Re: SHOULD use POST for expensive queries?

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