Search Results for: what does -time mean

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

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:

When he ran this query:

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

dbqp and Xtrabackup testing

So I’m back from the Percona dev team’s recent meeting.  While there, we spent a fair bit of time discussing Xtrabackup development.  One of our challenges is that as we add richer features to the tool, we need equivalent testing capabilities.  However, it seems a constant in the MySQL world that available QA tools often […]

Preprocessing Data

There are many ways of improving response times for users. There are some people that spend a lot of time, energy and money on trying to have the application respond as fast as possible at the time when the users made the request. Those people may miss out on an opportunity to do some or […]

What is innodb_support_xa?

A common misunderstanding about innodb_support_xa is that it enables user-initiated XA transactions, that is, transactions that are prepared and then committed on multiple systems, with an external transaction coordinator. This is actually not precisely what this option is for. It enables two-phase commit in InnoDB (prepare, then commit). This is necessary not only for user-initiated […]

Sample datasets for benchmarking and testing

Sometimes you just need some data to test and stress things. But randomly generated data is awful — it doesn’t have realistic distributions, and it isn’t easy to understand whether your results are meaningful and correct. Real or quasi-real data is best. Whether you’re looking for a couple of megabytes or many terabytes, the following […]

Tuning InnoDB Concurrency Tickets

InnoDB has an oft-unused parameter innodb_concurrency_tickets that seems widely misunderstood. From the docs: “The number of threads that can enter InnoDB concurrently is determined by the innodb_thread_concurrency variable. A thread is placed in a queue when it tries to enter InnoDB if the number of threads has already reached the concurrency limit. When a thread […]