type=-9, size=255,
decimal_digits=0, state=0x7fffc657ec40) at odbcserver.c:1396
1396        switch(sql_type) {


2011/5/2 Ingela Andin <ingela@REDACTED>:
> Hi!
>
> The erlang odbc application supports {sql-varchars,  N} where N = 255
> in your case. The return values
> you get suggest that the odbc-driver you have returns an unexpected column type.
>
> In the erlang odbc port program there is a switch that handles type
> when describing a coloumn that if we take out
> the handling code looks like this.
>
> switch(sql_type) {
>    case SQL_CHAR:
>    case SQL_VARCHAR:
>    case SQL_WCHAR:
>    case SQL_WVARCHAR:
>    case SQL_NUMERIC:
>    case SQL_DECIMAL:
>    case SQL_INTEGER:
>    case SQL_TINYINT:
>    case SQL_SMALLINT:
>    case SQL_REAL:
>    case SQL_FLOAT:
>    case SQL_DOUBLE:
>    case SQL_BIT:
>    case SQL_TYPE_DATE:
>    case SQL_TYPE_TIME:
>    case SQL_TYPE_TIMESTAMP:
>    case SQL_BIGINT:
>    case SQL_BINARY:
>    case SQL_LONGVARCHAR:
>    case SQL_VARBINARY:
>    case SQL_LONGVARBINARY:
>    case SQL_INTERVAL_MONTH:
>    case SQL_INTERVAL_YEAR:
>    case SQL_INTERVAL_DAY:
>    case SQL_INTERVAL_MINUTE:
>    case SQL_INTERVAL_HOUR_TO_SECOND:
>    case SQL_INTERVAL_MINUTE_TO_SECOND:
>    case SQL_UNKNOWN_TYPE:
>    default: /* Will probably never happen */
>        ei_x_encode_atom(&dynamic_buffer(state), "ODBC_UNSUPPORTED_TYPE");
>        break;
>    }
>
>
> And you end up in the default clause which is very unexpected and the
> root to your problem.  If  you can figur out
> what your driver returns for the ODBC C-API function SQLDescribeCol we
> could know if the driver is at fault or if the odbc-port program is.
>
> Regards  Ingela Erlang/OTP team - Ericsson AB
>
> 2011/5/1 Hanfei Shen <qqshfox@REDACTED>:
>> Dear all,
>>
>> I'm a newbie programming in erlang. When I used ODBC to connect to a
>> MySQL database through Connector/ODBC (MyODBC), I got some error when
>> calling odbc:sql_query(Conn, "SELECT * FROM action"):
>>
>> {error,"Column type not supported"}
>>
>> Then I call odbc:describe_table(Conn, "action"), it returned:
>>
>> {ok,[{"id",sql_integer},
>>      {"code",'ODBC_UNSUPPORTED_TYPE'},
>>      {"compliment_desc",'ODBC_UNSUPPORTED_TYPE'},
>>      {"status_desc",'ODBC_UNSUPPORTED_TYPE'},
>>      {"parameter",'ODBC_UNSUPPORTED_TYPE'},
>>      {"cause",'ODBC_UNSUPPORTED_TYPE'},
>>      {"disabled",sql_tinyint}]}
>>
>> And desc the table in mysql client:
>> mysql> desc action;
>> +-----------------+--------------+------+-----+---------+----------------+
>> | Field           | Type         | Null | Key | Default | Extra          |
>> +-----------------+--------------+------+-----+---------+----------------+
>> | id              | int(11)      | NO   | PRI | NULL    | auto_increment |
>> | code            | varchar(255) | NO   |     | NULL    |                |
>> | compliment_desc | varchar(255) | NO   |     |         |                |
>> | status_desc     | varchar(255) | NO   |     |         |                |
>> | parameter       | varchar(255) | NO   |     |         |                |
>> | cause           | varchar(255) | NO   | UNI |         |                |
>> | disabled        | tinyint(1)   | NO   |     | 0       |                |
>> +-----------------+--------------+------+-----+---------+----------------+
>>
>> It seems that Erlang ODBC driver does not support the mysql type
>> varchar? How can I use the database without touching the db schema?
>>
>>
>> Some details about the system env:
>>
>> $ uname -a
>> Linux 2.6.36-gentoo-r8 #4 SMP Thu Apr 7 20:13:18 CST 2011 x86_64
>> Intel(R) Core(TM)2 Duo CPU E7500 @ 2.93GHz GenuineIntel GNU/Linux
>>
>> $ erl
>> Erlang R13B04 (erts-5.7.5) [source] [64-bit] [smp:2:2] [rq:2]
>> [async-threads:0] [kernel-poll:false]
>>
>> $ emerge -vp erlang
>> dev-lang/erlang-13.2.4  USE="doc kpoll odbc smp ssl -emacs -hipe -java
>> -sctp -tk -wxwidgets"
>>
>> eshell> code:which(odbc).
>> "/usr/lib64/erlang/lib/odbc-2.10.7/ebin/odbc.beam"
>>
>> $ mysql -V
>> mysql  Ver 14.14 Distrib 5.1.51, for pc-linux-gnu (x86_64) using readline 5.1
>>
>> Server version: 5.1.51-log Gentoo Linux mysql-5.1.51
>>
>> $ emerge -vp myodbc
>> dev-db/myodbc-5.1.6  USE="-debug -doc -qt4 -static"
>>
>>
>> Any help will be greatly appreciated.  Thanks in advance.
>> Sorry for my poor English, I'm not a native...
>>
>> Best,
>>
>> --
>> Hanfei
>> _______________________________________________
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>>
>