- From: Kendall Clark <kendall@monkeyfist.com>
- Date: Wed, 18 Jan 2006 13:58:47 -0500
- To: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
- Cc: dawg mailing list <public-rdf-dawg@w3.org>
On Jan 18, 2006, at 12:18 PM, Steve Harris wrote: >> Actually, now that I think about it, that's not *entirely* true. Real >> (as opposed to toy) database cost models include table size, and even >> for arbitrary 3rd party graphs, with clever caching and use of HTTP, >> a SPARQL query analyzer could make some good guesses (so, imagine the >> ideal case: all the graphs are cached locally and known to be fresh), >> so it's not as bad as I made it seem. > > It's not even that easy, without running the main part of the query > for > real it's not possibly to calculate how much effort will be > required to > satisfy the OPTIONAL blocks or how many UNION branches you will > have to > take. My estimation code assumes worst-ish cases for those, which > is often > not accurate. Absolutely! My point was just in re: assembling RDF datasets. That's only part of a cost model for query analysis, as you point out. :> >> But in the common or pathological cases (where all graphs are >> unknown, uncached, and have to be retrieved from arbitrary origin >> servers), well... -shudder-. > > Quite. It's ugly, yes -- but better ugly than impossible, I think. Cheers, Kendall
Received on Wednesday, 18 January 2006 18:58:58 UTC