Posts in Category ‘M’

Tidy up Power BI models with the Power BI Cleaner tool

Edit 23th June 2020: Updated version (see download link at the end of the article) to reflect changes with the vpax fileformat in DAX Studio versions V11.0 upwards.

The VertiPaq-Analyzer tool is one of the great community tools that I really cannot live without. It gives me a great overview of all elements in my model and identifies potential performance problems by showing the storage requirements of each column. So when seeing expensive columns, the first question that arises is: “Do I really need this column or could I delete it?”. Luckily, this can now be answered with my new Power BI Cleaner tool. This tool shows the usage of all columns (and measures) within the tables of the VertiPaq Analyzer.

Power BI Cleaner shows unused columns in the VertiPaq-tables

Power BI Cleaner tool

So whenever there is no entry in the column “Where Used” you can go ahead and eliminate the column (or measure) from the model. Well – with one exception actually: Fields used in the definition of incremental load policies are currently not identified. So make sure to consider this before running wild 😉 Read more

Advanced transformations on multiple columns at once in Power BI and Power Query

You can apply simple transformations to multiple columns at once in Power Query using the UI only. In this article I show how you can apply advanced transformations on multiple columns at once instead. You can also use this to use custom functions instead. And lastly for the lazyefficient fans of custom M-functions: You will get a new “TranformAllMyColumnsAtOnceHowILikeIt”-function as well 😉

Background

The Transform-tab in the query editor is sensitive to the columns you select. So if you select multiple number columns for example, some number transformations will be greyed out and are therefore not accessible:

Some symbols are greyed out, Advanced transformations on multiple columns at once in Power BI and Power Query, Power BI, Power Query, Power BI Desktop

Some symbols are greyed out

So how could I then multiply all my columns by 10 for example, as the symbol for multiplication is greyed out? Read more

Dynamically create types from text with Type.FromText in Power Query and Power BI

In this article I’ll show you how to create types from text in Power Query, enabling you to dynamically change types via functions for example. It’ll come out as a custom Type.FromText function which has been asked for in the comments of this article: https://www.thebiccountant.com/2017/01/09/dynamic-bulk-type-transformation-in-power-query-power-bi-and-m.

Problem

To transform a column to type text can be done like so:

Table.TransformColumnTypes(Source,{{"Column1", type text}})

This transforms the “Column1” from table “Source” to type text.  Now, if you want to make the type dynamic and move it to a function parameter like so:

(VariableType as type) =>

Table.TransformColumnTypes(Source,{{"Column1", VariableType}})

This returns a function dialogue as follows:

Read more

Performance tip for aggregations after joins in Power Query and Power BI

This article was edited on 2nd Nov 2019. JoinKind.Local has been removed to avoid problems with merges on tables with primary keys:

In this article you’ll learn how to speed up the aggregation of joined/merged tables by orders of magnitude (I recorded up to 30 times faster execution times). This method works for merges where both table have multiple rows for each keys. If one of your tables has a primary key, the method Chris Webb describes here works just as good: Chris Webb’s article on how to improve performance on aggregations after joins using primary keys .

You can follow along the different methods in this file:  PerformanceAggregationsAfterMerges1_Upload.zip

Background

When you join a table to another table in Power Query, the UI gives you the option to either expand the columns (default) or aggregate the contents of the joint tables. That’s useful if multiple rows are returned for the rows of the table that has been joined to (left table):

Read more

Parent-Child Hierarchies with multiple parents in Power BI with Power Query

I’ve written about a method to dynamically flatten parent-child-hierarchies also with multiple parents some while ago here. I’ve actually used this approach for Bill-of-materials cases and refined that approach in a series starting here. There, the quantities are aggregated in M already, as they are not supposed to change. But if one wants to use the hierarchical structure to report on transaction tables where several filters shall be applied, one has to adjust the data model a bit:

DimNodes

If you have parent-child-hierarchy with multiple parents, my function will a table like below, where the children with multiple parents still reside in different rows:

Read more

Power BI administration made easy with Power BI REST API custom connector

Today I read the (as always) great article by Matthew Roche “Governing Power BI just got a little easier” and couldn’t find a description on how to get to this promising window with all the admin goodness. So here it comes how to build your Power BI REST API custom connector then 😉 :

Create a custom connector for the Power BI REST API

Miguel Escobar has done a fantastic job to make it super-easy for you here.

Edit 30th September 2019: This repo has just been updated and includes a version with API secret. So if you’ve downloaded that content before and got an authorization error, please get the new files.

Get data from your connector

After you’ve stored the .mez-file in the correct folder (C:\Users\<YourUserNameGoesHere>\Documents\Power BI Desktop\Custom Connectors) and open Power BI Desktop again, you will be greeted with this warning message: Read more