[Qgis-user] updating postgres updateable view much slower from attribute table than using db manager

[Janneke van Dijk]

Hi Nyall,

Tested it with 12.1.1, that doesn't make a difference as far as I can 
tell (40 minutes now). I tested the view without the many joins for 
lookup values (it had about 13 joins and reduced it to 4), which made it 
take around 15 seconds, which would be acceptable. I haven't yet tested 
if it may be one specific join that causes the behaviour or that it is 
the number of joins.

I'm still curious to understand what the difference is between the 
update statement in the db manager and the way the data are updated from 
the attribute table. Could it be that the update via db manager only 
needs to 'calculate' the joins once, where the update via the attribute 
table has to loop through all the selected features, 'calculating' the 
joins for every record that needs to be saved? If that is the case, 
would there be a way to bypass this behaviour (by using the original 
where clause for making the selection maybe)?

greetings,
Janneke

On 28/11/2015 01:42, Nyall Dawson wrote:
>
>
> On 27 Nov 2015 10:18 PM, "Janneke van Dijk" <janneke.qgis at gmail.com 
> <mailto:janneke.qgis at gmail.com>> wrote:
> >
> > Dear list,
> >
> > I have an updateable spatial view in Postgres loaded into QGIS 2.10. 
> When I update 6999 records in this view in the db manager with the 
> following statement:
> > update v_prepare_assessment_id SET districtid = 8 where locationid > 
> 13000 and locationid < 20000
> > it takes 2.7 seconds to complete.
> >
> > When I open the attribute table, select the same records, then use 
> the update bar in the top to update the districtid to 8, using 'update 
> selected' , then save edits, it takes more than 10 minutes (after 
> which I closed the project).
> >
> > Doing the same update directly on the attribute table of the 
> underlying postgres table works nicely (takes about 3 seconds) after 
> save edits.
> >
> > Does anyone know why the update via the attribute table on the view 
> takes so long as to be unusable, while the db manager works nicely 
> with the view? Seeing that working directly on the underlying table 
> from the attribute table works well too it's seems to be a combination 
> of the attribute table approach with an updateable view that seems to 
> cause the issue.
> >
> > Thanks for any thoughts on the matter,
>
> Please try with 2.12.1 or the current nightly snapshots.
>
> I made a change since 2.12 which may have improved this already.
>
> Nyall
> >
> > Janneke
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