[Qgis-user] QGIS 2.10.1 adding PostGIS Views

[Matthias Kuhn]

On 09/01/2015 05:54 PM, James Keener wrote:
> We also need to ask what qgis is doing with this and why we need to
> bug the user about it at all.
>
> Why do we not big the user about tables without a primary key? If
> tables can be loaded without a pk, why can't views.
QGIS relies on feature ids for a lot of different things to
unambiguously identify features.

For tables there is a (also not optimal) ctid which can be used as
feature id:
http://www.postgresql.org/docs/8.2/static/ddl-system-columns.html

For views there is none (see
http://www.postgresql.org/docs/9.1/static/rules-views.html, section 37.2.4)
>
> Why can I select non-unique columns as primary keys and after loading
> the layer get no error?
Because a lot of things in QGIS rely on feature ids and see above why
the fallback which exists for tables does not work for views.
Especially - but not only - editing. See my proposal #4.
>
> Are these also bugs? Should I make (or find?) tickets for them?
>
> Jim
>
> On September 1, 2015 11:49:23 AM EDT, Matthias Kuhn
> <matthias at opengis.ch> wrote:
>
>     Hi,
>
>     I would like to second Andreas, what we need is an improvement in the UI
>     to make the user aware of the problem.
>
>     My proposal (please review and improve!!!!)
>
>     1. Let the user choose whatever table/view he likes. Don't disable any
>     items.
>     2. If there are tables without a PK open a second modal dialog with an
>     explanation of the problem and offer to select a pk from a combobox.
>
>     -------------
>
>     3. Optional: Add a button "search suitable pk" which looks for a
>     suitable unique column.
>     4. Optional: Add a selection "read-only" to the combobox and do some
>     row_number() or other black magic and warn the user with a big red
>     dialog that he's about to do something very dangerous, unreliable and
>     that his warranty is now very void.
>
>     Best,
>     Matthias
>
>     On 09/01/2015 05:36 PM, Andreas Neumann wrote:
>
>         Hi, I would regard the loading of layers from a database
>         something "relatively advanced". Normally I prepare ready to
>         use QGIS project to my users who edit and query our GIS data
>         where they don't have to bother with loading layers. But you
>         are correct that it can be different persons - the one who
>         creates the view and the ones who are loading them. You are
>         welcome to improve the situation/GUI, but please don't go back
>         to the old behavior where it is an assumption that the first
>         column in the list is always the primary key. Andreas On
>         01.09.2015 14:51, James Keener wrote:
>
>             Why are you assuming the user who created the view is the
>             one using QGIS? Jim On 09/01/2015 08:50 AM, Andreas
>             Neumann wrote:
>
>                 Hi, I agree with Jürgen - better let the user choose
>                 the pkey column. If the user knows how to create a
>                 Postgis View he also knows how to select a primary key
>                 column. Andreas On 01.09.2015 14:37, Jürgen E. Fischer
>                 wrote:
>
>                     Hi Sandro, On Tue, 01. Sep 2015 at 13:48:33 +0200,
>                     Sandro Santilli wrote:
>
>                         I agree with Luca this should have been better
>                         not backported to 2.8.3. Only proper bugs
>                         should be backported, and this was a
>                         (debatable) GUI enhancement, as far as I can
>                         tell. 
>
>                     We intend to only backport fixes and not bugs. ;)
>                     You were always supposed to select the key column
>                     - preselecting the first column was the bug (also
>                     debatable). And #11317 is a ticket that
>                     demonstrates there were unaware users. That the
>                     first column often happens to be the primary key
>                     and and the combobox is not lexically sorted is
>                     somewhat pure luck - and unless you avoid having
>                     the key verified (using "use estimated metadata"),
>                     keeping a wrongly select column will make the
>                     layer to insert invalid. But I agree that the
>                     tooltip that you get on disabled lines (not only
>                     for the key selection, but also geometry type and
>                     srid) might not be visible enough (but that IMHO
>                     would be just a GUI enhancement). Jürgen
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