MySQL is not a strictly typed database. Given that and the different character types some tricky situation might arise. Especially when it comes to trailing spaces. Since this caused some head scratching hours to a colleague of mine I thought it’s worth a bit more explanation.
To understand the problem first … Continue reading
Recordsize on data volume
This is the first thing you read when it comes to running MySQL on ZFS. InnoDB is using 16k pages so in theory this makes absolute sense. But as in many situation reality beats theory. We had a competing hypothesis about the optimal recordsize so we setup a … Continue reading
Full text is a critical point when it comes to mysql. It used to have that feature in MyISAM but that’s not really maintained anymore nor it is advised to use unless you have a very specific use case in which it might make sense. There are 3rd party solution … Continue reading
Today we had an interesting situation where the same query was executed significantly slower when it was written with GROUP BY instead of DISTINCT and I saw many people still had the assumption that these two types of queries are actually equivalent which is simply not true. Although DISTINCT queries … Continue reading
In MySQL a big portion of the problems you’re facing is different replication delays so there’s no surprise this is one of the most common interview questions on DBA interviews and I still found people having problems with explaining what they would do in a certain situation. This is why … Continue reading
We’re always testing the latest versions of MySQL with most of the environments to make sure that we can find the critical issues before it goes to production. This wasn’t different with the 5.6 MySQL neither. We already started to play with this version in the summer. The first news … Continue reading
(Note: when I’m talking about MySQL I usually assume InnoDB storage engine. Any other case I explicitly tell this is MyISAM or Memory etc.)
I’ve heared an interesting aproach of using Master-slave replication in MySQL.
So the theory was that since updates by primary keys are fast and by … Continue reading
Why is it so important to close connections to databases if there’s no explicit need to keep them open (which usually the case)?
- Icinga reports high usage of allowed connections (>90%) on master MySQL server.
- No running queries or any specific in processlist. All the connections are sleeping … Continue reading
I always hear newer and newer exotic way to store different types of data in MySQL. People are trying to solve the problem of storing complex and not necessary strictly structured data in databases which is fine. But I never understood why to try to be tricky with the simplest … Continue reading
Last week one of my collagues came to me with the following problem. He was not able to create an innodb table. MySQL returned ERROR 1005: Can’t create table (errno: -1). Most of the times this problem is a foreign key related issue but now this wasn’t the case (Foreign key error will return … Continue reading