Peter Eisentraut <peter.eisentr...@2ndquadrant.com> writes: > On 2019-08-26 13:28, Daniel Migowski wrote: >> I would like to implement a fallback solution >> that detects such errors and automatically updates the nextvalue of the >> sequence when the nextvalue is already used on insert.
> ISTM that such a system would likely have many of the same problems as > the often-proposed ignore-errors mode for COPY, namely that you can't > catch errors and do something else other than rethrowing the error. In principle you could probably use the same infrastructure used by ON CONFLICT to detect the unique-key violation. But ON CONFLICT is mighty complicated, and not very cheap either. I don't for one second believe Daniel's assertion that this could be done without a significant COPY performance hit. I'm also dubious that the right response to a duplicate key would be as simple as "try the next nextval() result". I for one wouldn't be satisfied with waiting for COPY to grind through a few thousand/million sequential nextval values before finding one that doesn't conflict with the existing table entries. The actually-sound advice for loading data that might have conflicting serial values is to do the equivalent of setval('sequence', max(existing keys) + 1) before you start loading. I wonder whether there's a way to make that simpler. regards, tom lane