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Understanding the maximum number of columns in a MySQL table

April 8, 2013 By Stewart Smith 5 Comments

This post was initially going to be two sets of polls: “What is the maximum number of columns in MySQL?” and “What is the minimum maximum number of columns in MySQL?”. Before you read on, ponder those questions and come up with your own answers… and see if you’re right or can prove me wrong! [...]

Filed Under: MySQL Tagged With: columns, CREATE TABLE, ddl, FRM, limits, MySQL, MySQL table, Perl, UNIREG

InnoDB Full-text Search in MySQL 5.6: Part 2, The Queries!

March 4, 2013 By Ernie Souhrada 7 Comments

This is part 2 in a 3 part series. In part 1, we took a quick look at some initial configuration of InnoDB full-text search and discovered a little bit of quirky behavior; here, we are going to run some queries and compare the result sets. Our hope is that the one of two things [...]

Filed Under: Insight for DBAs, Insight for Developers, MySQL Tagged With: Ernie Souhrada, FTS, FullText Search, InnoDB, MyISAM, MySQL 5.6

InnoDB Full-text Search in MySQL 5.6 (part 1)

February 26, 2013 By Ernie Souhrada 1 Comment

I’ve never been a very big fan of MyISAM; I would argue that in most situations, any possible advantages to using MyISAM are far outweighed by the potential disadvantages and the strengths of InnoDB. However, up until MySQL 5.6, MyISAM was the only storage engine with support for full-text search (FTS). And I’ve encountered many [...]

Filed Under: Insight for DBAs, Insight for Developers, MySQL Tagged With: Ernie Souhrada, FTS, FullText Search, InnoDB, MyISAM, MySQL 5.6

Can’t Create Thread: Errno 11 (A Tale of Two Ulimits)

February 4, 2013 By Ernie Souhrada 10 Comments

Recently some of my fellow Perconians and I have noticed a bit of an uptick in customer cases featuring the following error message:

SQLSTATE[HY000] [1135] Can't create a new thread (errno 11); if you are not
out of available memory, you can consult the manual for a possible OS-dependent bug.

1 2	SQLSTATE[HY000] [1135] Can't create a new thread (errno 11); if you are not out of available memory, you can consult the manual for a possible OS-dependent bug.

The canonical solution to this issue, if you do a bit of Googling, is to increase the number of processes / threads available to the MySQL user, typically by adding a [...]

Filed Under: Insight for DBAs, MySQL Tagged With: 90-nproc.conf, Errno 11, Ulimits

Knowing what pt-online-schema-change will do

November 1, 2012 By Daniel Nichter 1 Comment

pt-online-schema-change is simple to use, but internally it is complex. Baron’s webinar about pt-online-schema-change hinted at several of the tool’s complexities. Consequently, users often want to know before making changes what pt-online-schema-change will do when it runs. The tool has two options to help answer this question: –dry-run and –print. When ran with –dry-run and –print, pt-online-schema-change changes nothing [...]

Filed Under: Insight for DBAs, Percona Software Tagged With: pt-online-schema-change

Percona XtraDB Cluster – installation and setup webinar follow up Q&A

October 28, 2012 By Peter Boros 4 Comments

Thanks for all, who attended my webinar, I got many questions and I wanted to take this opportunity to answer them. Q: Even ntp has a delay of 0.3-0.4 between servers does that mean a 0.25 as from logs can be an issue ? A: My demo vms were running for a few hours before [...]

Filed Under: MySQL, XtraDB Cluster

When is MIN(DATE) != MIN(DATE) ?

September 4, 2012 By Ernie Souhrada 5 Comments

Inspiration for this post is courtesy of a friend and former colleague of mine, Greg Youngblood, who pinged me last week with an interesting MySQL puzzle. He was running Percona Server 5.5.21 with a table structure that looks something like this:

CREATE TABLE foo (
 id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
 uid INT UNSIGNED NOT NULL,
 update_time DATETIME NOT NULL,
 ....
 INDEX `uid` (uid, update_time),
 INDEX `bar` (some_other_columns)
 ....
) ENGINE=InnoDB;

CREATE TABLE foo (

id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,

uid INT UNSIGNED NOT NULL,

update_time DATETIME NOT NULL,

....

INDEX `uid` (uid, update_time),

INDEX `bar` (some_other_columns)

....

) ENGINE=InnoDB;

When he ran this query:

SELECT MIN(update_time) FROM foo WHERE update_time IS NOT NULL AND update_time <> '0000-00-00 00:00:00';

1	SELECT MIN(update_time) FROM foo WHERE update_time IS NOT NULL AND update_time <> '0000-00-00 00:00:00';

The result came back as 2012-06-22 10:28:16. [...]

Filed Under: Insight for DBAs, Insight for Developers, MySQL

Percona XtraDB Cluster: Failure Scenarios with only 2 nodes

July 25, 2012 By Frederic Descamps 6 Comments

During the design period of a new cluster, it is always advised to have at least 3 nodes (this is the case with PXC but it’s also the same with PRM). But why and what are the risks ? The goal of having more than 2 nodes, in fact an odd number is recommended in [...]

Filed Under: MySQL, XtraDB Cluster

On Character Sets and Disappearing Tables

June 21, 2012 By Ernie Souhrada 1 Comment

The MySQL manual tells us that regardless of whether or not we use “SET FOREIGN_KEY_CHECKS=0″ before making schema changes, InnoDB will not allow a column referenced by a foreign key constraint to be modified in such a way that the foreign key will reference a column with a mismatched data type. For instance, if we [...]

Filed Under: Insight for DBAs, MySQL

Win Free MySQL Conference Tickets!

March 14, 2012 By Baron Schwartz 3 Comments

We’re giving away three full conference passes (worth $995 each) to the Percona Live MySQL Conference and Expo, and you can win one simply by sharing the conference with your friends and colleagues! Second prize is one of ten copies of the new High Performance MySQL, 3rd Edition (worth $55 each), the recently released update [...]

Filed Under: Events and Announcements, MySQL

Understanding the maximum number of columns in a MySQL table

InnoDB Full-text Search in MySQL 5.6: Part 2, The Queries!

InnoDB Full-text Search in MySQL 5.6 (part 1)

Can’t Create Thread: Errno 11 (A Tale of Two Ulimits)

Knowing what pt-online-schema-change will do

Percona XtraDB Cluster – installation and setup webinar follow up Q&A

When is MIN(DATE) != MIN(DATE) ?

Percona XtraDB Cluster: Failure Scenarios with only 2 nodes

On Character Sets and Disappearing Tables

Win Free MySQL Conference Tickets!

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