[Qgis-user] Snapping tools really slow
philipb at pembrokeshirecoast.org.uk
Fri Jan 22 05:38:40 PST 2021
What sort of database are you using? MSSQL or Postgres?
We're on Postgres13 and PostGIS 3.0. A quick test with QGIS 3.10.14 digitising to OSMM... there is a small delay but its only around a second or two. You may have a larger extent than me in your database though? Mine is just the whole of the County of Pembrokeshire. I haven't tried 3.16 to see if there is any noticeable difference.
From: Qgis-user <qgis-user-bounces at lists.osgeo.org> On Behalf Of Paul Wittle
Sent: 22 January 2021 08:10
To: Julien Cabieces <julien.cabieces at oslandia.com>
Cc: qgis-user at lists.osgeo.org
Subject: Re: [Qgis-user] Snapping tools really slow
It might be best if I screen record you a video of it loading so you can see the performance issue as it is always difficult to discuss in text. I'll have to send that to you offline from this thread as I believe videos aren't supported by this group.
We are snapping to Ordnance Survey MasterMap because we work in the public sector and are permitted to do so for council business. Depending on licencing you may not be able to access the same level of OS data as you would probably have to pay for it (assuming your company is private) so I guess that would not be helpful in terms of replicating the issue. That said; I also tried it using the OS Maps API (WFS) and it was also slow so OS may be able to share that with you for test purposes.
In the older version 3.10 the progress bar always disappeared for some reason so it appeared to just hand whilst the index builds. In the new version a blue bar appears at the bottom but it is not a loading bar it is the one you get when the application doesn't know how long is left. I tried to stop the process because it was long running and it said 'Indexing' was running did I want to try and stop the process so I'm pretty sure it is the indexing that is not working for some reason.
Is there a way to pre-build the snapping index?
It works fine for smaller layers, things we create etc. If I can resolve this one layer then all my problems go away so we would be really happy to pre-cache the snapping index if that is possible.
From: Julien Cabieces <julien.cabieces at oslandia.com>
Sent: 22 January 2021 05:32
To: Paul Wittle <P.Wittle at dorsetcc.gov.uk>
Cc: qgis-user at lists.osgeo.org
Subject: Re: [Qgis-user] Snapping tools really slow
I made quick tests with some dataset and I failed to see any performance issues.
Could you create an issue with some data sample and project?
Is it the index building that take a long time (there is a progress bar displayed at the bottom of the map close to the mouse coordinate information while index is currently building) or is it when you move your cursor on the map that the snaping information takes time to appear. Or is it when you pan the map?
You can enable snapping for specific range of scale, avoiding building index at very large scale where snapping is useless.
> I've been using version 3.10 and 3.16 and I notice that enabling snapping is extremely slow and oddly significantly slower on 3.16 than 3.10. We thought it might be downloading the dataset on screen but discovered the data is back from the database within seconds and the delay is because QGIS is building an index.
> Why is it so inefficient and is there anything that can be done to get better performance?
> It is really slow and we are trying to transfer users from MapInfo / ESRI so they will not like the performance at the moment.
> To be clear the data has a primary key, spatial indices and all is of good quality. As I say the data downloads and displays within seconds on the map; is it because I've selected snapping to segment as well as vertex?
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