On Fri, Apr 17, 2015 at 5:24 AM, Albe Laurenz <laurenz.a...@wien.gv.at> wrote:
> >> Even with COW, I can see fillfactor < 100% still have its virtues. For > >> example, HOT update can avoid adding an extra index item on the index > >> page if it finds the new item can be inserted in the same heap page. > > > That's true, the new physical location on disk is transparent to the > DBMS so it has no more or less > > housekeeping with or without COW, but the housekeeping still has to be > done somewhere, so it helps to > > understand which is more efficient. I'll see if I can produce some > empirical data unless anyone thinks > > it's a waste of time. > > I am quite certain that fillfactor < 100% will be a win even then (for the > right load). > Upating one (heap) block should always be cheaper than updating one heap > block > as well as (at least) one index block per index involved. Your last three words. I was ignoring the obvious (and likely) scenario of when more than one index needs to be updated. fillfactor<100% with COW still gets the win. Thanks! Geoff
