Search Results for: mysql index timestamp column

Percona Toolkit 2.1.9 is ready

About a month ago, we held a bug raffle for Percona Toolkit 2.1.9.  The turnout was good and the resulting release is worth upgrading to, especially if you were affected by the backwards-incompatible changes to pt-heartbeat in 2.1.8.  Here are the release notes for Percona Toolkit 2.1.9 which highlight the bugs fixed: Percona Toolkit 2.1.9 has been released. […]

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 […]

Timezone and pt-table-checksum

I recently worked through an issue with a client trying to detect data drift across some servers that were located in different timezones.  Unfortunately, several of the tables had timestamp fields and were set to a default value of CURRENT_TIMESTAMP.  From the manual, here is how MySQL handles timezone locality with timestamp fields: Values for TIMESTAMP columns are […]

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. […]

When EXPLAIN estimates can go wrong!

I have been working with a few customer cases and one interesting case popped up. The customer was facing a peculiar problem where the rows column in the EXPLAIN output of the query was totally off. The actual number of rows was 18 times more than the number of rows reported by MySQL in the […]

Joining on range? Wrong!

The problem I am going to describe is likely to be around since the very beginning of MySQL, however unless you carefully analyse and profile your queries, it might easily go unnoticed. I used it as one of the examples in our talk given at phpDay.it conference last week to demonstrate some pitfalls one may […]

To UUID or not to UUID ?

Brian recently posted an article comparing UUID and auto_increment primary keys, basically advertising to use UUID instead of primary keys. I wanted to clarify this a bit as I’ve seen it being problems in so many cases. First lets look at the benchmark – we do not have full schema specified in the article itself […]

My Innodb Feature wishes

At Users Conference Heikki did good presentation about Innodb planned features. I did not see some of big and tiny wishes listed so I was making notes. Here is what I’d like to see Packed indexes. In many cases then difference in Performace with MyISAM and Innodb is huge for read only workload it is […]