Ok, I'll take a look and monitor the queries from QGIS 2 and 3 and report back. It will take a couple of days
And thanks Nyall Den tor. 6. dec. 2018 kl. 11.54 skrev Nyall Dawson <[email protected]>: > On Thu, 6 Dec 2018 at 20:34, Bo Victor Thomsen > <[email protected]> wrote: > > > > Hi Nyall - > > > > I'm running QGIS 3.4.2 on Windows ver.10. > > > > > > > > Have there been any other changes to the SQLServer driver besides the > validity check? (I remember vaguely something about the internal > representation of spatial objects in the driver) > > No, nothing that would explain this. Just minor bug fixing and the port to > Qt 5. > > I wonder if you could log the queries coming from QGIS and see if you > can identify any changes from 2.18? > > Nyall > > > > > > > > I'm asking, because I've done this type of testing QGIS 2.x before where > the time difference between Postgres and SQL Server was relatively small > when doing simple MBR based searches - somewhere in the vicinity of 20% > > > > > > > > I would happily ditch MS SQLServer forever for spatial work and mainly > use Postgres. However, my customers have a different opinion :-( > > > > Den tor. 6. dec. 2018 kl. 11.17 skrev Nyall Dawson < > [email protected]>: > >> > >> On Thu, 6 Dec 2018 at 20:05, Bo Victor Thomsen > >> <[email protected]> wrote: > >> > >> > I've tried switching the validity check off as described. As far as I > can measure, there is no time difference with or without the validity > check. When does the validity check kick in? Writing or reading the > features? Or both? > >> > > >> > >> It's on read. Writing always uses a make valid call for SQL Server to > >> try to avoid triggering the issue. > >> > >> > And the validity check doesn't explain the obvious time difference > between the OGR driver and the native QGIS driver for SQL Server > >> > >> Well, it would if OGR wasn't doing this check by default. What > >> platform are you connecting from? Windows or Linux? > >> > >> > However, I will use your explanation about SQL Server's behavior > regarding invalid geometries as an argument for my customers to switch to > Postgres instead of using SQLServer :-) > >> > >> There's also these points: https://www.pg-versus-ms.com/ (I think I > >> could write as much again on the spatial side of things alone.) If you > >> have a choice, Postgres is far superior in so many ways. > >> > >> Nyall > >> > >> > > >> > > >> > > >> > > >> > Den tor. 6. dec. 2018 kl. 10.17 skrev Nyall Dawson < > [email protected]>: > >> >> > >> >> On Thu, 6 Dec 2018 at 19:05, Bo Victor Thomsen > >> >> <[email protected]> wrote: > >> >> > > >> >> > Hi list - > >> >> > > >> >> > > >> >> > > >> >> > I've done some experiments with a dataset consisting of 440000 > rows and uploaded this to two database servers: Postgres and SQLServer. > Both tables has indexes on Primary key and the spatial column. > >> >> > > >> >> > > >> >> > > >> >> > And then connected to both tables in QGIS. The SQL server is 3 > times slower in retrieving the dataset than Postgres in QGIS! > >> >> > > >> >> > >> >> It's probably the extra validity checks which were added. SQL Server > >> >> itself is broken by design when it comes to spatial data handling and > >> >> if it encounters an invalid geometry it will silently abort the > >> >> request and you'll be missing features from the layer. But there's > *no > >> >> way* for QGIS to detect when this occurs! Accordingly QGIS takes the > >> >> "safer is better" approach and forces a validity check and make valid > >> >> step as part of the queries sent to SQL Server. This avoids the > >> >> potentially missing features, but comes at a large cost. > >> >> > >> >> If you're 100% sure that your tables have no invalid geometries (and > >> >> never will have any!), you *can* switch this check off. But be > >> >> warned... if you ever introduce invalid geometries into your tables, > >> >> you'll get data loss. The setting is under the SQL Server > connection's > >> >> properties -- "skip invalid geometry handling". > >> >> > >> >> Let me know if this helps at all > >> >> > >> >> Nyall > >> > > >> > > >> > > >> > -- > >> > Med venlig hilsen > >> > > >> > Bo Victor Thomsen > >> > > > > > > > > > -- > > Med venlig hilsen > > > > Bo Victor Thomsen > > > -- Med venlig hilsen Bo Victor Thomsen
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