Avoid exploding number of rows when joining tables

[riku_okawa]

When using the Join tool in Alteryx to join tables, the number of rows may explode. This can be very time consuming to calculate, so is it possible to warn the user before execution?
For example, in python we can use the validate option in pd.merge to throw an error when you don't expect an exploding join, but I'm looking for a similar feature in Alteryx.

[danilang · Accepted solution]

Hi @riku_okawa 

There isn't a built in feature that you can use, but you can certainly build one into the workflow

In the top container, count the number of records grouped by the join fields in each input.  Join the results and get the grand total.  The message box before the browse stops the workflow by throwing an error if there will be more than X records.  Make sure that you have "Cancel Running Workflow on Error" set in the Workflow->Runtime properties

The tools in the Synchronize container are there to ensure that the "Total after Join" container completes before the actual join is started. 

Dan