One of the purposes of entity.get() is to detect MultipleObjectsFoundError. If you add limit 2 to SQL queries, SQL server can use less resources while executing the query. For example, SQL server can stop populating internal cache if only two records needed. Yes I know that we may use cursors, but still sure that limit 2 will not hurt in performance in any way.
Agreed, should be fixed
Fixed #83: Entity.get() should issue LIMIT 2 when non-unique criteria…
… used for search
Now Pony adds LIMIT 2 when it thinks that a query can return more than one row. But when Pony sees that the query uses an unique key and thus no duplicates are possible, then LIMIT 2 will not be added, because it looks redundant and shouldn't influence anything.