[support] how cache works: on the fly content creation (not node) and caching

[Jean-Michel Pouré]

Le vendredi 01 janvier 2010 à 14:08 +0100, Ivan Sergio Borgonovo a
écrit :
> 
> Before just building my cache tables and build up my own cache
> system on top of cache API, is there an alternative approach? 

You may turn off caching, turn on SQL logging for slow queries and study
your SQL query log server-side in the SQL database. Find slow queries
and fix them. Of course, this may not be possible if you are using a
shared server without access to logs.

I wrote these guidelines if you are interested:
http://drupal.org/node/559302

Most Drupal developers are writing PHP code and take advantage of Drupal
caching system. The drawback is that we developers have no idea of the
actual time that SQL queries take to run.

If you are running MySQL on a dedicated server, consider dropping MySQL
because it is fairly slow. And look at PostgreSQL. when configured
correctly, it can be faster than the caching system. But this is my own
opinion, people with no SQL background may consider MySQL a nice tool
just because it runs queries.

Two months ago, I agreed to work on MySQL for a Drupal project. When
queries started to flow on the production server, I saw a number of red
lines indicating that MySQL was not working fast enough and thus dropped
transactions. When I migrated back from MySQL to PostgreSQL, some tables
had duplicated entries, just because users had clicked several times on
Submit button. I looked at MySQL table and they had unique indexes. This
is what MySQL does: it is only a desaster. It can work for small sites,
but when using large sites, you need a minimum of two servers, one for
database, the other for MySQL. And you go beyond 1000 simultaneous
users, you probably need a farm, which will ruin you. 

Now my contracts have the "No MySQL" obligation.
My opinion.

Kind regards and happy new year,
Jean-Michel
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