Why are calculated fields not syncable in Heroku Connect?

Issue

You're creating or updating a mapping in Heroku Connect. When you map a field you see a message saying "Calculated fields are not syncable: ".

Resolution

Calculated fields (also known as, Formula fields and Roll-up fields) do not always update the Salesforce system fields that Connect uses to synchronize these fields (SystemModstamp, LastModifiedAt). This means that while an initial load may successfully "synchronize" the data, the data may not stay synchronized after an initial load.

Further information:

• https://devcenter.heroku.com/articles/heroku-connect-diagnose#check-calculated-fields
• https://devcenter.heroku.com/articles/heroku-connect-database-tables#cross-object-formula-and-roll-up-summary-fields