I'm reading this fantastic book but I'm having some problems with the chapter 5, "memcache and MySQL".

I think the approach described in this chapter is very usefull especially when you're creating complex application with a huge amount of memcache keys; in an consistent application you want that cached objects referencing to older information previously saved in a MySQL table have to be immediately deleted from the memcache, preserving the overall data coherence.
This task could be easly done with a simple trigger in MySQL where, each time you remove a row from a table automatically the trigger send a memc_delete() call to the memcache server, specify the key of the cached element to remove.

Right now the only problems seems to be the MySQL plugin described in this chapter; infact the memcached-udfs project is out of maintenance and is not possible to compile this plugin in an updated enviroment with the last libmemcached (I'm using the 0.40 but the same problems seems to be affected in older version).
It seems like the source point to deprecated functions/variables name and also fixing that from the source code, when you try to import and install the memcached-udfs functions in the MySQL server some pointing errors are displayed, making impossible the use of this library.

In the project page there are a lots of bug reported but right now nobody try to fix those and make this library updated.

I think this is a big issue especially in a new book released just a couple of months ago.

Hi there - thanks for letting me know about that. I need to get out a new release of the UDFs.

Also, another way to make sure you delete items accordingly is to use expiry times for items that you want refreshed more often, or whenever you perform any write action (insert, delete, update), make sure to do the same with memcached.