November 22, 2014

Idea: Couple of more string types

MySQL has a lot of string data types – CHAR, VARCHAR, BLOB, TEXT, ENUM and bunch of variants such as VARBINARY but I think it is not enough I would also like to see type HEXCHAR which would be able to store hex strings, such as those returned as MD5() and SHA1() efficiently. With little […]

How to obtain the “LES” (Last Executed Statement) from an Optimized Core Dump?

Ever ran into a situation where you saw “some important variable you really needed to know about=<optimized out>” while debugging?

SQL Injection Questions Followup

I presented a webinar today about SQL Injection, to try to clear up some of the misconceptions that many other blogs and articles have about this security risk.  You can register for the webinar even now that I’ve presented it, and you’ll be emailed a link to the recording, which will be available soon. During […]

How to deal with MySQL deadlocks

A deadlock in MySQL happens when two or more transactions mutually hold and request for locks, creating a cycle of dependencies. In a transaction system, deadlocks are a fact of life and not completely avoidable. InnoDB automatically detects transaction deadlocks, rollbacks a transaction immediately and returns an error. It uses a metric to pick the […]

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 […]

MySQL compression: Compressed and Uncompressed data size

MySQL has information_schema.tables that contain information such as “data_length” or “avg_row_length.” Documentation on this table however is quite poor, making an assumption that those fields are self explanatory – they are not when it comes to tables that employ compression. And this is where inconsistency is born. Lets take a look at the same table […]

Generating test data from the mysql> prompt

There are a lot of tools that generate test data.  Many of them have complex XML scripts or GUI interfaces that let you identify characteristics about the data. For testing query performance and many other applications, however, a simple quick and dirty data generator which can be constructed at the MySQL command line is useful. […]

Reducer.sh – A powerful MySQL test-case simplification/reducer tool

Let me start by saying a big “thank you” to the staff at Oracle for deciding to open source reducer.sh. It’s a tool I developed whilst I was working for them several years ago. Its sole purpose is to do one thing – but do it good: test-case simplification. So, let’s say some customer just […]

Using sysbench 0.5 for performing MySQL benchmarks

Given the recent excitement & interest around OpenStack I wanted to make sure I was ready to conduct appropriate evaluations of system performance.  I generally turn to sysbench since it comes with a variety of different tests (accessed via –test= option interface), including: fileio – File I/O test cpu – CPU performance test memory – […]

Percona XtraDB Cluster 5.6.20-25.7 is now available

Percona is glad to announce the new release of Percona XtraDB Cluster 5.6 on September 1st 2014. Binaries are available from downloads area or from our software repositories. Based on Percona Server 5.6.20-68.0 including all the bug fixes in it, Galera Replicator 3.7, and on Codership wsrep API 25.7, Percona XtraDB Cluster 5.6.20-25.7 is now […]