Does QGIS import SQL Server data or query it?

Question

I have a SQL Server DB with about 200GB of various datapoints stored on server.

When I use this datasource in QGIS from my PC would all the data be imported?

I.e do I need to make sure I have 200GB free on my device to render the information?

For Postgres, rendering is done by fetching the geometry + primary key only. If you need attributes of a single entity (the info tool), it is fetched by ID. The bottleneck occurs if you open the attribute table, as the entire table gets loaded in memory. To reduce the impact, make sure that by default, only the features in the extent are loaded in the attribute table. — JGH, Commented Jan 27, 2022 at 13:58

user30184 · Accepted Answer · 2022-01-27 07:26:59Z

QGIS does not make local copy of data from any data source and least of all from the database sources. However, that is so self-evident that I could not find any reference that directly says so. Perhaps https://docs.qgis.org/3.16/en/docs/user_manual/plugins/core_plugins/plugins_db_manager.html#dbmanager gives a hint that access to databases is using query-what-you-need principle. Or maybe you want to have a look at the internals of the MSSQL provider https://github.com/qgis/QGIS/blob/master/src/providers/mssql/qgsmssqlprovider.cpp

1 Answer 1