>-----Message d'origine-----
>De : Jesse Sheidlower [mailto:jes...@panix.com]
>Envoyé : jeudi, 10. janvier 2013 16:16
>À : catalyst@lists.scsys.co.uk
>Objet : [Catalyst] DB values that change very rarely
>In one of my apps, I have a number of tables that contain values that
>change very rarely. 
>This means that almost every page generation hits the database a whole bunch of
>unnecessary times, and that all of my controllers are cluttered.
>This must be a fairly common problem. What's the best way to deal with
>it--both the desire to persist what is mostly static data, and to keep
>my controllers clean?

Hi Jesse,

First of all, you need a piece of information that tells you if the 
configuration data has changed. It can be a version number or a timestamp 
column, either associated to each table (if these tables change individually), 
or in a global "version table" that covers everything. Every time that a power 
user edits such data, your version number or timestamp must be updated. 

Or maybe all this configuration data that doesn't change very often could be 
stored, not in database, but in a config file (using YAML, XML, or 
Config::General). In that case you have the mtime of the file to tell you if 
the data has changed.

Based on this, your controller can use any of the CPAN caching modules to keep 
the data in memory; you still need to go to the datasource to check if the 
version number or timestamp has changed, but that's a much smaller request.

Another way would be to exploit the caching functionality of the browser 
itself. In that case, the configuration data should be at a separate URL, like 
/myApp/config.json. Every page should use client-side javascript to exploit the 
config.json data (for exemple for building the various OPTIONS of a SELECT). 
Each page of the application loads /myApp/config.json, either through a <script 
src="...">, or through an Ajax call.The controller that serves this config.json 
should implement conditional GET, i.e. read the "If-Modified-Since" or 
"If-None-Match" headers, ask the datasource for its timestamp, and return 302 
NOT MODIFIED if the client tag is in sync with the server data. That's a 
client-server round trip, but it's very fast because there is almost no content 
to be exchanged. Furthermore, the advantage is that the /config.json data is 
shared among all pages of your app -- it only travelled once from the server to 
the client.

Hope this helps -- good luck,

 Laurent Dami

List: Catalyst@lists.scsys.co.uk
Listinfo: http://lists.scsys.co.uk/cgi-bin/mailman/listinfo/catalyst
Searchable archive: http://www.mail-archive.com/catalyst@lists.scsys.co.uk/
Dev site: http://dev.catalyst.perl.org/

Reply via email to