[QGIS-Developer] Question on @atlas_featureid

[Andreas Neumann]

Hi Matthias,

Ok - this is the case here. ili2pg creates bigint pkeys. That explains 
why I see the "unrelated" internal pkeys from QGIS instead.

It would be really nice if we had an option to create normal "integer" 
pkeys with ili2pg instead of bigint. Other GIS (like Geomedia) had 
issues with bigint pkeys as well (at least in older versions).

In 99% of our cases bigint isn't necessary and the ranger of normal 
integer good enough.

I'll open an issue at ili2pg.

Thanks for you explanation, Matthias!

Andreas

On 2021-07-12 07:59, Matthias Kuhn wrote:

> Hi
> 
> It depends on the implementation in the data provider (and normally on 
> the data type for the primary key).
> 
> In the postgres case, (up to) 32 bit integer primary keys are normally 
> used as fid.
> With others like 64 bit integer, string or compound foreign keys it's 
> not possible to stick to this approach, so an internal fid to pk map is 
> generated by the provider at runtime.
> 
> 64 bit integers cannot be directly reused as fid because QGIS stores 
> fids internally with 64 bit, but reserves the (negative, -1, -2, ...) 
> half of the available values for new, uncommitted features.
> 
> Matthias
> 
> On Thu, Jul 8, 2021 at 11:50 AM Andreas Neumann <andreas at qgis.org> 
> wrote:
> 
> Ok - that explains it.
> 
> It is quite confusing that QGIS uses a different internal ID than the 
> primary key column of the database. Is there a technical reason for 
> this behaviour?
> 
> Andreas
> 
> On Thu, 8 Jul 2021 at 11:43, Alexandre Neto <senhor.neto at gmail.com> 
> wrote:
> 
> As far as I remember @atlas_featureid has always returned the same as 
> the $id in the attributes table, which is kind of the internal row 
> number.
> 
> Alex
> 
> A quinta, 8/07/2021, 10:35, Andreas Neumann <andreas at qgis.org> 
> escreveu:
> 
> HI Jürgen,
> 
> Yes - I provided the primary key column
> 
> Here is my data source string:
> 
> service='edit' authcfg=sogis00 key='t_id' srid=2056 type=Polygon 
> checkPrimaryKeyUnicity='1' 
> table="alw_strukturverbesserungen"."projekt_aggregiert_v" 
> (geometrie_convex_hull) sql=geometrie_bbox IS NOT NULL
> 
> @atlas_featureid returns something like an internal "row number" or 
> similar, but not the column "t_id" as defined in the data source 
> string.
> 
> Andreas
> 
> On Thu, 8 Jul 2021 at 10:42, Jürgen E. Fischer <jef at norbit.de> wrote: 
> Hi Andreas,
> 
> On Thu, 08. Jul 2021 at 10:30:08 +0200, Andreas Neumann wrote:
>> attribute(@atlas_feature,'pkey_name'), but it is a little more 
>> complicated
>> than @atlas_featureid - and I'm pretty sure that @atlas_featureid was 
>> using
>> the pkey column in th past?
>> 
>> My data source for the atlas coverage layer is a Postgis View.
> 
> It's probably not using the column you expect for the feature id.  Did 
> you
> specify the key column when adding the view?
> 
> Jürgen
> 
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