into slow log
While processing a statement, down the mysql_parse execution
stack, the thd->enable_slow_log can be assigned to
opt_log_slow_admin_statements, depending whether one is executing
administrative statements, such as ALTER TABLE, OPTIMIZE,
ANALYZE, etc, or not. This can have an impact on slow logging for
statements that are executed after an administrative statement
execution is completed.
When executing statements directly from the user this is fine
because, the thd->enable_slow_log is reset right at the beginning
of the dispatch_command function, ie, everytime a new statement
is set is set to execute.
On the other hand, for slave SQL thread (sql_thd) the story is a
bit different. When in SBR the sql_thd applies statements by
calling mysql_parse. Right after, it calls log_slow_statement
function to log them if they take too long. Calling mysql_parse
directly is fine, but also means that dispatch_command function
is bypassed. As a consequence, thd->enable_slow_log does not get
a chance to be reset before the next statement to be executed by
the sql_thd. If the statement just executed by the sql_thd was an
administrative statement and logging of admin statements was
disabled, this means that sql_thd->enable_slow_log will be set to
0 (disabled) from that moment on. End result: sql_thd stops
logging slow statements.
We fix this by resetting the value of sql_thd->enable_slow_log to
the value of opt_log_slow_slave_statements right after
log_slow_stement is called by the sql_thd.
To 5.x Release
Notes
=====
This is a backport of BUG#23300 into 5.1 GA.
Original cset revid (in betony):
luis.soares@sun.com-20090929140901-s4kjtl3iiyy4ls2h
Description
===========
When using replication, the slave will not log any slow query
logs queries replicated from the master, even if the
option "--log-slow-slave-statements" is set and these take more
than "log_query_time" to execute.
In order to log slow queries in replicated thread one needs to
set the --log-slow-slave-statements, so that the SQL thread is
initialized with the correct switch. Although setting this flag
correctly configures the slave thread option to log slow queries,
there is an issue with the condition that is used to check
whether to log the slow query or not. When replaying binlog
events the statement contains the SET TIMESTAMP clause which will
force the slow logging condition check to fail. Consequently, the
slow query logging will not take place.
This patch addresses this issue by removing the second condition
from the log_slow_statements as it prevents slow queries to be
binlogged and seems to be deprecated.
