October 22, 2014

How to avoid hash collisions when using MySQL’s CRC32 function

Percona Toolkit’s  pt-table-checksum performs an online replication consistency check by executing checksum queries on the master, which produces different results on replicas that are inconsistent with the master – and the tool pt-table-sync synchronizes data efficiently between MySQL tables. The tools by default use the CRC32. Other good choices include MD5 and SHA1. If you have installed the FNV_64 user-defined function, pt-table-sync will […]

Exploring message brokers

Message brokers are not regularly covered here but are, nonetheless, important web-related technologies. Some time ago, I was asked by one of our customer to review a selection of OSS message brokers and propose a couple of good candidates. The requirements were fairly simple: behave well when there’s a large backlog of messages, be able […]

InnoDB file formats: Here is one pitfall to avoid

UPDATED: explaining the role of innodb_strict_mode and correcting introduction of innodb_file_format Compressed tables is an example of an InnoDB feature that became available with the Barracuda file format, introduced in the InnoDB plugin. They can bring significant gains in raw performance and scalability: given the data is stored in a compressed format the amount of […]

Crash-resistant replication: How to avoid MySQL replication errors

Percona Server’s “crash-resistant replication” feature is useful in versions 5.1 through 5.5. However, in Percona Server 5.6 it’s replaced with Oracle MySQL 5.6’s “crash safe replication” feature, which has it’s own implementation (you can read more about it here). A MySQL slave normally stores its position in files master.info and relay-log.info which are updated by […]

More on MySQL Error Messages

I wrote about MySQL Error Messages before and as you might guess I’m not very happy with quality for error messages it produces. Now I’m revisiting this subject with couple of more annoying examples I ran into during last couple of days.

Missleading Innodb message on recovery

As I wrote about 2 years ago the feature of Innodb to store copy of master’s position in Slave’s Innodb tablespace got broken. There is a lot of discussions at the corresponding bug report while outcome of the fix remained uncertain for me (the bug is market duplicate while the bugs it seems to be […]

MySQL Error Message Nonsenses

What MySQL honestly was never good at is giving good helpful error messages. Start with basics for example – The error message in case of syntax error gives you information about tokens near by but little details:

It would be much better if MySQL would give error give exact position of error (with complex […]

MySQL VIEW as performance troublemaker

I start to see applications being built utilizing VIEWs functionality which appeared in MySQL 5.0 and quite frequently VIEWs are used to help in writing the queries – to keep queries simple without really thinking how it affects server performance. Even worse than that – looking at the short table which just gets single row […]

Test Drive of Solid

Not so long ago Solid released solidDB for MySQL Beta 3 so I decided now is time to take a bit closer look on new transactional engine for MySQL. While my far goal is the performance and scalability testing before I wanted to look at basic transactional properties such as deadlock detection, select for update […]

How reliable RAID really is

This post is not exactly about MySQL Performance or about Performance at all, but I guess it should be interested to many MySQL DBAs and other people involved running MySQL In production. Recently I’ve been involved in troubleshooting Dell Poweredge 2850 system running RAID5 using 6GB internal hard drives, which give about 1.4TB of usable […]