mysql中的select @@version

有些朋友問過的問題，mysql中查詢版本號，有的是5.7.18，有的是 5.7.18-log ，有的是5.7.18-debug,如下

mysql> select @@version;
+------------------+
| @@version        |
+------------------+
| 5.7.18-debug-log |
+------------------+
1 row in set (34.23 sec)

mysql> select @@version;
+------------------+
| @@version        |
+------------------+
| 5.7.18-log       |
+------------------+
1 row in set (1 min 27.10 sec)

mysql> select @@version;
+------------------+
| @@version        |
+------------------+
| 5.7.18           |
+------------------+
1 row in set (1 min 27.10 sec)

這其實跟mysqld的編譯選項和啓動參數相關，代碼如下

main
    mysqld_main(int, char**)
        init_common_variables()
            set_server_version()

邏輯就在函數set_server_version()中,可以看到，在嵌入式中，還有可能是-embedded.

/*
  Create version name for running mysqld version
  We automaticly add suffixes -debug, -embedded, -log, -valgrind and -asan
  to the version name to make the version more descriptive.
  (MYSQL_SERVER_SUFFIX is set by the compilation environment)
*/

static void set_server_version(void)
{
  char *end= strxmov(server_version, MYSQL_SERVER_VERSION,
                     MYSQL_SERVER_SUFFIX_STR, NullS);
#ifdef EMBEDDED_LIBRARY
  end= my_stpcpy(end, "-embedded");
#endif
#ifndef DBUG_OFF
  if (!strstr(MYSQL_SERVER_SUFFIX_STR, "-debug"))
    end= my_stpcpy(end, "-debug");
#endif
  if (opt_general_log || opt_slow_log || opt_bin_log)
    end= my_stpcpy(end, "-log");          // This may slow down system
#ifdef HAVE_VALGRIND
  if (SERVER_VERSION_LENGTH - (end - server_version) >
      static_cast<int>(sizeof("-valgrind")))
    end= my_stpcpy(end, "-valgrind"); 
#endif
#ifdef HAVE_ASAN
  if (SERVER_VERSION_LENGTH - (end - server_version) >
      static_cast<int>(sizeof("-asan")))
    end= my_stpcpy(end, "-asan");
#endif
}