On Wed, Sep 26, 2012 at 2:25 PM, Ryan Lane <rlane(a)wikimedia.org> wrote:
We currently have no plans for having the user
databases on the same
servers as the replicated databases. Direct joins will not be
possible, so tools will need to be modified.
This is unfortunate, and a huge step backwards from the situation on
the toolserver.
For example, the project I maintain on toolserver (the enwiki WP 1.0
assessment data) has user database tables with several million rows of
data about articles, from which it needs to select the data for pages
from fixed categories on the wiki, which themselves could have a few
thousand members. The natural way to do this is to join against the
categorylinks table. Any non-join solution is going to be much, much
less efficient.
A key role of the toolserver setup was that it allowed these sorts of
joins. Web hosting is cheap and data about the live wiki is already
available in non-joinable form through the API with no replag.
- Carl