alt Hacker NewsI don't think it really matters in terms of their question though, given MySql on the same specs doesn't have the problem and postgres does. Quite clearly it has something to do with indexes and what is the wall postgres is running into that causes the drop off on quite low amounts of rows. If the answer is just get more RAM, it kind of implies postgres is not really that scalable. Especially if the drop off is proportional to the number of rows.
Why are you using hash indexes? They're much less widely used than standard B-Tree indexes. The bucket split code likely isn't very scalable [1].
I suggest testing the same workload with your existing hash indexes replaced with equivalent B-Trees.
[1] https://github.com/postgres/postgres/blob/master/src/backend...