On Mon, 2008-01-21 at 21:52 +0200, Alex Mizrahi wrote: > IE> Part of the problem with Elephant is that we currently create CLOS > IE> objects in memory for every 'row' that is touched in a query (or > IE> touched during an index operation). We have to de-serialize the > IE> record, create an object, initialize any transient slots, etc. The > IE> SQL engine, by contrast, can just keep track of a list of OIDs and > IE> then count the size of the arrays that result from any joins. This is > IE> a much cheaper set of operations per-row (i.e. per object). If we > IE> only read OIDs into memory until the final step when we need to access > IE> a slot, we can save quite a bit of the cost of object creation. > > also backends which connect to database via a socket have considerable > communication overhead, i think it's even larger than deserialization > impact. > > IE> My hope is that a query system would implement this model properly. > IE> Unfortunately, this will not happen soon, as much as I'm itching to do > IE> it! > > OTOH it's fairly easy to make function that counts total number of entries > in btree or in some range, at least it's easy with db-postmodern -- it just > translates to COUNT(*) query. > if there is such a big demand for this feature, we can just implement it as > backend-specific advantage ^__^.
I'm not sure how many people desire such a function, but I think it is certainly useful and something I want to leverage. I seems only BDB would not support this... Joubert _______________________________________________ elephant-devel site list elephant-devel@common-lisp.net http://common-lisp.net/mailman/listinfo/elephant-devel
