AW: Re: [Qgis-user] New PostGIS SQL Query Editor Plugin
tschaun
hartmut.tschauner at gmail.com
Thu Mar 12 16:02:08 PDT 2009
Horst,
I had been waiting for a plugin such as yours for quite some time; all the
analytical power of PostGIS spatial SQL right on the desktop -- terrific.
Thanks for making this functionality available. I have one problem to report
and one suggestion.
The problem: while your plugin runs fine on Ubuntu, it crashes on my Windows
system. The error message is:
An error has occurred while executing Python code:
Traceback (most recent call last):
File
"C:/Users/Hartmut/.qgis//python/plugins\postgisquery\PostgisQuery.py", line
138, in anzeigenVLayer
stderr=subprocess.PIPE
File "C:\OSGeo4W\apps\Python25\lib\subprocess.py", line 587, in __init__
errread, errwrite) = self._get_handles(stdin, stdout, stderr)
File "C:\OSGeo4W\apps\Python25\lib\subprocess.py", line 700, in
_get_handles
p2cread = self._make_inheritable(p2cread)
File "C:\OSGeo4W\apps\Python25\lib\subprocess.py", line 745, in
_make_inheritable
DUPLICATE_SAME_ACCESS)
WindowsError: [Error 6] The handle is invalid
Python version:
2.5.2 (r252:60911, Feb 21 2008, 13:11:45) [MSC v.1310 32 bit (Intel)]
The suggestion: I second the suggestion made by a previous poster of using a
view for data caching, or perhaps a Sqlite/Spatialite database. The
column-name limitations of Shapefiles are extremely annoying, to say the
least. They might even cause serious problems when multiple column names
receive identical abbreviations (as they did in PgArc; please forgive me if
your code takes care of this, I haven't read it line by line).
Thanks again for an extremely welcome contribution. I anxiously await a
fix/explanation of the Windows problem.
Regards,
Hartmut
Düster 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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