Search Results for: int primary key

Optimizer hints in MySQL 5.7.7 – The missed manual

In version MySQL 5.7.7 Oracle presented a new promising feature: optimizer hints. However it did not publish any documentation about the hints. The only note which I found in the user manual about the hints is: It is now possible to provide hints to the optimizer by including /*+ … */ comments following the SELECT, […]

Illustrating Primary Key models in InnoDB and their impact on disk usage

On a recent engagement I worked with a customer who makes extensive use of UUID() values for their Primary Key and stores it as char(36), and their row count on this example table has grown to over 1 billion rows. The table is INSERT-only (no UPDATEs or DELETEs), and the bulk of their retrieval are PK […]

InnoDB scalability issues due to tables without primary keys

Each day there is probably work done to improve performance of the InnoDB storage engine and remove bottlenecks and scalability issues. Hence there was another one I wanted to highlight: Scalability issues due to tables without primary keys This scalability issue is caused by the usage of tables without primary keys. This issue typically shows […]

How InnoDB promotes UNIQUE constraints

The other day I was running pt-duplicate-key-checker on behalf of a customer and noticed some peculiar recommendations on an InnoDB table with an odd structure (no PRIMARY key, but multiple UNIQUE constraints). This got me thinking about how InnoDB promotes UNIQUE constraints to the role of PRIMARY KEYs. The documentation is pretty clear: [DOCS] When […]

Introduction to Percona XtraBackup 2.1 (MySQL webinar & more)

Percona XtraBackup 2.1 has been in GA now for a little over four months and has some impressive new features to improve backup performance, security, and storage requirements. When used with Percona Server, additional features are enabled that can provide even more dramatic performance improvements. Percona XtraBackup is open source, free MySQL hot backup software […]

The Optimization That (Often) Isn’t: Index Merge Intersection

Prior to version 5.0, MySQL could only use one index per table in a given query without any exceptions; folks that didn’t understand this limitation would often have tables with lots of single-column indexes on columns which commonly appeared in their WHERE clauses, and they’d wonder why the EXPLAIN plan for a given SELECT would […]

Logging Foreign Key errors

In the last blog post I wrote about how to log deadlock errors using Percona Toolkit. Foreign key errors have the same problems. InnoDB only logs the last error in the output of SHOW ENGINE INNODB STATUS, so we need another similar tool in order to have historical data. pt-fk-error-logger This is a tool very […]

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 […]