QUESTION:
What causes this error in DupeBlocker?
Note: this error can also occur for Leads and Accounts; e.g. ***Trigger: Lead before delete, ***Trigger: Account before delete
*** Trigger: Contact before delete
*** isMerge value: false
*** Trigger.new size: 0
*** Trigger.old size: 1
*** Exception Type: System.DmlException
*** Exception Cause: null
*** Exception Message: Delete failed. First exception on row 0 with id a0t000000008mKyAAI; first error: ENTITY_IS_DELETED, entity is deleted
*** DML Row-level Errors:
DML Status Code: system.StatusCode.ENTITY_IS_DELETED
Original DML Row Index: 0
DML Fields:
DML Error Message: entity is deleted
ANSWER:
This error typically occurs during the initial phase of a DupeBlocker key rebuild as all of the existing keys are being deleted. The record keys need an "update" but are deleted before the update executes. This error can be ignored as the key for the record(s) in question should be rebuilt by the key building process.