Are M code filtering done in the data source?

[wpf_]

If i just want to filter a table in query editor for just active records, is the filtering done in the data source before it sends the data over to BI, or is all the data sent over to BI first, then filtered in BI?

I was wondering if the more filtering i do in query editor would slow down my report.  Thanks 

[v-stephen-msft]

Hi @wpf_ ,

I think this is also related to your connection mode.

If it is the import mode, it will import all data into Power BI. Therefore, if your data is filtered before importing, the performance of the report will be better.

If the connection is DirectQuery. It is a direct connection to data source. Data will NOT be stored in Power BI model. Power BI will be a visualization layer, then query the data from data source every time.

And the last connection mode is Live connection. There's no Power Query in this mode..

Reference: DirectQuery, Live Connection or Import Data? Tough Decision!

Best Regards,

Stephen Tao

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

[wpf_]

@v-stephen-msft 

when i filter in power query editor, doesn’t that take resources and time to filter even though it is being done in data source? Or is that still more efficient then bringing all the data over?

[v-stephen-msft · Accepted solution]

Hi @wpf_ ,

When you filter in power query editor, it takes time and resources to filter. 

It's always recommended to filter your data in the early stages of your query or as early as possible. Some connectors will take advantage of your filters through query folding, as described in Power Query query folding. It's also a best practice to filter out any data that isn't relevant for your case. This will let you better focus on your task at hand by only showing data that’s relevant in the data preview section.

We recommend that you strive to achieve efficiency in your model designs by ensuring query folding occurs whenever possible.

Best Regards,

Stephen Tao

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

[jthomson]

I think where the filtering is done depends on the type of data source you're using, and whether the manipulations you're doing support query folding.

In terms of whether it'd slow down the report, I can't see how that'd ever be the case