Query Folding In Power Query

Reza Rad discusses the performance implications of query folding in M:

I can’t start talking about the issue without explaining what Query Folding is, so let’s start with that. Query Folding means translating Power Query (M) transformations into native query language of the data source (for example T-SQL). In other words; when you run Power Query script on top of a SQL Server database, query folding will translate the M script into T-SQL statements, and fetch the final results.

Click through for more details.  The advice here sounds pretty similar to what we get for optimizing Integration Services:  push as much of the heavy lifting onto well-optimized source queries as possible, particularly when it comes to filtering out rows.

Related Posts

Relationships In Power BI

Teo Lachev shows us the importance of defining relationships in Power BI: However, If there isn’t a direct relationship between ResellerSales and Employee, the moment you add an unsummarized field from the second table on the many side, such as Employee[FullName] after adding SalesTerritoryCountry and ResellerSales[SalesOrderNumber), you’ll get the error “Error: Can’t determine relationships between the […]

Read More

Calculating Future Revenue Streams With Phasing

Matt Allington walks us through a somewhat complicated scenario with income stream projections but inconsistent monthly payout rates: The first thing I decided to do was work out which was the first month of the policy.  I used LOOKUPVALUE to do this because the Calendar table was not connected to the policy table.  Instead of […]

Read More

Categories

November 2016
MTWTFSS
« Oct Dec »
 123456
78910111213
14151617181920
21222324252627
282930