[Qgis-developer] QWC and WMS FILTER in qgis mapserver

Alessandro Pasotti apasotti at gmail.com
Mon Jan 13 01:06:29 PST 2014

2014/1/12 Marco Hugentobler <marco.hugentobler at sourcepole.ch>

>  Hi Alessandro
> >in WFS we have the standard OGC "FILTER" plus the  QGIS custom
> >in WMS we have QGIS custom "FILTER"
> >
>  >IMHO the best solution would be to have the same parameters also in
> WMS, so:
>  >
>  >rename WMS QGIS custom  "FILTER" to "EXP_FILTER" and
> >implement OGC  "FILTER" even if it's not in the standard
>  Oh, so we have even three filter possibilities:
> 1. OGC Filter (done via QgsExpression )
> 2. Filter with QGIS custom syntax (done via QgsExpression)
> 3. Filter with provider subset with syntax of data provider (e.g. SQL).
> Done on provider (DB) side for very fast searches, therefore needs careful
> parsing against SQL injections
> WFS server implements 1+2, WMS server implements 3. There are pros and
> cons for all of them, so it would be nice to have three parameter name to
> call all of them for WMS servers.
> >Do you think that we can re-use the WFS OGC FILTER code for the WMS OGC
> FILTER implementation?
> QgsOgcUtils::expressionFromOgcFilter
Thanks Marco, now I hope I've got the whole picture.

Can we agree on the parameter names to use for those calls?

The only one which is in the official specs is WFS "FILTER", then we have
implementations for

QGS Exp. filter WFS="EXP_FILTER"
QGS provider filter  WMS="FILTER"

I'm proposing this:

OGC Filter  WFS="FILTER", WMS="FILTER" (to be implemented)
QGS Exp. filter WFS="EXP_FILTER", WMS="EXP_FILTER" (to be implemented)
QGS provider filter  WFS="PRO_FILTER"   (to be implemented),
 WMS="PRO_FILTER" (to be renamed)

... I don't have any better idea for  PRO_FILTER but still don't like it,
any hint?

Note that this will break existing apps, if we are renaming the WMS FILTER
to PRO_FILTER (or something else)

Alessandro Pasotti
w3:   www.itopen.it
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