Introduction

If your WordPress comment counts got messed up, whether because of a plugin (I'm talking about you, DISQUS) or you messed with your database manually and did something wrong (yup, that's what I just did), fear not – I have a solution for you.

But first, a little background.

Comment Counts In WordPress

Here's how comment counts work in WP:

• Posts live in a table called wp_posts and each has an ID.
• Comments reside in a table called wp_comments, each referring to an ID in wp_posts.
• However, to make queries faster, the comment count is also cached in the wp_posts table, rather than getting calculated on every page load.
  If this count ever gets out of sync with the actual number of comments for some reason, WordPress, while still displaying all comments properly, will simply show the wrong count. …

I will be presenting Galera replication in O'Reilly MySQL Conference & Expo on April 14. Here is the link to the presentation abstract:
Galera - Synchronous Multi-master Replication For InnoDB.
The presentation will be run jointly with Alexey Yurchenko and will focus mostly in the practicalities of managing Galera cluster, like:

• 
  
• Howto download and install MySQL/Galera cluster
  
• Configuration options, clustering use cases and topologies
  
• Managing Galera cluster, joining node(s) in cluster, backups etc...
  
• Application connectivity options
  
• Monitoring Galera cluster, troubleshooting best practices
  

This presentation will …

In Released and new coming features I did not mentioned two additional INFORMATION_SCHEMA tables available in XtraDB:
It is

• INNODB_TABLE_STATS
• INNODB_INDEX_STATS

These table show statistics about InnoDB tables ( taken from InnoDB data dictionary).

INNODB_TABLE_STATS is

• | table_name | table name in InnoDB internal style ('database/table') |
• | rows | estimated number of all rows |
• | clust_size | cluster index (table/primary key) size in number of pages|
• | other_size | other index (non primary key) size in number of pages|
• | modified | internal counter to judge whether statistics recalculation should be done |

INNODB_INDEX_STATS is

• | table_name | table name in …

Finally, it is available for orders: The MySQL Admin Cookbook is the first book I have written and it is now ready for shipping. You can find more information about it at the publisher's website, including a free sample chapter!

I have yet to receive my sample copy, however that should not keep you from going ahead early and ordering it, e. g. from amazon.de. For your convenience, here is a direct link:

On Amazon you can also have a look at the index and a few pages of the first chapter.

More international points of sale can be found on the publisher's website, …

Yes, it's been a while. I did not blog for quite a long time. In April, I posted an article on MySQL on Solaris, and with that article I meant to go back to my regular blogging, i.e. writing an article every week or so. Soon after that article, I took responsibility of the European Presales team for Sun Software, Application Server Platform to be precise. APS included MySQL, the Identity Management software, SOA products, Glassfish and Java. This job was very similar to what I used to do between 1998 and 2002 and I was really excited to work with a large team again.
Now that we are part of Oracle, I am back to my original role MySQL, in the European Presales team, now called Sales Consulting.
It's really nice to be back. I really missed the excitement and the hands on that characterises the MySQL business. APS was a fantastic place to work and the incredibly talented people I've met are genuinely one of the best team I have ever worked …

So you're running the benchmark/stress test - how do you tell if MySQL server is really loaded ? This looks like the trivial question but in fact, especially when workload consists of simple queries I see the load generation and network really putting a lot less load on MySQL than expected. For example you may have 32 threads (or processes) running queries as fast as they can... does it really mean there is an 32 concurrent queries ran all the time ? It may be the case or it may be not...

Take a look at this server for example:

PLAIN TEXT CODE:

1. [root@db01 ~]# mysqladmin -i1  extended | grep Threads_running
2. | Threads_running                       | 1                    |
3. | Threads_running        …

The main reason for that VFP to MYSQL conversion project was that the customer is in the process of growth and is establishing multiple locations which all will use the same system to some extend. In addition to that we are going from a system where everyone on the system did pretty much everything to one where there are only going to be a few people who have access to everything and most will just work in their “special corner” of the system. Some will just do order entry, some receivables, some sales personel will have only access to their clients etc etc.

At present the VFP system resides on a shared Network drive and if a modification is needed well then one just replaces or adds a Screen or report on that particular shared network drive. Now it would be necessary to push this to multiple locations, in different configurations and that shared network drive wont do anymore – especially over the internet.

Luckely all …

Hello folks, it’s great to be back from hiatus. This is the 183rd edition of Log Buffer (arguably the best edition of Log Buffer yet!), the weekly review of database blogs.

The last time I wrote this was just under 2 years ago!!! WoW. Things have changed. Sun bought MySQL, Oracle bought Sun. Those were bombshell deals. At least you can rest assured that some things can be constant. I still eat my daily serving of broccoli (among other healthful “things”). I urge you all to go the fridge and grab some veggies prior to sitting down for this week’s… ahem… digest.

Starting with Oracle, Pythian’s own Alex Fatkulin illustrates a bug (?…likely) that could lead to logically corrupted data. …

I started with my VFP to MYSQL conversion in earnest at the end of December. To keep the cost down until I know what I am doing I am using the GA version 5.1.43 and now WORKBENCH to do my development. Actually initially I used the 5.0 Administrator and Query which worked fine but did not have any supports for triggers. Workbench 5.1.18 frustrated me for many reasons so I started to use the Beta of 5.2 which in my opinion is better but still a Beta. Trying to help to improve I filed about 20 or so bug reports and got into email conversations with the developers.

In course of that I mentioned the process of converting from VFP (Visual Foxpro) to MYSQL and I was asked to Blog about my experiences with that and feed it to Planet MySQL. Starting to read Planet MySQL I must say that I am probably an oddity here as there does not seem to be any VFP people here. For that reason I also fed and anounced my Blog to some VFP boards and feeds. I even got …

PBXT continues to amaze me. I want to know that maximum rate at which an engine can perform IO. I ran sysbench on MySQL 5.1.45 on a server with fast IO for PBXT, InnoDB (1.0.6 plugin) and MyISAM.

The test used sysbench readonly configured to fetch rows by primary key using the HANDLER statement. This option is available in sysbench on Launchpad. The test used a uniform distribution and the engines were configured to cache about 10% of the table. Most row fetches should require 1 disk read. In this case, the disk is very fast as tmpfs was used to store database files. We can get 10,000 to 100,000 IOPs at a commodity price. Can MySQL benefit from this? Yes it can, but this varies greatly between storage engines.

The peak QPS for PBXT is 2X better than InnoDB (1.0.6 plugin). The peak QPS for MyISAM is 2X better than PBXT. A graph of the results is …