As MySQL Manual Says Query Cache works with transactions with Innodb tables but it does not tell you how and with which restrictions.

According to my tests it works but it is very restricted and one could expect it to work much better:

The result set can be retrieved from query cache (for statements both inside and outside of transactions) until there is a statement inside transactions which modifies the table. As soon as table is modified in transaction it becomes uncachable by query cache until that transaction is committed. Not only query cache can't be used inside the same transaction which modified data but also in other concurrent transactions which do not even see the changes done yet

Of course such implementation is rather restricted. Queries outside of transactions well could use query cache until it is invalidated by …

So my challenge last week was to convert almost a billion records in 37 databases and 74 tables. Oh, and I wanted to do it only during the night (between 12:30AM and 6AM) and in the least number of nights.

This was not my first massive MyISAM to InnoDB migration, nonetheless, I still manged to learn a few things. We're at a stage where MyISAM just isn't the solution any more. Our plans are to go almost 100% InnoDB and this migration project completes yet another massive step towards that direction.

The first night was depressing. I applied every trick up my sleeve but only ended up getting 9.48% complete. Second night was only half depressing allowing me to complete ~ 33%. Third night was a charm and I got ~42.5% done. I would have finished the project that night but there was some storage issue …

Obviously, 2008 is off to a roaring start for open soure M&A. Amid all of the deals and our usual discussions with open source software vendors, we’re hearing more and more executives talk about the long-term potential of business based on open code. The SpringSource acquisition of Covalent is a perfect example. We had just written about how Covalent was an attractive M&A target, and even though we may have viewed the acquirer, SpringSource, as more of a fellow target, the deal illustrates an interesting approach to the open source opportunity.

Both Covalent CEO Mark Brewer, who with other company executives bought out Covalent’s original investors, and SpringSource CEO Rod Johnson said their deal was not an effort to get dressed up for acquisition. While the combined company will remain an attractive acquisition target to SIs, OS vendors and others …

MySQL 5.0.51a was released today, which is a security hotfix release without any new features compared with 5.0.51. It fixes CVE-2007-6303, CVE-2007-6304, CVE-2008-0226 and CVE-2008-0227. These problems are already fixed in Debian with 5.0.32-7etch4 and …

Jason Hull of OpenSource Connections, a company in my town, posted an article on what Sun's acquisition of MySQL means for the US government. I thought Planet MySQL readers might appreciate a different angle on the issue than many of the Planet MySQL posts, which are often focused on business or community more than government. (I'm just passing the link along, not agreeing or disagreeing).

American LaFrance has filed for Chapter 11 after not being able to properly migrate from their ex-parent company's ERP system to a new one that was being implemented by IBM. They said that the new system caused production disruptions and left the company with a $100m debt. The company is now taking action "based upon services provided by IBM in connection with the problem-riddled transition to the ERP system."

Hmmm... since the transition was done last year, I wonder whether IBM really is to blame? Did they not have a QA environment?

A useful SQL query I worked out yesterday.

It finds all the indexes in the database "my_database" that have a cardinality/count ratio of less than 0.1%

Such indexes are probably not very useful, and should be looked at carefully to justify their existence.


use information_schema;

select tables.table_name, statistics.index_name, statistics.cardinality, tables.table_rows

  from tables

  join statistics

  on (statistics.table_name = tables.table_name

   and statistics.table_schema = 'my_database'

   and ((tables.table_rows / statistics.cardinality) > 1000));



I worked this out on my current MySQL PS gig. The client has indexes on nearly every column of nearly every table. For example, all of their customers are in Texas, but they …

And on goes my fascination with open source companies and their valuations…

I was reading Stephen O’Grady’s commentary on open source companies and their valuations prompted by the recent acquisition of MySQL by Sun for $1 billion. He quotes Jeff Gould who logically questions whether Sun can make the acquisition pay-off.

Stephen also quotes a piece from Knowledge@Wharton on the myth of market share.

It is a common practice of many companies to focus their attention on grabbing market share from their competitors. But such efforts can actually be detrimental to the firm’s profitability, according to Wharton marketing professor J. Scott …

The purpose of this post isn't by any way to bad mouth MySQL but rather to show the impact of lack of qualified DBAs to those who use MySQL.

I was shocked last year, when a CTO of a large company confided in me and said basically that they are so tired of searching for qualified MySQL DBAs that they may switch to Oracle. At some point, I guess the frustration alone can justify an otherwise unneeded cap-ex of such magnitude.

Today, I hear that ValueCentric, a pharmaceutical technology consulting firm based in New York, has decided to let go of MySQL in their environment and instead switched to Oracle on Oracle Linux.
"as the firm expanded and began taking on bigger clients like AstraZeneca, Roche and P&G Pharmaceuticals, company officials …

The rate of open source M&A continues apace, this time involving two open source software vendors. SpringSource has announced plans to acquire Covalent Technologies for an undisclosed fee. At first glance the deal makes a lot of sense as it marries SpringSource’s Spring Framework-related products and services with the Apache support and services offered by Covalent.

Coincidentally, as news of the deal filtered through to me I happened to be on the phone with …