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 [...]
Helgrinding MySQL with InnoDB for Synchronisation Errors, Fun and Profit
November 24, 2011 By 2 Comments
It is no secret that bugs related to multithreading–deadlocks, data races, starvations etc–have a big impact on application’s stability and are at the same time hard to find due to their nondeterministic nature. Any tool that makes finding such bugs easier, preferably before anybody is aware of their existence, is very welcome.
How to replace a NDB node on EC2
June 9, 2011 By 10 Comments
NDB cluster is a very interesting solution in term of high availability since there are no single point of failure. In an environment like EC2, where a node can disappear almost without notice, one would think that it is a good fit. It is indeed a good fit but reality is a bit trickier. The [...]
ACTIVE with Locks – Now thats a problem !
June 2, 2011 By 2 Comments
One of item I always look at SHOW ENGINE INNODB STATUS to see if there are any transactions spending very long time in ACTIVE state. In the perfect world if you’re running online system you should not see transactions spending more than couple of seconds in ACTIVE state. Especially ACTIVE transactions which do not currently [...]
MySQL Connection Timeouts
April 19, 2011 By 4 Comments
Sometimes on very busy MySQL server you will see sporadic connection timeouts, such as Can’t connect to MySQL server on ‘mydb’ (110). If you have connects timed in your application you will see some successful connections taking well over the second. The problem may start very slow and be almost invisible for long time, for [...]
How to use tcpdump on very busy hosts
April 18, 2011 By 17 Comments
Often I run into problems when trying to use mk-query-digest with tcpdump on “very” busy hosts. You might be thinking, “very busy is a relative and unquantifiable term,” and you’d be right, so I’ll phrase this differently. Let me give a little background to the problem first. Mk-query-digest tries to handle dropped or missing packets [...]
Using Flexviews – part two, change data capture
March 25, 2011 By 26 Comments
In my previous post I introduced materialized view concepts. This post begins with an introduction to change data capture technology and describes some of the ways in which it can be leveraged for your benefit. This is followed by a description of FlexCDC, the change data capture tool included with Flexviews. It continues with an [...]
How Percona strives to remain neutral and independent
March 21, 2011 By Leave a Comment
Many of the prominent companies in the MySQL ecosystem are Percona customers, including hardware manufacturers, software developers, hosted service providers, and appliance developers. We perform paid and unpaid research on their products, and we publish blog posts related to their products or services. Independence and objectivity are core Percona values. How do we balance the [...]
How Percona diagnoses MySQL server stalls
March 3, 2011 By 6 Comments
We receive many requests for help with server stalls. They come under various names: lockup, freeze, sudden slowdown. When something happens only once or twice a day, it can be difficult to catch it in action. Unfortunately, this often leads to trial-and-error approaches, which can drag on for days (or even months), and cause a [...]
Sharing an auto_increment value across multiple MySQL tables
October 4, 2010 By 9 Comments
The title is SEO bait – you can’t do it. We’ve seen a few recurring patterns trying to achieve similar – and I thought I would share with you my favorite two: Option #1: Use a table to insert into, and grab the insert_id:
1 2 3 4 5 | CREATE TABLE option1 (id int not null primary key auto_increment) engine=innodb; # each insert does one operations to get the value: INSERT INTO option1 VALUES (NULL); # $connection->insert_id(); |
Option #2: Use a table with one just row:
1 2 3 4 5 6 | CREATE TABLE option2 (id int not null primary key) engine=innodb; INSERT INTO option2 VALUES (1); # start from 1 # each insert does two operations to get the value: UPDATE option2 SET id=@id:=id+1; SELECT @id; |
