Best practices for Custom entities used to summarize data for a report

Hi,

I was trying to build a CRM Online FetchXML report fetching more than a million records (the SQL equivalent had several JOINS, cases, nested SELECT and etc.), so I've resorted to create a custom entity that will store the data for each row of the original report.

So I want to ask you, what best practices do you know for this approach ?

I plan to build the custom entity then add a plug-in on the Update event of the main entity of the report (so that when the main entity is updated a record is created in the Custom entity table). 

I will check all the link-entities in the plug-in and summarize the data there, but I think I might be missing something.

Thanks.

Best regards,

Evgeni Dyulgerov