Volker Wysk <v@volker> wrote:
> Adding versioning functionality would be much easier after switching to
> use of a DBMS instead of the filesystem, for the cache.
This is probably true. Keeping more than one version and looking up
the versions related by a given date will be easier.
> High quality open source DBMSes are widely available (MySQL, PostgreSQL),
> and easy to install (RPM, DEB, autoconf). So why not use them? This
> would give several advantages.
>
> - improved performance, both speed and space wise
I would doubt that it is any faster. Currently all that WWWOFFLE
needs to do is create a hash from the URL and open a file.
For size, perhaps it would be better than WWWOFFLE on a conventional
filesystem. With something like the reiserfs filesystem the WWWOFFLE
cache is already more space efficient.
> - New data components could easily be added as new attributes. No more
> cache format incompatibilities, only an "alter table ... add column
> ..." command instead. The additional attributes needed for
> versioning could be added, and queries on them could be performed. In
> general, the more complex the not-in-memory data becomes, the more
> advantageous it becomes to leave the storage management to a DBMS.
It is true, that cache format changes do tend to be disruptive.
I am not sure that it is totally transparent with a database though.
When you add some new types of meta-data you have a problem. You
could fill in the new meta-data entries for existing pages (may not be
possible since you don't have the data). Or you must handle the case
where the meta-data is not available for all pages.
The first of these is how WWWOFFLE handles cache format changes.
There is a convert-cache program that is run to add the new meta-data
or change the file format.
> - Data independence. Programs independent from WWWOffle could operate on
> the same database, even concurrently.
Currently this is true of the WWWOFFLE cache. More than one WWWOFFLE
process can access the cache at once. This has always been a design
goal.
--
Andrew.
----------------------------------------------------------------------
Andrew M. Bishop [EMAIL PROTECTED]
http://www.gedanken.demon.co.uk/
WWWOFFLE users page:
http://www.gedanken.demon.co.uk/wwwoffle/version-2.6/user.html
