>>>>> "MichaelDBA" == MichaelDBA <MichaelDBA@xxxxxxxxxxx> writes: MichaelDBA> Yep, you're right, Andrew, adding a couple rows made it do MichaelDBA> the index only scan. I reckon I got misled by turning off MichaelDBA> sequential scans, thinking that actual rows were not MichaelDBA> important anymore. Overly simplistic reasonings can get MichaelDBA> one into trouble, lol. We do some odd stuff with the statistics estimates for completely empty tables because (a) it's not common in practice for a table to be always empty (i.e. the emptiness is usually transient) and (b) if you take the emptiness of a table at face value, you end up generating insanely bad plans for certain FK check queries that may not get replanned quickly enough to mitigate the performance impact. -- Andrew (irc:RhodiumToad)
