Hi, On 2020-03-21 23:53:05 -0500, Justin Pryzby wrote: > On Sat, Mar 21, 2020 at 07:33:02PM -0700, Andres Freund wrote: > > While your recent btree work ensures that we get the heap tids for an > > equality lookup in heap order (right?), > > I think when I tested the TID tiebreaker patch, it didn't help for our case, > which is for inequality: (timestamptz >= start AND timestamptz < end). > > That seems to explain why, although I don't understand why it wouldn't also > apply to inequality comparison ?
Because tids are only ordered for a single lookup key. So if you scan across multiple values you could have key:page visited in the order of 1:1 1:2 1:99 2:1 2:7 99:1 or such, i.e. the heap pages would not be monotonically increasing. You can't however have 1:17 1:1, because for a specific key value, the tid is used as an additional comparison value. Greetings, Andres Freund
