Search Results for: mysql foreign key innodb

InnoDB’s gap locks

One of the most important features of InnoDB is the row level locking. This feature provides better concurrency under heavy write load but needs additional precautions to avoid phantom reads and to get a consistent Statement based replication. To accomplish that, row level locking databases also acquire gap locks. What is a Phantom Read A […]

Best kept MySQLDump Secret

Many people use mysqldump –single-transaction to get consistent backup for their Innodb tables without making database read only. In most cases it works, but did you know there are some cases when you can get table entirely missing from the backup if you use this technique ? The problem comes from the fact how MySQL’s […]

Hijacking Innodb Foreign Keys

I guess I’m first to post in 2012 so Happy New Year all blog readers ! Now back to HardCore MySQL business – foreign Keys. MySQL supported Foreign Keys for Innodb for many years, yet rudimentary support initially added in MySQL 3.23.44 have not been improved in new releases as much as I’d like. We […]

Beware the Innodb Table Monitor

As I stated in my last post, I decided to use the Innodb Table monitor to diagnose an Index count mismatch error a customers found in their mysqld.err log to verify if the problem still existed. The Innodb Table Monitor has existed for basically forever in Innodb (the MySQL manual discusses it back in the 4.1 […]

Eventual Consistency in MySQL

We’re told that foreign key constraints are the best way to enforce logical referential integrity (RI) in SQL, preventing rows from becoming orphaned.  But then we learn that the enforcement of foreign keys incurs a significant performance overhead.1,2 MySQL allows us to set FOREIGN_KEY_CHECKS=0 to disable enforcement of RI when the overhead is too high.  But […]

Improved InnoDB fast index creation

One of the serious limitations in the fast index creation feature introduced in the InnoDB plugin is that it only works when indexes are explicitly created using ALTER TABLE or CREATE INDEX. Peter has already blogged about it before, here I’ll just briefly reiterate other cases that might benefit from that feature: when ALTER TABLE […]