As an instructor with Percona I’m sometimes asked about the differences between the READ COMMITTED and REPEATABLE READ transaction isolation levels. There are a few differences between READ-COMMITTED and REPEATABLE-READ, and they are all related to locking.
Differences between READ-COMMITTED and REPEATABLE-READ transaction isolation levels
August 28, 2012 By 3 Comments
Full Text Search Webinar Questions Followup
August 24, 2012 By 5 Comments
I presented a webinar this week to give an overview of several Full Text Search solutions and compare their performance. Even if you missed the webinar, you can register for it, and you’ll be emailed a link to the recording. During my webinar, a number of attendees asked some good questions. Here are their questions and my [...]
Percona XtraDB Cluster: Multi-node writing and Unexpected deadlocks
August 17, 2012 By 17 Comments
Percona XtraDB Cluster (PXC) and the technology it uses (Galera) is an exciting alternative to traditional MySQL replication. For those who don’t know, it gives you: Fully Synchronous replication with a write latency increase equivalent to a ping RTT to the furthest node Automatic cluster synchronization, both incremental and full restores The ability to read [...]
Innodb Table Locks
July 31, 2012 By 4 Comments
Innodb uses row level locks right ? So if you see locked tables reported in SHOW ENGINE INNODB STATUS you might be confused and rightfully so as Innodb table locking is a bit more complicated than traditional MyISAM table locks. Let me start with some examples. First lets run SELECT Query:
1 2 3 4 5 | ---TRANSACTION 12303, ACTIVE 26 sec mysql tables in use 2, locked 0 MySQL thread id 53038, OS thread handle 0x7ff759b22700, query id 3918786 localhost root Sending data select count(*) from sbtest,sbtest x Trx read view will not see trx with id >= 12304, sees < 12301 |
As you can [...]
Find and remove duplicate indexes
June 20, 2012 By 9 Comments
Having duplicate keys in our schemas can hurt the performance of our database: They make the optimizer phase slower because MySQL needs to examine more query plans. The storage engine needs to maintain, calculate and update more index statistics DML and even read queries can be slower because MySQL needs update fetch more data to [...]
Win Free MySQL Conference Tickets!
March 14, 2012 By 3 Comments
We’re giving away three full conference passes (worth $995 each) to the Percona Live MySQL Conference and Expo, and you can win one simply by sharing the conference with your friends and colleagues! Second prize is one of ten copies of the new High Performance MySQL, 3rd Edition (worth $55 each), the recently released update [...]
The relationship between Innodb Log checkpointing and dirty Buffer pool pages
February 17, 2012 By 10 Comments
This is a time-honored topic, and there’s no shortage of articles on the topic on this blog. I wanted to write a post trying to condense and clarify those posts, as it has taken me a while to really understand this relationship. Some basic facts Most of us know that writing into Innodb updates buffer [...]
Avoiding auto-increment holes on InnoDB with INSERT IGNORE
November 29, 2011 By 8 Comments
Are you using InnoDB tables on MySQL version 5.1.22 or newer? If so, you probably have gaps in your auto-increment columns. A simple INSERT IGNORE query creates gaps for every ignored insert, but this is undocumented behaviour. This documentation bug is already submitted. Firstly, we will start with a simple question. Why do we have [...]
Emulating global transaction ID with pt-heartbeat
November 4, 2011 By 6 Comments
Global transaction IDs are being considered for a future version of MySQL. A global transaction ID lets you determine a server’s replication position reliably, among other benefits. This is great when you need to switch a replica to another master, or any number of other needs. Sometimes you can’t wait for the real thing, but [...]
Updated Percona Server and Percona XtraBackup documentation
October 3, 2011 By Leave a Comment
We’ve just gone live with a new way of publishing and maintaining documentation for Percona Server and Percona XtraBackup. We are now using Sphinx to generate the documentation that we publish on the web site. Sphinx was originally created for the new Python documentation, and has won us over due to the simple markup, ease of [...]
