AW: Re: [Qgis-user] New PostGIS SQL Query Editor Plugin

Fri Mar 13 00:43:23 PDT 2009

Hi Horst,

Thanks for providing this useful plugin.

Following the discussion I suggest that you try using the MemoryProvider
instead of Shapefiles. In many cases, one doesn't want to store the
results of the query - so the memory provider would be a good place for
the temporary storage of the result.

If the user wants to store the results he can still write it to a
shapefile or to Postgis.

Here is some sample code for the MemoryProvider:
http://wiki.qgis.org/qgiswiki/PythonBindings
(search for memory provider)

I haven't used it myself, but it looks like a perfect thing to use for
your plugin.

Andreas

On Thu, March 12, 2009 9:25 pm, DÃ¼ster Horst wrote:
> John,
>
> I created the plugin due to the lack of possibility to visualize PostGIS
> SQL Queries with resultant tables containing geometry columns. In
> principle it should have a similar behaviour like the PgAdmin3 SQL
> Editor. With the difference that the new plugin creates a geographical
> view at the result too.
>
> Mini docmentation:
> 1. You have to define a PostGIS connection with the PostGIS Connector
> 2. When you start the plugin for the first time, it will ask for a
> temp-path because it has to store the resultant shape files into a
> directory. For further sessions this directory will be used until you
> change it with the ... button
> 3. select the former defined PostGIS connectin
> 4. Under the assumption you have a PostGIS Table called example with one
> geometry-column you can use the plugin to execute the following query:
>
> select * from example
>
> when you hit the execute button or alternatively F5 the query is
> executed and it produces a shape-file with the query result. But my
> simple example doesn't make much sense. The use of the plugin makes
> sense when you develop complex queries with joins, aggregations, filter,
> functions etc. In this case you are able to develop your query and to
> view the result directly and very easy. I think it is very helpful.
>
>>Also, the plugin asks for a temporary directory to store files in, but
> it seems that you need a permanent directory to work from. This is where
> I am confused. Is this meant to perform queries on >existing postgis
> tables, or is it meant to query a shapefile and then load it into
> postgis? If the former, how does it improve on adding a postgis layer
> and performing the query there?
> In many cases when you develop spatial queries it is helpful to see the
> result directly. Thus you have to save the query-result temporarily many
> times until you have finished the development process. Than you can take
> your query and make a view from it into the database, which you can load
> directly from PostGIS via Postgres connector of course. The idea is to
> have a developement tool it is not the idea to create persistent
> queries. If you like to save your temporary query result to a non
> temporary place, please use the QGIS save as shapefile command.
>
> I hope that the intension and the use of the plugin will be a little
> more precised.
>
> Regrads
> Horst
>
>
> ------------------------------------------------
>
> Dr. Horst Düster
> Stv. Amtschef / GIS-Koordinator
>
> Kanton Solothurn
> Bau- und Justizdepartement
> Amt für Geoinformation
> SO!GIS Koordination
> Rötistrasse 4
> CH-4501 Solothurn
>
> Telefon ++41(0)32 627 25 32
> Telefax ++41(0)32 627 22 14
>
> mailto:horst.duester at bd.so.ch
> http://www.agi.so.ch
>
>
>
>    -----Ursprüngliche Nachricht-----
>    Von: John C. Tull [mailto:john.tull at wildnevada.org]
>    Gesendet am: Donnerstag, 12. März 2009 17:47
>    An: Düster Horst
>    Cc: qgis-user
>    Betreff: Re: [Qgis-user] New PostGIS SQL Query Editor Plugin
>
>
>    Düster,
>
>    Do you have any documentation on how to use this? I gave it a go this
>    morning, but a simple query statement did not work. What would be a
>    snippet that would work in the query editor given that one has a
>    table called "example" in a database called postgis with public
>    schema on a local server?
>
>
>    Also, the plugin asks for a temporary directory to store files in,
>    but it seems that you need a permanent directory to work from. This
>    is where I am confused. Is this meant to perform queries on existing
>    postgis tables, or is it meant to query a shapefile and then load it
>    into postgis? If the former, how does it improve on adding a postgis
>    layer and performing the query there?
>
>    Cheers,
>    John
>
>    On Mar 12, 2009, at 1:36 AM, Düster Horst wrote:
>
>
>
>       I just uploaded the new PostGIS SQL Query Editor Plugin to the
>       QGIS User-Contributed Python Plugin Repository. The aim of the
>       plugin is to edit and perform any spatial PostGIS query from an
>       editor environment. After successful execution of a query the
>       result will be loaded from shape file to MapCanvas. The plugin
>       works provided that pgsql2shp is installed and the path to
>       pgsql2shp is defined in the system PATH environment.
>
>       I hope that the plugin will be helpful for you. I'm looking
>       forward for any comment.
>
>       Regards
>
>       Dr. Horst Düster
>       Stv. Amtschef / GIS-Koordinator
>
>       Kanton Solothurn
>       Bau- und Justizdepartement
>       Amt für Geoinformation
>       SO!GIS Koordination
>       Rötistrasse 4
>       CH-4501 Solothurn
>
>       Telefon ++41(0)32 627 25 32
>       Telefax ++41(0)32 627 22 14
>
>       mailto:horst.duester at bd.so.ch
>       http://www.agi.so.ch
>
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>
>
>
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-- 
Andreas Neumann
http://www.carto.net/neumann/
http://www.svgopen.org/