[TYPO3-english] Saving pages in BE locks complete database - working workaround

[Christopher Lörken]

As a follow-up for this problem: Thanks to some comments on 
http://bugs.mysql.com/bug.php?id=39091 I've been able to work around the 
problem.

The reason for the database locks was due to a bug in MySQL which takes 
extremely long to clear it's query cache when it is large and a lot of 
entries in it are invalidated.

We had a query cache size of 3GB and reducing it to 256MB effectively 
got rid of the problem for us.


As I wrote the problem arose when updating the "pages" table since in a 
Typo3 installation very many queries are issued on that table and hence 
stored in the query cache. One of the things which makes it probably 
even worse is the fact that the standard select queries on that table 
have timestamps of the current time in seconds in them so that they are, 
even for the same user, new every second which effectively floods the 
query cache with useless queries. And in a setup with lots of RAM 
available and a large query cache, this will cause the problem.


Anyway, thanks for your feedback. Maybe this note will help others.

Regards,
Christopher