[QGIS-Developer] Whatever is wrong with QGIS 3.x SQL server driver

[Bo Victor Thomsen]

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!



And it's not SQL server's fault!! I've made the same experiment using
GeoServer as a client where Postgres is only slightly faster.



To make matters worse... In QGIS you can connect to the SQL server database
using the "Layer" > "Add Layer" > "Add Vector layer" - i.e. using the OGR
driver - to connect to the SQL Server table. This makes the retrieval of
SQL Server data nearly as fast as Postgres.



I have to conclude, that the native QGIS SQLServer driver is really, really
bad. What's the matter with this driver?



I recollect, doing the same experiment in QGIS 2.x, that a simple fetch of
SQL server data was nearly as fast as retrieving data from a comparable
Postgres database server (I’m not talking about complex spatial queries,
where Postgres blows SQL Server totally out of the water, but simple
retrieval of layer data using a MBR search)



Unfortunately, I can't just switch to the OGR driver since I have some
write issues with this driver.



What gives ???



-- 

Med venlig hilsen



Bo Victor Thomsen
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