well, yes, you are right that exception does abort the transaction. but even if you use something like 'on conflict do nothing' to avoid the exception, you stil

well, yes, you are right that exception does abort the transaction. but even if you use something like 'on conflict do nothing' to avoid the exception, you still can get problems with concurrent writes (see my sibling comment https://news.ycombinator.com/item?id=41169638 https://news.ycombinator.com/item?id=41169638) REPEATABLE READ or SERIALIZABLE isolation levels would help with that, as the name suggest repeatable read ensures that the read made by inserts constraint check is repeatable in successive select (or update) statements. https://www.postgresql.org/docs/current/transaction-iso.html https://www.postgresql.org/docs/current/transaction-iso.html is pretty comprehensive.