Fix for Bug #17544 "Cannot do atomic log rotate",

Bug #21785 "Server crashes after rename of the log table" and
Bug #21966 "Strange warnings on create like/repair of the log
            tables"

According to the patch, from now on, one should use RENAME to
perform a log table rotation (this should also be reflected in
the manual).

Here is a sample:

use mysql;
CREATE TABLE IF NOT EXISTS general_log2 LIKE general_log;
RENAME TABLE general_log TO general_log_backup, general_log2 TO general_log;

The rules for Rename of the log tables are following:
      IF   1. Log tables are enabled
      AND  2. Rename operates on the log table and nothing is being
              renamed to the log table.
      DO   3. Throw an error message.
      ELSE 4. Perform rename.
 
The very RENAME query will go the the old (backup) table. This is
consistent with the behavoiur we have with binlog ROTATE LOGS
statement.

Other problems, which are solved by the patch are:

1) Now REPAIR of the log table is exclusive operation (as it should be), this
   also eliminates lock-related warnings. and
2) CREATE LIKE TABLE now usese usual read lock on the source table rather
   then name lock, which is too restrictive. This way we get rid of another
   log table-related warning, which occured because of the above fact
   (as a side-effect, name lock resulted in a warning).


mysql-test/r/log_tables.result:
  update result file
mysql-test/t/log_tables.test:
  Add tests for the bugs
sql/handler.cc:
  update comment
sql/handler.h:
  update function to reflect changes in log tables
  locking logic.
sql/lock.cc:
  Now we allow locking of the log tables for "privileged" threads
  Privileged thread must explicitly close and lock log tables. This
  is required for admin operations such as REPAIR.
sql/log.cc:
  Changes to the file:
  1) Add checks for table schema. It's more important now,
     as we allow rename of the log tables. Since we should
     check for schema when writing to a log table.
     E.g. if one created a table with one-only comlumn and
     renamed it to general_log, the server should cope with
     it.
  2) refactor LOGGER::flush(), so that we can now use the same
     machinery as we use in FLUSH LOGS in other statements:
     whenever we have to perform  a serious operation on the log
     tables, we have to
     (a) lock logger, which blocks other concurrent statements (such 
     as selects) (b) close logs. Then perform an
     exclusive operation, c) reenable logs and d) unlock logger.
  3) Add a function to check if a given table is a log table.
  4) Add support for "privileged" thread
  5) merge is_[general/slow]_log_table_enabled() into one function.
  6) Add new function: reopen _log_tables, which reopens the tables,
     which were enabled (after temporary close, required for admin
     operation)
sql/log.h:
  1) add a new call close_n_lock_tables(). Now we use it instead of
     LOGGER::flush() in FLUSH LOGS implementation.
  2) add a prototype for the function to check if a given
     table is a log table;
  3) add privileged table flag to table logger
  4) merge is_[general/slow]_log_table_enabled()
     into one function.
sql/mysql_priv.h:
  move log table defines to log.h
sql/sql_delete.cc:
  use new function check_if_log_table() instead of direct strcmp
sql/sql_rename.cc:
  Traverse the list of tables in mysql_rename_tables
  to make sure that log tables are processed correctly
  (that is, according to the rules specified in the
  main CS comment)
sql/sql_table.cc:
  1) mysql_admin_table() should disable logs if it performs
     exclusive admin operation on a log table. This way we
     also eliminate warning on REPAIR of the log table.
  2) mysql_create_like_table should read-lock the source table
     instead getting name lock on it. Name lock is too restrictive
     in this case.
sql/share/errmsg.txt:
  Add a new error message for rename of the log tables
sql/table.cc:
  use new function instead of direct strcmp.
  change my_strcasecmp() -> strcmp(), when
  comparing system db and table names
storage/csv/ha_tina.cc:
  update function to reflect changes in log tables
  locking logic.
storage/myisam/ha_myisam.cc:
  update function to reflect changes in log tables
  locking logic.

1 files changed, 83 insertions, 0 deletions

diff --git a/mysql-test/t/log_tables.test b/mysql-test/t/log_tables.test
index 97c83310b4d..f814b258663 100644
--- a/mysql-test/t/log_tables.test
+++ b/mysql-test/t/log_tables.test
@@ -314,6 +314,89 @@ use mysql;
 lock tables general_log read local, help_category read local;
 unlock tables;
 
+#
+# Bug #17544 Cannot do atomic log rotate and
+# Bug #21785 Server crashes after rename of the log table
+#
+
+use mysql;
+# Should result in error
+--error ER_CANT_RENAME_LOG_TABLE
+RENAME TABLE general_log TO renamed_general_log;
+--error ER_CANT_RENAME_LOG_TABLE
+RENAME TABLE slow_log TO renamed_slow_log;
+
+#check rotate logs
+truncate table general_log;
+--replace_column 1 TIMESTAMP 2 USER_HOST 3 THREAD_ID
+select * from general_log;
+
+truncate table slow_log;
+--replace_column 1 TIMESTAMP 2 USER_HOST
+select * from slow_log;
+
+create table general_log_new like general_log;
+rename table general_log TO renamed_general_log, general_log_new TO general_log;
+
+create table slow_log_new like slow_log;
+rename table slow_log TO renamed_slow_log, slow_log_new TO slow_log;
+
+# check that rename checks more then first table in the list
+--error ER_CANT_RENAME_LOG_TABLE
+rename table general_log TO general_log_new, renamed_general_log TO general_log, slow_log to renamed_slow_log;
+
+# now check the content of tables
+--replace_column 1 TIMESTAMP 2 USER_HOST 3 THREAD_ID
+select * from general_log;
+--replace_column 1 TIMESTAMP 2 USER_HOST 3 THREAD_ID
+select * from renamed_general_log;
+
+# the content of the slow log is empty, but we will try a select anyway
+--replace_column 1 TIMESTAMP 2 USER_HOST
+select * from slow_log;
+--replace_column 1 TIMESTAMP 2 USER_HOST
+select * from renamed_slow_log;
+
+# check that we can do whatever we want with disabled log
+set global general_log='OFF';
+RENAME TABLE general_log TO general_log2;
+
+set global slow_query_log='OFF';
+RENAME TABLE slow_log TO slow_log2;
+
+# this should fail
+--error ER_CANT_ACTIVATE_LOG
+set global general_log='ON';
+--error ER_CANT_ACTIVATE_LOG
+set global slow_query_log='ON';
+
+RENAME TABLE general_log2 TO general_log;
+RENAME TABLE slow_log2 TO slow_log;
+
+# this should work
+set global general_log='ON';
+set global slow_query_log='ON';
+# now check flush logs
+flush logs;
+flush logs;
+drop table renamed_general_log, renamed_slow_log;
+use test;
+
+#
+# Bug #21966 Strange warnings on repair of the log tables
+#
+
+use mysql;
+# check that no warning occurs on repair of the log tables
+repair table general_log;
+repair table slow_log;
+# check that no warning occurs on "create like" for the log tables
+create table general_log_new like general_log;
+create table slow_log_new like slow_log;
+show tables like "%log%";
+drop table slow_log_new, general_log_new;
+use test;
+
 # kill all connections
 disconnect con1;
 disconnect con2;