OK. I'm gonna make a couple of guesses here:
1: clinicaldocuments.patientidentifier is an int8 and you're running
7.4 or before.
-- nope int4 and 8.1
2: There are more rows with clinicaldocuments.patientidentifier= 123
than with documentversions.documentstatus = 'AC'.
-- nope generally speaking all statuses are 'AC'
3: documentversions.documentidentifier and
clinicaldocuments.dssdocumentidentifier are not the same type.
-- nope both int4
Any of those things true?