On 2018-08-22 20:48:48 +0200, Pierre Ducroquet wrote: > On Wednesday, August 22, 2018 6:51:55 PM CEST Andres Freund wrote: > > On 2018-08-22 18:39:18 +0200, Andreas Joseph Krogh wrote: > > > Just to be clear; The query really runs slower (wall-clock time), it's not > > > just the timing. > > > > I bet it's not actually running slower, it "just" takes longer to start > > up due to the JITing in each worker. I suspect what we should do is to > > multiple the cost limits by the number of workers, to model that. But > > without the fixed instrumentation that's harder to see... > > It depends on the query. It has been shown in other threads that query can > indeed take longer to run because of JITing : if the cost is too low to fire > LLVM optimizer, the generated code can be so bad it will be slower than the > non-JIT executor.
This largely seems to be orthogonal to what I'm talking about. > Cf for instance a previous discussion here : > http://www.postgresql-archive.org/PATCH-LLVM-tuple-deforming-improvements-td6029385.html I'd wish people stopped using www.postgresql-archive.org. It's *NOT* postgresql.org maintained, in fact I do not know who does. It does shows ads when downloading links, which I'm personally not ok with. Greetings, Andres Freund
