On Feb 14, 6:02 pm, Jonathan Vanasco <[email protected]> wrote:

> 3. i haven't figured out yet if its possible to handle multiple db
> connections in pyramid.  in pylons i have "sqlalchemy.write.url" and
> "sqlalchemy.read.url" and handle multiple databases due to master/
> slave clustering.  in order to get widespread appeal, something like
> this needs to be very apparent and easy to do - Rails accomplishes
> this in a few lines of configs.

Turns out to be really easy.  I had nearly figured it out myself in
about 20 minutes of poking around but was still slightly stuck, when I
happened to re-read Mike's "Pyramid Migration Guide" :
https://bytebucket.org/sluggo/pyramid-docs/wiki/html/migration.html.

In your config file you just add additional prefixes.  For example the
default sqlalchemy prefix is "sqlalchemy."  You could have a two-
engine scenario by making up any two prefixes, say, "sqlalchemy1." and
"sqlalchemy2." ... or "spam." and "eggs."  You also set up multiple db
URIs instead of just one, so there's where you prepare to point your
different engines at different databases, potentially even with
different user accounts, etc.

Then in the place where the basic pyramid template instantiates a
database engine, you instantiate two or more, as needed.  And where
the basic template initializes one set of model classes, you go ahead
and import two or more sets of model classes, whatever you need to do
to tie down whatever ORM or other database handling code that is
needed.

All in all it was like 30 minutes from when I asked myself that same
question - "so how do I open two DBs at once with this so I can get
some transitional and migration work done?" - to the time I had both
my old and new databases running side by side.  And I'm not exactly
the quickest on picking up new paradigms, often needing more examples
that I would like to admit.

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