BDR Consistency in Insert/Update pkey conflicts - Mailing list pgsql-hackers

From Robert Berry
Subject BDR Consistency in Insert/Update pkey conflicts
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Msg-id CAM=RetHq3fsfvpTms0HH_RM4GS7hT-K3Qrof1JpeyT2rqyr97Q@mail.gmail.com
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I'm curious to know what the expected behavior is for an insert / update conflict on a primary key field.  

The wiki suggested "divergence conflicts" would be logged and replication would halt for the downstream master.  There is a case where the databases "diverge" such that they are no longer consistent, and where no error is logged and replication continues.  

The test case is summarized as inserting a record on a first node with pkey='x'.  After this record propagates, then insert a record with a different node with pkey='y', and at the same time update the first node's record to change the key to 'y'.  Depending on timing, the result is that the first node will only have a single record, while the other nodes will have an x and y record.


Is this considered a divergence conflict and what is the expected behavior for this case?  

Also is there is a published list of conditions where masters can become inconsistent and that is expected behavior -- or should that never happen?

Best Regards,
Robert


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