Fix Bug #18559 "log tables cannot change engine, and

                gets deadlocked when dropping w/ log on"

Log tables rely on concurrent insert machinery to add data.
This means that log tables are always opened and locked by
special (artificial) logger threads. Because of this, the thread
which tries to drop a log table starts to wait for the table
to be unlocked. Which will happen only if the log table is disabled.
Alike situation happens if one tries to alter a log table.
However in addition to the problem above, alter table calls
check_if_locking_is_allowed() routine for the engine. The
routine does not allow alter for the log tables. So, alter
doesn't start waiting forever for logs to be disabled, but 
returns with an error.
Another problem is that not all engines could be used for
the log tables. That's because they need concurrent insert.

In this patch we:
(1) Explicitly disallow to drop/alter a log table if it
    is currently used by the logger.
(2) Update MyISAM to support log tables
(3) Allow to drop log tables/alter log tables if log is
    disabled
At the same time we (4) Disallow to alter log tables to
unsupported engine (after this patch CSV and MyISAM are 
alowed)
Recommit with review fixes.


mysql-test/r/log_tables.result:
  Update result file.
  Note: there are warnings in result file. This is because of CSV
  bug (Bug #21328). They should go away after it is fixed.
mysql-test/t/log_tables.test:
  Add a test for the bug
sql/ha_myisam.cc:
  Add log table handling to myisam: as log tables
  use concurrent insert, they are typically
  locked with TL_CONCURRERENT_INSERT lock. So,
  disallow other threads to attempt locking of
  the log tables in incompatible modes. Because
  otherwise the threads will wait for the tables
  to be unlocked forever.
sql/handler.cc:
  Add a function to check if a table we're going to lock
  is a log table and if the lock mode we want allowed
sql/handler.h:
  Add a new function to check compatibility of the locking
sql/log.cc:
  we shouldn't close the log table if and only
  if this particular table is already closed
sql/log.h:
  add new functions to check if a log is enabled
sql/share/errmsg.txt:
  add new error messages
sql/sql_table.cc:
  DROP and ALTER TABLE should not work on log
  tables if the log tables are enabled
storage/csv/ha_tina.cc:
  move function to check if the locking for the log
  tables allowed to handler class, so that we can
  reuse it in other engines.
storage/myisam/mi_extra.c:
  add new ::extra() flag processing to myisam
storage/myisam/mi_open.c:
  init log table flag
storage/myisam/mi_write.c:
  update status after each write if it's a log table
storage/myisam/myisamdef.h:
  Add new log table flag to myisam share.
  We need it to distinguish between usual
  and log tables, as for the log tables we
  should provide concurrent insert in a
  different way than for usual tables: we
  want new rows to be immediately visible
  to other threads.

1 files changed, 141 insertions, 0 deletions

diff --git a/mysql-test/r/log_tables.result b/mysql-test/r/log_tables.result
index c61dd2247ee..f27e4cfc44f 100644
--- a/mysql-test/r/log_tables.result
+++ b/mysql-test/r/log_tables.result
@@ -72,3 +72,144 @@ sleep(2)
 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
+alter table mysql.slow_log engine=myisam;
+ERROR HY000: You can't alter a log table if logging is enabled
+drop table mysql.general_log;
+ERROR HY000: Cannot drop log table if log is enabled
+drop table mysql.slow_log;
+ERROR HY000: Cannot drop log table if log 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
+set global slow_query_log='OFF';
+show create table mysql.general_log;
+Table	Create Table
+general_log	CREATE TABLE `general_log` (
+  `event_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  `user_host` mediumtext,
+  `thread_id` int(11) DEFAULT NULL,
+  `server_id` int(11) DEFAULT NULL,
+  `command_type` varchar(64) DEFAULT NULL,
+  `argument` mediumtext
+) ENGINE=CSV DEFAULT CHARSET=utf8 COMMENT='General log'
+show create table mysql.slow_log;
+Table	Create Table
+slow_log	CREATE TABLE `slow_log` (
+  `start_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  `user_host` mediumtext NOT NULL,
+  `query_time` time NOT NULL,
+  `lock_time` time NOT NULL,
+  `rows_sent` int(11) NOT NULL,
+  `rows_examined` int(11) NOT NULL,
+  `db` varchar(512) DEFAULT NULL,
+  `last_insert_id` int(11) DEFAULT NULL,
+  `insert_id` int(11) DEFAULT NULL,
+  `server_id` int(11) DEFAULT NULL,
+  `sql_text` mediumtext NOT NULL
+) ENGINE=CSV DEFAULT CHARSET=utf8 COMMENT='Slow log'
+alter table mysql.general_log engine=myisam;
+alter table mysql.slow_log engine=myisam;
+Warnings:
+Warning	1264	Out of range value for column 'last_insert_id' at row 0
+Warning	1264	Out of range value for column 'insert_id' at row 0
+show create table mysql.general_log;
+Table	Create Table
+general_log	CREATE TABLE `general_log` (
+  `event_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  `user_host` mediumtext,
+  `thread_id` int(11) DEFAULT NULL,
+  `server_id` int(11) DEFAULT NULL,
+  `command_type` varchar(64) DEFAULT NULL,
+  `argument` mediumtext
+) ENGINE=MyISAM DEFAULT CHARSET=utf8 COMMENT='General log'
+show create table mysql.slow_log;
+Table	Create Table
+slow_log	CREATE TABLE `slow_log` (
+  `start_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  `user_host` mediumtext NOT NULL,
+  `query_time` time NOT NULL,
+  `lock_time` time NOT NULL,
+  `rows_sent` int(11) NOT NULL,
+  `rows_examined` int(11) NOT NULL,
+  `db` varchar(512) DEFAULT NULL,
+  `last_insert_id` int(11) DEFAULT NULL,
+  `insert_id` int(11) DEFAULT NULL,
+  `server_id` int(11) DEFAULT NULL,
+  `sql_text` mediumtext NOT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=utf8 COMMENT='Slow log'
+set global general_log='ON';
+set global slow_query_log='ON';
+select * from mysql.general_log;
+event_time	user_host	thread_id	server_id	command_type	argument
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	set names utf8
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	create table bug16905 (s char(15) character set utf8 default 'пусто')
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	insert into bug16905 values ('новое')
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	select * from mysql.general_log
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	drop table bug16905
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	truncate table mysql.slow_log
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	set session long_query_time=1
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	select sleep(2)
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	select * from mysql.slow_log
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	alter table mysql.general_log engine=myisam
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	alter table mysql.slow_log engine=myisam
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	drop table mysql.general_log
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	drop table mysql.slow_log
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	set global general_log='OFF'
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	set global slow_query_log='ON'
+TIMESTAMP	USER_HOST	THREAD_ID	1	Query	select * from mysql.general_log
+flush logs;
+lock tables mysql.general_log WRITE;
+ERROR HY000: You can't write-lock a log table. Only read access is possible.
+lock tables mysql.slow_log WRITE;
+ERROR HY000: You can't write-lock a log table. Only read access is possible.
+lock tables mysql.general_log READ;
+ERROR HY000: You can't use usual read lock with log tables. Try READ LOCAL instead.
+lock tables mysql.slow_log READ;
+ERROR HY000: You can't use usual read lock with log tables. Try READ LOCAL instead.
+lock tables mysql.slow_log READ LOCAL, mysql.general_log READ LOCAL;
+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
+alter table mysql.slow_log engine=innodb;
+ERROR HY000: One can use only CSV and MyISAM engines for the log tables
+alter table mysql.slow_log engine=archive;
+ERROR HY000: One can use only CSV and MyISAM engines for the log tables
+alter table mysql.slow_log engine=blackhole;
+ERROR HY000: One can use only CSV and MyISAM engines for the log tables
+drop table mysql.slow_log;
+drop table mysql.general_log;
+drop table mysql.general_log;
+ERROR 42S02: Unknown table 'general_log'
+drop table mysql.slow_log;
+ERROR 42S02: Unknown table 'slow_log'
+use mysql;
+CREATE TABLE `general_log` (
+`event_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
+ON UPDATE CURRENT_TIMESTAMP,
+`user_host` mediumtext,
+`thread_id` int(11) DEFAULT NULL,
+`server_id` int(11) DEFAULT NULL,
+`command_type` varchar(64) DEFAULT NULL,
+`argument` mediumtext
+) ENGINE=CSV DEFAULT CHARSET=utf8 COMMENT='General log';
+CREATE TABLE `slow_log` (
+`start_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
+ON UPDATE CURRENT_TIMESTAMP,
+`user_host` mediumtext NOT NULL,
+`query_time` time NOT NULL,
+`lock_time` time NOT NULL,
+`rows_sent` int(11) NOT NULL,
+`rows_examined` int(11) NOT NULL,
+`db` varchar(512) DEFAULT NULL,
+`last_insert_id` int(11) DEFAULT NULL,
+`insert_id` int(11) DEFAULT NULL,
+`server_id` int(11) DEFAULT NULL,
+`sql_text` mediumtext NOT NULL
+) ENGINE=CSV DEFAULT CHARSET=utf8 COMMENT='Slow log';
+set global general_log='ON';
+set global slow_query_log='ON';
+use test;