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:
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):
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:
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:
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
When you’re dealing with a beast like DAX you can use any help there is, right? So here I show you how you can debug DAX variables who contain tables or show the result of multiple variables at once. So you can easily compare them with each other to spot the reason for problems fast.
Please note, that currently only comma separated DAX code is supported.
Watch this measure from Gerhard Brueckl’s brilliant solution for dynamic TopN clustering with others. It contains 5 variables who return tables and one variable with a scalar:
Measure with variables who contain tables and scalars
If you want to follow along how this calculation is evolving for each value in a matrix, my VarDebugMeasure will show details of every variable like so:
Measure to debug DAX variables
CALCULATE is the most powerful function in DAX, as it allows you to change the filter context under which its expression is evaluated to your hearts content. But with big number of options to choose from, often comes big frustration when the results don’t match expectations. Often this is because your syntax to modify the filter context doesn’t do what you’ve intended. Unfortunately CALCULATE only displays its result and not how it achieved it, so debugging becomes a challenge. This is where my CALCULATE Debugger measure can help out:
DAX CALCULATE Debugger
This is a measure that returns a text-value, showing the number of rows of the adjusted filter context table, the MIN and MAX value of the selected column as well as up to the first 10 values. Just place this measure beneath the CALCULATE-measure in question and try to find the error 😉
In a previous post I introduced the concept of a function that searches for an occurrence of a character or string within all columns of a table. Here I share the full “Table.ContainsAnywhere” – function with parameters for many useful options.
Function parameters and options
- The first parameter “MyTable” refers to the table to search through
- The 2nd parameter “MySearchStrings” can be either a text field or a list of strings to be searched for. The function will take care of any of these cases automatically.
- If the 2nd parameter is a list and this 3rd parameter is null or not speified, the function will return true if any of the list items is found within the table. But if set to “All”, all list items have to be found somewhere in the table for the function to return true.
- By default, the search will be made in a case sensitive mode (as this is the default-mode in Power Query). But any entry into the 4th function parameter will turn this to a case insensitive mode instead.
- By default, the string or list entry has to match fully with any entry in the table. Again, any entry in the 5th parameter swaps that to a partial match.