Avoid 'canceling statement due to conflict with recovery'

When graph-node uses a shard with read replicas, replication conflicts can lead to an error canceling statement due to conflict with recovery. With that error, it is generally ok to retry the query, possibly with some backoff. The retry logic should guard against queries though that take so long that they are virtually guaranteed to fail with that error. For example, a query that would take 2 minutes will almost certainly fail if the underlying deployment has a decent amount of updates.

One way to avoid this would be to retry the query not against the same replica, but against the main database, where this error cannot happen.

Traccia il percorso della query e dei retry della replica di lettura dello shard di graph-node, quindi esamina come vengono gestiti gli errori di PostgreSQL dovuti a conflitti di recovery. Confronta il retry su un'altra replica con l'instradamento della query al database principale, tenendo conto delle query di lunga durata; il lavoro è completato quando il conflitto può essere ritentato senza inviare ripetutamente query inadatte a una replica.