On Fri, Aug 12, 2011 at 12:23 PM, Heikki Linnakangas < heikki.linnakan...@enterprisedb.com> wrote:
> I think it would also be fairly simple to decrease levelstep and/or adjust > buffersize on-the-fly. The trick would be in figuring out the heuristics on > when to do that. > I would be simple to decrease levelstep to the it's divider. It seems quite hard to dicrease it, for example, from 3 to 2. Also, it's pretty hard to detect that sub-tree actually doen't fit to the cache. I don't see much difficulties in buffersize runtime tuning. > Another thing occurred to me while looking at the buffer emptying process: > At the moment, we stop emptying after we've flushed 1/2 buffer size worth of > tuples. The point of that is to avoid overfilling a lower-level buffer, in > the case that the tuples we emptied all landed on the same lower-level > buffer. Wouldn't it be fairly simple to detect that case explicitly, and > stop the emptying process only if one of the lower-level buffers really > fills up? That should be more efficient, as you would have "swap" between > different subtrees less often. Yes, it seems reasonable to me. ------ With best regards, Alexander Korotkov.
