I was performing some data masking on a few fields in the Account object and saw that about 150 records could not be masked due to duplicate values in a field that had an index and was marked as an external. How is that possible? I did not mask that field and that data is like that in production. Is there any way Salesforce would allow records to be indexed/marked as external to have duplicate values?

1 Answer 1


Fields marked as an external id don't need to always be unique. Uniqueness is a separate constraint, and it is not selected by default.

So you got records with duplicate values because some process (or perhaps more likely, somebody) duplicated a value for that external id, and the field definition did not restrict that.

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