MS RFC 22: Data adapter support

[Umberto Nicoletti]

On 10/23/06, Stephen Woodbridge <woodbri at swoodbridge.com> wrote:
> Tamas Szekeres wrote:
> > Folks,
> >
> > According to the mapserver 5.0 development plan
> > http://mapserver.gis.umn.edu/development/release_plans/mapserver_5_0
> > we have planned to implement feature cache support for long running
> > processes and query processing. This support will increase the
> > performance of the long running processes by maintaining the features
> > from a previous query in an internal memory cache.
> >
> > The first step to implement this feature is to provide a framework to
> > modify the behaviour of the  existing providers in an unified manner.
> > The changes described in RFC 22 will address this issue.
> >
> > http://mapserver.gis.umn.edu/development/rfc/ms-rfc-22
> >
> > Any comments and suggestions will be appreciated.
> >
> > Best Regards,
> >
> > Tamas
>
> Tamas,
>
> This is a great writeup. It is very clear and easy to follow.
>
> Have you thought about the caching mechanism at all? I would like to
> suggest that you look at memcached. This is a very simple memory based
> caching mechanism that is key=value driven and uses a least recently
> used flushing along with other methods of expiring cache items. You can
> open a socket connection to a pool of memcached servers, and the api
> handles the rest. We you md5 digest hashes of the request for the keys
> which works very nicely with complex requests like xml, perl structures,
> SQL queries etc.

I have tried plugging memcached into an oracle spatial layer to
improve performance of mostyle static data, but I have found out that
it is slower than oracle: memcached C api only works for strings so I
tried to convert shapes to WKT geometries but the whole back and forth
conversion process is slower than fetching the data directly from
oracle.
Drawing from the cache was 2x slower than accessing oracle directly.
Maybe this difference would be lower in BUSY oracle installations?

I should still have the code somewhere (I tried this summer) so I can
post it if someone wants to take a look.

Umberto

>
> This could be configured to get from the cache or make the mapserver
> query and store the results to the cache.
>
> There are a lot of large sites using this to cache sessions and/or
> database queries with great results, there is an active list for support
> and fixes and it is an OpenSource project.
>
> Anyway, I'm associated with them, but please look it over if you are not
> already familiar with it.
>
> -Steve W.
>