Post-review fixes for

Bug #18559 "log tables cannot change engine, and
            gets deadlocked when dropping w/ log on":
1) Add more generic error messages
2) Add new handlerton flag for engines, which support
   log tables
3) Remove (log-tables related) mutex lock in myisam to
   improve performance

mysql-test/r/log_tables.result

@@ -73,16 +73,16 @@ select * from mysql.slow_log;
 start_time	user_host	query_time	lock_time	rows_sent	rows_examined	db	last_insert_id	insert_id	server_id	sql_text
 TIMESTAMP	USER_HOST	QUERY_TIME	00:00:00	1	0	test	0	0	1	select sleep(2)
 alter table mysql.general_log engine=myisam;
-ERROR HY000: You can't alter a log table if logging is enabled
+ERROR HY000: You cannot alter a log table if logging is enabled
 alter table mysql.slow_log engine=myisam;
-ERROR HY000: You can't alter a log table if logging is enabled
+ERROR HY000: You cannot alter a log table if logging is enabled
 drop table mysql.general_log;
-ERROR HY000: Cannot drop log table if log is enabled
+ERROR HY000: You cannot drop a log table if logging is enabled
 drop table mysql.slow_log;
-ERROR HY000: Cannot drop log table if log is enabled
+ERROR HY000: You cannot drop a log table if logging is enabled
 set global general_log='OFF';
 alter table mysql.slow_log engine=myisam;
-ERROR HY000: You can't alter a log table if logging is enabled
+ERROR HY000: You cannot alter a log table if logging is enabled
 set global slow_query_log='OFF';
 show create table mysql.general_log;
 Table	Create Table
@@ -173,13 +173,13 @@ unlock tables;
 set global general_log='OFF';
 set global slow_query_log='OFF';
 alter table mysql.slow_log engine=ndb;
-ERROR HY000: One can use only CSV and MyISAM engines for the log tables
+ERROR HY000: This storage engine cannot be used for log tables"
 alter table mysql.slow_log engine=innodb;
-ERROR HY000: One can use only CSV and MyISAM engines for the log tables
+ERROR HY000: This storage engine cannot be used for log tables"
 alter table mysql.slow_log engine=archive;
-ERROR HY000: One can use only CSV and MyISAM engines for the log tables
+ERROR HY000: This storage engine cannot be used for log tables"
 alter table mysql.slow_log engine=blackhole;
-ERROR HY000: One can use only CSV and MyISAM engines for the log tables
+ERROR HY000: This storage engine cannot be used for log tables"
 drop table mysql.slow_log;
 drop table mysql.general_log;
 drop table mysql.general_log;

mysql-test/t/log_tables.test

@@ -178,21 +178,21 @@ select * from mysql.slow_log;
 
 # check that appropriate error messages are given when one attempts to alter
 # or drop a log tables, while corresponding logs are enabled
---error ER_CANT_ALTER_LOG_TABLE
+--error ER_BAD_LOG_STATEMENT
 alter table mysql.general_log engine=myisam;
---error ER_CANT_ALTER_LOG_TABLE
+--error ER_BAD_LOG_STATEMENT
 alter table mysql.slow_log engine=myisam;
 
---error ER_CANT_DROP_LOG_TABLE
+--error ER_BAD_LOG_STATEMENT
 drop table mysql.general_log;
---error ER_CANT_DROP_LOG_TABLE
+--error ER_BAD_LOG_STATEMENT
 drop table mysql.slow_log;
 
 # check that one can alter log tables to MyISAM
 set global general_log='OFF';
 
 # cannot convert another log table
---error ER_CANT_ALTER_LOG_TABLE
+--error ER_BAD_LOG_STATEMENT
 alter table mysql.slow_log engine=myisam;
 
 # alter both tables
@@ -252,13 +252,13 @@ set global general_log='OFF';
 set global slow_query_log='OFF';
 
 # check that alter table doesn't work for other engines
---error ER_BAD_LOG_ENGINE
+--error ER_UNSUPORTED_LOG_ENGINE
 alter table mysql.slow_log engine=ndb;
---error ER_BAD_LOG_ENGINE
+--error ER_UNSUPORTED_LOG_ENGINE
 alter table mysql.slow_log engine=innodb;
---error ER_BAD_LOG_ENGINE
+--error ER_UNSUPORTED_LOG_ENGINE
 alter table mysql.slow_log engine=archive;
---error ER_BAD_LOG_ENGINE
+--error ER_UNSUPORTED_LOG_ENGINE
 alter table mysql.slow_log engine=blackhole;
 
 drop table mysql.slow_log;

sql/handler.h

@@ -681,6 +681,7 @@ struct handlerton
 #define HTON_FLUSH_AFTER_RENAME      (1 << 4)
 #define HTON_NOT_USER_SELECTABLE     (1 << 5)
 #define HTON_TEMPORARY_NOT_SUPPORTED (1 << 6) //Having temporary tables not supported
+#define HTON_SUPPORT_LOG_TABLES      (1 << 7) //Engine supports log tables
 
 typedef struct st_thd_trans
 {

sql/share/errmsg.txt

@@ -5960,3 +5960,7 @@ ER_HOSTNAME
 	eng "host name"
 ER_WRONG_STRING_LENGTH
 	eng "String '%-.70s' is too long for %s (should be no longer than %d)"
+ER_UNSUPORTED_LOG_ENGINE
+        eng "This storage engine cannot be used for log tables""
+ER_BAD_LOG_STATEMENT
+        eng "You cannot %s a log table if logging is enabled"

sql/sql_table.cc

@@ -1628,7 +1628,7 @@ int mysql_rm_table_part2(THD *thd, TABLE_LIST *tables, bool if_exists,
          (!my_strcasecmp(system_charset_info, table->table_name, "slow_log")
           && opt_slow_log && logger.is_slow_log_table_enabled())))
     {
-      my_error(ER_CANT_DROP_LOG_TABLE, MYF(0));
+      my_error(ER_BAD_LOG_STATEMENT, MYF(0), "drop");
       DBUG_RETURN(1);
     }
   }
@@ -5174,7 +5174,7 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
        (table_kind == SLOW_LOG && opt_slow_log &&
          logger.is_slow_log_table_enabled()))
     {
-      my_error(ER_CANT_ALTER_LOG_TABLE, MYF(0));
+      my_error(ER_BAD_LOG_STATEMENT, MYF(0), "alter");
       DBUG_RETURN(TRUE);
     }
 
@@ -5182,10 +5182,9 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
     if ((table_kind == GENERAL_LOG || table_kind == SLOW_LOG) &&
         (lex_create_info->used_fields & HA_CREATE_USED_ENGINE) &&
         (!lex_create_info->db_type || /* unknown engine */
-        !(lex_create_info->db_type->db_type == DB_TYPE_MYISAM ||
-          lex_create_info->db_type->db_type == DB_TYPE_CSV_DB)))
+        !(lex_create_info->db_type->flags & HTON_SUPPORT_LOG_TABLES)))
     {
-      my_error(ER_BAD_LOG_ENGINE, MYF(0));
+      my_error(ER_UNSUPORTED_LOG_ENGINE, MYF(0));
       DBUG_RETURN(TRUE);
     }
   }

storage/csv/ha_tina.cc

@@ -162,7 +162,7 @@ static int tina_init_func()
     tina_hton.db_type= DB_TYPE_CSV_DB;
     tina_hton.create= tina_create_handler;
     tina_hton.panic= tina_end;
-    tina_hton.flags= HTON_CAN_RECREATE;
+    tina_hton.flags= HTON_CAN_RECREATE | HTON_SUPPORT_LOG_TABLES;
   }
   return 0;
 }

storage/myisam/ha_myisam.cc

@@ -1783,7 +1783,7 @@ static int myisam_init()
   myisam_hton.db_type=DB_TYPE_MYISAM;
   myisam_hton.create=myisam_create_handler;
   myisam_hton.panic=mi_panic;
-  myisam_hton.flags=HTON_CAN_RECREATE;
+  myisam_hton.flags= HTON_CAN_RECREATE | HTON_SUPPORT_LOG_TABLES;
   return 0;
 }
 

storage/myisam/mi_write.c

@@ -167,13 +167,13 @@ int mi_write(MI_INFO *info, byte *record)
   /*
     Update status of the table. We need to do so after each row write
     for the log tables, as we want the new row to become visible to
-    other threads as soon as possible. We lock mutex here to follow
-    pthread memory visibility rules.
+    other threads as soon as possible. We don't lock mutex here
+    (as it is required by pthread memory visibility rules) as (1) it's
+    not critical to use outdated share->is_log_table value (2) locking
+    mutex here for every write is too expensive.
   */
-  pthread_mutex_lock(&share->intern_lock);
   if (share->is_log_table)
     mi_update_status((void*) info);
-  pthread_mutex_unlock(&share->intern_lock);
 
   allow_break();				/* Allow SIGHUP & SIGINT */
   DBUG_RETURN(0);