Mysql: MySQL Workbench 6.3 and the Options File editor

Yeah, today it wrote the query_cache_wlock_invalidate (boolean) parameter to the my.cnf file and forgot to give it some value.

You won't believe what happened next... MySQL did not woke up after the restart... FML

C, MySQL: A minimal UDF

An example, how to start writing an UDF for MySQL.

#include <stdio.h>
#include <string.h>

#include <mysql/my_global.h>
#include <mysql/my_sys.h>
#include <mysql/mysql.h>
#include <mysql/m_ctype.h>
#include <mysql/m_string.h>

#define UUID_LEN 36
#define FMASK "%36s"
#define UUID "/proc/sys/kernel/random/uuid"

my_bool newid_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
void new_deinit(UDF_INIT *initid);
char *newid(UDF_INIT *initid, UDF_ARGS *args, char *result, unsigned long *length, char *is_null, char *error);

my_bool newid_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
{
    if (args->arg_count != 0 || args->arg_type[0] != STRING_RESULT)
    {
        strcpy(message, "Wrong arguments to newid; Use the source");
        return 1;
    }
    initid->max_length=UUID_LEN;
    return 0;
}

void newid_deinit(UDF_INIT *initid)
{
//
}

char *newid(UDF_INIT *initid, UDF_ARGS *args, char *result, unsigned long *length, char *is_null, char *error)
{
FILE *fp;
char id[UUID_LEN];

    if ((fp = fopen(UUID, "r")) != NULL) {
        fscanf(fp, FMASK, id);
        memcpy(result, id, initid->max_length); // UUID_LEN
        *length = initid->max_length; // UUID_LEN
        *error = 0;
        *is_null = 0;
        return result;
    }
    *is_null = 1;
    *error = 1;
    free(result);
    return NULL;
}

Provides a newid function, which returns an UUID from the kernel's random pool.