On Mon, Nov 14, 2016 at 2:35 AM, Alvaro Herrera <alvhe...@2ndquadrant.com> wrote:
> Magnus Hagander wrote: > > > But then consider the same table. Except rows are typically updated once > or > > twice when they are new, and *then* go read only. And we also have a > > process that at some point deletes *some* old rows (but not all - in > fact, > > only a small portion). > > > > In this case, the next INSERT once VACUUM has run is likely to stick a > > "new" row somewhere very "far back" in the table, since there is now free > > space there. This more or less completely ruins the BRIN index usability, > > as the "old" blocks will now contain a single row from a "new" series. > > Yeah. When we initially discussed BRIN, there was a mention of allowing > a BRIN index to guide new tuple location -- something like > auto-clustering, if you will. We haven't discussed the exact details > but I think something along those lines is worth considering. > What I'm talking about is something that would be a lot simpler than auto-clustering. I'm not even talking about trying to detect if the row was about to go into the right place -- this might be expensive and certainly more complicated. I'm only talking about a simple case where we *never* put anything anywhere other than at the end of the table, period. That should make the check both cheap and simple. -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
