PG Bug reporting form <noreply@postgresql.org> writes:
> We saw a corruption in 3 different environments in one of the unique indexes
> (named “npn”) in “files” table.
> It seems as if not all the rows (that should be part of this index) in the
> table are indexed, and therefore “duplicated” rows (rows that violates the
> index constraint) are allowed to be inserted to DB.
Are any of the indexed columns of string types (text, varchar, etc)?
And have you upgraded the underlying OS since creating the index?
If so, you've likely been bit by locale changes. See
https://wiki.postgresql.org/wiki/Locale_data_changes
regards, tom lane