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On Sat, Oct 12, 2013 at 1:37 PM, Peter Brown <[email protected]>wrote: > Dear Alexandre > Sorry I have not replied before, but your suggestions have set me off on a > new voyage of discovery. It has been exceeding helpful, so thank you very > much > Regards > Peter > > > On 7 October 2013 16:33, Alexandre Neto <[email protected]> wrote: > >> Hello Peter, >> >> I'm not a database expert whatsoever, and there are better people in this >> list to clarify this. I just stated my experience with it. >> >> As far as I know, in order to respect Postgres Primary keys, QGIS uses >> the columns default values. >> >> If during the table creation your primary keys were created with >> something like: >> >> CREATE TABLE yourtable >> ( >> gid serial NOT NULL, >> ... >> ) >> >> Then, a sequence 'yourtable_gid_seq' is created and the default value >> for your gid column is set to nextval('yourtable_gid_seq'::regclass) >> >> When a new feature(row) is created if the user does not fill the pk field >> (and he is not supposed to), postgres will consider the default value, give >> it the next not use value from the sequence and update the sequence. >> >> If you are using QGIS, when you create a new feature or simply split an >> existing features, make sure not to type anything in the PK field, or this >> will give you a bad time. Just leave it blank, during the save\commit, both >> QGIS and Postgres will know what do do with it. >> >> Not sure where all this knowledge came from, but have a look here: >> http://www.postgresql.org/docs/9.1/static/functions-sequence.html >> >> Best regards, >> Alexandre Neto >> >> >> On Mon, Oct 7, 2013 at 3:59 PM, Peter Brown <[email protected]>wrote: >> >>> uummmm >>> Reading your answer {particularly the bit about a >>> nextval('yourtable_gid_seq'::regclass),} I realise that this bit of >>> code is an area of knowledge that I am missing, and clearly if it will >>> solve my problem then it would be useful. I wonder if I could ask you to at >>> least point me in the right direction. >>> I am fairly new to QGIS but generally a power user of databases, so I >>> have read the excellent manual >>> http://workshops.opengeo.org/postgis-intro/creating_db.html >>> and the more fundamental one at >>> http://www.postgresql.org/docs/9.2/interactive/sql.html >>> However, I do not seem to have come across anything like this. Can you >>> advise me? >>> Thank you for your help >>> Regards >>> Peter Brown >>> >>> >>> On 7 October 2013 11:09, Alexandre Neto <[email protected]> wrote: >>> >>>> Hello, >>>> >>>> I'm not sure If I followed your question, but in my experience with >>>> QGIS editing Postgres\postgis spatial tables, I add some smal hickups, but >>>> never with splitting. >>>> >>>> If its a normal polygon and you wish to split it with a line, QGIS will >>>> assign to all your new polygons a nextval('yourtable_gid_seq'::regclass), >>>> and this should solve the PK's problem. >>>> >>>> If it's a multipart polygon that you want to spit it's parts, you can >>>> use the multipartsplit plugin, and it will also take care of your primary >>>> keys. >>>> >>>> Maybe it's a problem with your table, please send the creation SQL >>>> command and maybe someone can have a clue of what is happening. >>>> >>>> >>>> >>>> On Mon, Oct 7, 2013 at 10:41 AM, Peter Brown >>>> <[email protected]>wrote: >>>> >>>>> Thanks for your prompt response, it is nice to know that it is >>>>> possible, but the methods you remember do seem to have problems. >>>>> - in QGIS I can split a polygon which is on a layer, and under the >>>>> 'layer' option on the menu, I call up the attributes table, but that only >>>>> offers me all the fields in the base PostGIS table EXCEPT (a) the ID >>>>> and >>>>> (b) the geometry >>>>> - I have tried manufacturing another PostGIS table with all the >>>>> attributes of the polygon except an ID field with all its 'NO NULLS' etc, >>>>> but then when I open a layer in QGIS it draws the polygon but shows it as >>>>> not editable >>>>> You have obviously managed something clever, but I am not quite sure >>>>> what >>>>> Regards >>>>> Peter Brown >>>>> >>>>> >>>>> On 7 October 2013 09:32, Hugues François <[email protected]>wrote: >>>>> >>>>>> ** >>>>>> Hello, >>>>>> >>>>>> I previously edited polygons from postgis within qgis and with no >>>>>> problem. If I remember well, before saving I also filled attribute data >>>>>> to >>>>>> give a new ID. Maybe if you just want to edit polygons without changing >>>>>> attributes, you may remove constraints on your postgis table (especially, >>>>>> uniques, not null and primary key) before editing (and then put the >>>>>> things >>>>>> right back to postgis). >>>>>> >>>>>> Hugues. >>>>>> >>>>>> >>>>>> >>>>>> ------------------------------ >>>>>> *From:* [email protected] [mailto: >>>>>> [email protected]] *On Behalf Of *Peter Brown >>>>>> *Sent:* Monday, October 07, 2013 9:53 AM >>>>>> *To:* [email protected] >>>>>> *Subject:* [postgis-users] Saving a split polygon >>>>>> >>>>>> In Quantum GIS (QGIS) there is a very useful facility for taking a >>>>>> polygon in a PostGIS database linked to QGIS and splitting it. HOWEVER, >>>>>> when one then tries to save the two portions, PostGIS puts up an error >>>>>> message that it cannot save the new portion because it does not have a >>>>>> new >>>>>> ID (it can save the existing portion, because this is only an edit of an >>>>>> existing ID). >>>>>> There are workarounds for this (e.g. convert to 'Shape' files) but >>>>>> they seem incredibly clumsy. Does anyone have a more direct solution? >>>>>> Thanks >>>>>> Peter Brown >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> postgis-users mailing list >>>>>> [email protected] >>>>>> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >>>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> postgis-users mailing list >>>>> [email protected] >>>>> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >>>>> >>>> >>>> >>>> _______________________________________________ >>>> postgis-users mailing list >>>> [email protected] >>>> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >>>> >>> >>> >>> _______________________________________________ >>> postgis-users mailing list >>> [email protected] >>> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >>> >> >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >> > > > _______________________________________________ > postgis-users mailing list > [email protected] > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >
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