next-key lock

[geetanjali mehra]

Hello to all,
In repeatable read isolation level, when we issue:

Select * from new where c1 between 12 and 17 for update;

this range will be locked by innodb by using next-key locks.

But, why is is preventing any other session to insert any value beyond that
range; any value above the range and any value below the range. I am unable
to understand this.

Best Regards,
Geetanjali Mehra
Senior Oracle and MySQL DBA Corporate Trainer and Database Security
Specialist

fragmentation in innodb index

[geetanjali mehra]

Hello to all,

I want to know whether my innodb index is fragemented. Is it possible to
know?

Best Regards,
Geetanjali Mehra
Senior Oracle and MySQL DBA Corporate Trainer and Database Security
Specialist

purge thread

[geetanjali mehra]

I want to understand how to tune  innodb_max_purge_lag
http://dev.mysql.com/doc/refman/5.5/en/innodb-parameters.html#sysvar_innodb_max_purge_lag
when history list length is high.


Could anyone explain me.


Best Regards,
Geetanjali Mehra
Senior Oracle and MySQL DBA Corporate Trainer and Database Security
Specialist