In transform map I have a custom field and getting error while making it coalesce

[prasannah]

Hi Everyone,
in Transform map I have field called reference id which is custom field. and If i make it as coalesce and 

Create new record on empty coalesce fields -- true

 (check box true) then I am getting an error, what will happen if we click ok and click index and what is the impact of that? does this will create any new custom behavior? 

[Nehal Dhuri]

Hello @prasannah ,
It is best practice to index any field you are using to coalesce on. It will improve the performance of your transform process.

[Nehal Dhuri · Accepted solution]

You might find the following articles helpful: 

https://www.servicenow.com/community/developer-blog/servicenow-things-to-know-70-indexing-coalesce-f...

https://www.servicenow.com/community/developer-blog/improve-import-set-performance-with-the-coalesce...