pt-table-checksum changes binlog_format even if already set to statement

[Rob Smith]

pt-table-checksum currently changes the session binlog_format to statement no matter what it currently is set to. This requires the super privilege on mysql 5.1.29+.

From http://dev.mysql.com/doc/refman/5.1/en/replication-options-binary-log.html#sysvar_binlog_format

You must have the SUPER privilege to set the global binlog_format value. Starting with MySQL 5.1.29, you must have the SUPER privilege to set either the global or session binlog_format value. (Bug #39106)

pt-table-checksum should check to see the current value of binlog_format before attempting to change it.

[Sheeri K. Cabral (awfief)]

This is a security issue - there shouldn't be a need for a SUPER user for this functionality. Especially since many folks will store the password for the checksum user in a script somewhere.

[Baron Schwartz (baron-xaprb)]

Brian,

I looked at the branch changes. It can be a bit cleaner code. Old:

      my $sql = 'SHOW VARIABLES LIKE "binlog_format"';
      my (undef, $original_binlog_format) = $dbh->selectrow_array($sql);

Suggested:

      my $sql = 'SELECT @@binlog_format';
      my ($original_binlog_format) = $dbh->selectrow_array($sql);

Why this matters:

1. Less confusing code in the Perl
2. Doesn't use a double-quoted string in the SQL, which we know we're going to have to avoid someday to make the tools behave when SQL_MODE=ANSI

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PT-454