Difference between revisions of "OpenDBX/C API/odbx set option"

Revision as of 18:44, 6 May 2007

#include <odbx.h>

int odbx_set_option(
    odbx_t* handle,
    unsigned int option,
    void* value )

Description

Changes the value of the specified option in the backend module or the native database library associated to handle by odbx_init(). Before trying to set an option, it should be tested with odbx_get_option() first to ensure that it is supported by the backend. Almost all options need to be set before connecting to the database server using odbx_bind().

The first parameter handle is the connection object created and returned by odbx_init() which becomes invalid as soon as it was supplied to odbx_finish().

There are several options defined as named constants in the odbx.h header file. The available options whose values can be changed are:

ODBX_OPT_TLS 

Use encryption to transmit all data securely over the network via SSL or TLS. This option can be set to ODBX_TLS_NEVER (the default value) to prevent encrpytion, ODBX_TLS_ALWAYS to enforce encryption and to fail if it can't be used between the client library and the server or ODBX_TLS_TRY to use encryption if possible with the option to fall back to a connection which isn't encrypted.

ODBX_OPT_MULTI_STATEMENTS 

Enables the database server to accept multiple SQL statements in one query string sent via odbx_query() if the value of value is set to one ("1"). Although, it might be possible to disable it by setting it to zero ("0")

ODBX_OPT_PAGED_RESULTS 

All database servers and client libraries are able to transfer the records row by row. Some of them can also transfer multiple rows or even all at once to minimize server load, network traffic and latency. The downside of this is an increased memory consumption. If paged results are supported by the backend, passing positive values fill fetch the specified number of records at once from the database server. The value of zero ("0") is special in this case because it asks the backend module to retrieve all records at once

ODBX_OPT_COMPRESS 

Enable compressed network traffic between database client and server. This can lower the latency if the network is the bottleneck. Pass an integer variable with one ("1") to enable compression or with zero ("0") to disable it for this connection

ODBX_OPT_MODE 

Some database servers support different modes of operation, e.g. modes for compliance to other SQL implementations or completely different query languages. This option is available since OpenDBX 1.1.4. value must point to a zero terminated string and for a detailed description of the MySQL modes look at their website

If not stated otherwise, the type of the variable passed to the third parameter value must be an integer pointer. Its values should be in the range specified by the option being changed.

Return values

odbx_get_option() returns ODBX_ERR_SUCCESS, or an error code whose value is less than zero if one of the operations couldn't be completed successfully. Possible error codes are listed in the error section and they can be feed to odbx_error() and odbx_error_type() to get further details.

Errors

-ODBX_ERR_PARAM 

One of the supplied parameters is invalid or is NULL and this isn't allowed in the used backend module or in the native database client library

-ODBX_ERR_OPTION 

The value passed to the option parameter isn't one of the values listed in this manual. The content of value remains unchanged if this error occurs

-ODBX_ERR_OPTRO 

The option isn't intended for being changed and could only be read via odbx_get_option()

-ODBX_ERR_OPTWR 

Setting the option failed for various reasons. It's most likely that the value passed via value didn't match the range of values expected by the backend or the native database library

See also

• OpenDBX_bind
• OpenDBX_error
• OpenDBX_error_type
• OpenDBX_get_option

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