For some time now I've been working on a Drupal site that consists mainly of scraped content from a proprietary, ASP based CMS from the late nineties. The Simple HTML Dom Parser, used from within a drush script, has been invaluable. It made scraping the old site content and importing it as Drupal nodes a relative breeze. (No access to the database used by the CMS, boo!)

Part of setting up the new site is importing users and their content profile nodes from a different Drupal site, that was setup a year or two ago to manage an event.

I had hoped there would be a way for me to export these users and their profile nodes from one Drupal to the other, but though I found modules to export one or the other, I might still end up with profile nodes that were no longer related to their users. Of course, that's pretty useless.

When I remembered I was also supposed …

For some time now I've been working on a Drupal site that consists mainly of scraped content from a proprietary, ASP based CMS from the late nineties. The Simple HTML Dom Parser, used from within a drush script, has been invaluable. It made scraping the old site content and importing it as Drupal nodes a relative breeze. (No access to the database used by the CMS, boo!)

Part of setting up the new site is importing users and their content profile nodes from a different Drupal site, that was setup a year or two ago to manage an event.

I had hoped there would be a way for me to export these users and their profile nodes from one Drupal to the other, but though I found modules to export one or the other, I might still end up with profile nodes that were no longer related to their users. Of course, that's pretty useless.

When I remembered I was also supposed …

HandlerSocket is cool. But, it turns out there are a few issues.

Justin Swanhart points out HandlerSocket currently lacks atomic operations . Since HandlerSocket uses different connections for reading and writing, you can’t increment/decrement a value without creating a race condition.

Still, the idea of skipping SQL interpretation and just reading the data you know you want is a great one.  Writing data might even be better. But being able to use both SQL and NoSQL could be really wonderful.  What if we could use complex queries to update complex tables and pluck values out as needed.  For example, queries to analyze current weather conditions and produce forecasts that we could then retrieve via a location key? What about updating current condition data …

The HandlerSocket plugin for MySQL currently lacks atomic operations .  It is impossible to implement counters (increment/decrement value) or REPLACE functionality with the current implementation. 

It currently exceeds the performance of Memcache for get/set operations, but I want to see how fast it is once atomic operations are implemented. Until then, I don't think it is a serious contender for replacing Memcache for the cache layer in a complex environment.

The HandlerSocket plugin for MySQL currently lacks atomic operations .  It is impossible to implement counters (increment/decrement value) or REPLACE functionality with the current implementation. 

It currently exceeds the performance of Memcache for get/set operations, but I want to see how fast it is once atomic operations are implemented. Until then, I don't think it is a serious contender for replacing Memcache for the cache layer in a complex environment.

How well do you understand InnoDB locking? The documentation is good but would benefit from a few examples. If you want to debug contention for InnoDB then you need to understand record, gap and next-key locks, the reasons for using next-key locks and the locks used by different statements.

This is an example of contention between concurrent transactions that modify different rows. The second transaction blocks on the first when repeatable-read cursor isolation is used. The second transaction does not block on the first when read-committed is used.

The problem occurs because the delete statement gets a next-key …

This document was updated and tested for CentOS 6.0

In my last two posts I installed the HandlerSocket plugin into MariaDB and showed how to use it with Perl.  That’s good, but if you are thinking of using HandlerSocket  I’m guessing you have a very high traffic website and it’s written in PHP.  In this post I’m going to connect HandlerSocket with PHP.  In the next post I’ll discuss using HandlerSocket on a production system.

There are a couple of HandlerSocket php modules projects.  I tried each of them and I found PHP-HandlerSocket was the best.  Both of them are still rough and neither of them have documentation beyond their source code.  Maybe this will move things forward.

Here are the applications you need to have installed that where not installed in my last two posts.  Run this to …

Following the excellent post of Yoshinori about exceeding 750 000 qps with handler_socket,  i was curious to make my own opinion on the state of MySQL and MariaDB regarding simple primary key search.

Quoting  "Most of high scale web applications use MySQL + memcached. Many of them use also NoSQL like TokyoCabinet/Tyrant. In some cases people have dropped MySQL and have shifted to NoSQL. One of the biggest reasons for such a movement is that it is said that NoSQL performs better than MySQL for simple access patterns such as primary key lookups. Most of queries from web applications are simple so this seems like a reasonable decision"

I’m a big fan of NoSQL when it comes to remove useless work put on some …

I pushed more changes to the Facebook patch and merged up to MySQL 5.1.52. Hopefully I will begin pushing patches for MySQL 5.5 soon. The changes include:

• Preserve symlinks for InnoDB datafiles during DDL statements
• Add index_statistics to the information_schema
• Set counters in the user_statistics table. This required several changes: one, two, …

There are some very well-known differences between Innodb and MyISAM e.g. Innodb supports transactions, MyISAM does not etc. However, I am goint to list some not-so-well-known differences here for the reader. Please feel free to suggest more through comments below.