With a postgres writer it appears that if Bulk Insert is set to Yes, if you attempt to write a string value of NULL to a varchar column that has a Not Null constraint it is interpreted as a genuine null and results in a fatal error
Error was 'ERROR: null value in column "value" violates not-null constraint
If Bulk Insert is set to No, the value is written as a string as expected
Is this a known issue? This is in FME(R) 2021.2.6.0 (20220727 - Build 21821) so may have already been addressed.