extern "C" a_sql_uint32 ( SQL_CALLBACK *entry-point-function )( a_init_pre_filter *data );

1 on error and 0 on successful execution

This function must be implemented in the external prefilter library, and needs to be re-entrant as it can be executed on multiple threads simultaneously.

The caller of the function (database server) provides a pointer to an a_text_source object that serves as the producer for the prefilter. The caller also provides the character set of the input.

This function provides a pointer to the external prefilter (a_text_source structure). It also negotiates the character set of the input (if it is not binary) and output data by changing the actual_charset field, if necessary.

If desired_charset and actual_charset are not the same, the database server performs character set conversion on the input data, unless data->is_binary field is 1. If is_binary is 0, input data is in the character set specified by actual_charset.

Requiring character set conversion can cause a degradation in performance.

This entry point function is specified by the user by calling ALTER TEXT CONFIGURATION...PREFILTER EXTERNAL NAME.

• a_init_pre_filter structure
• a_init_pre_filter structure
• a_text_source interface
• PREFILTER EXTERNAL NAME clause, ALTER TEXT CONFIGURATION statement