[mapserver-users] querying WMS layer / WFS reprise

[Gregor Mosheh]

> I don't think WFS queries should be inherently slow.
...
> I think you need to examine what you are doing more closely to see if:
>   o the resultset is very large (dump response to file and inspect size)
>   o the query being done by MapServer is expensive.  Some WFS geometric
>     queries may be expensive to check.  MapServer is generally not terribly
>     fast at attribute queries as far as I know.
>   o The MapServer query architecture requires that each query result be
>     fetched individually by id after a first pass to build a list of ids for
>     features that satisfy the request.   This kind of read is very slow
>     against some datasources (ie. some OGR drivers).

The queries were being done directly to the WFS server (telnet localhost
80), too, not via a MapServer WFS client. It wasn't a matter of the data
taking a while to transfer: there was simply no activity for several
minutes, and then the data came across. It was definitely something
"inside" the WFS server, as opposed to the rendering or transit of the
data.

The result sets weren't very large: 20 or less multipolygons (zipcode
areas). A fair chunk of data, but it's over a LAN. The same query via WMS
responded in 1-2 seconds, indicating that it's the WFS stuff, as opposed
to the underlying data, that's taking the time.

Today's experiment is to try out GeoServer and see what its performance is
like for WFS and WMS. I'll let y'all know.