[Qgis-developer] [Qgis-user] QGIS loaded millions of entries

[Nyall Dawson]

On 4 March 2017 at 18:41, Alessandro Pasotti <apasotti at gmail.com> wrote:
> On Sat, Mar 4, 2017 at 9:25 AM, Nathan Woodrow <madmanwoo at gmail.com> wrote:
>>
>> Hmm are you sure we don't do this already?
>>
>> I suspect we do. Each provider can handle the sorting, giving to it by
>> QgsFeatureRequest, and hand the results back to the caller.  I thought the
>> attribute table was already implemented this way.
>>
>> Regards,
>> Nathan
>
>
> Hi,
>
> IIRC the last time I looked into it (way more than 1 year ago) the
> sorting/filtering on PostGIS was not yet implemented on the back-end, that's
> why the provider (invoked from the attribute table) was fetching all the
> records.
>
> Please correct me if I'm wrong, but I think that the sorting/filtering is
> now implemented in the backend (at least for PostGIS, not sure about the
> status of every provider)

Filtering yes, sorting no.

Every provider has *some* functionality for filtering on the provider
side, but with different levels of compatibility. Most providers
(exception of oracle and mssql) we've pushed this about as far as we
can, and the remaining expression functions just can't be mapped
across.

> but the attribute table will still fetch all
> records unless you limit the view to the map/project extent.

A change I just pushed to master also prevents this full table load if
you use the "show selected features" mode. So that helps a bit.

Nyall