On Mon, 8 Sep 2003, Neil Conway wrote:

> On Mon, 2003-09-08 at 11:56, scott.marlowe wrote:
> > Basically, Postgresql uses an MVCC locking system that makes massively 
> > parallel operation possible, but costs in certain areas, and one of those 
> > areas is aggregate performance over large sets.  MVCC makes it very hard 
> > to optimize all but the simplest of aggregates, and even those 
> > optimzations which are possible would wind up being quite ugly at the 
> > parser level.
> As was pointed out in a thread a couple days ago, MIN/MAX() optimization
> has absolutely nothing to do with MVCC. It does, however, make
> optimizing COUNT() more difficult.

Not exactly.  While max(id) is easily optimized by query replacement, 
more complex aggregates will still have perfomance issues that would not 
be present in a row locking database.  i.e. max((field1/field2)*field3) is 
still going to cost more to process, isn't it?

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