Re: OO fans bashing Joins

Ruud en Maud wrote:

> Going through the Btree will only mean one or two disk (or
> preferably cache) reads. Doesn't take that much time. With modern
> hardware it is not on a timescale you and I can observe.

you're right .. but navigating in the same process's memory is even cheaper than that
(no disk read's at all - nor consulting the database process)

> You seem to suggest that an RDBMS will always get its data from
> disk. This is only partly true, since most RDBMSs will use some sort of
> cache. That makes it a lot faster to retrieve data from the RDBMS. I
> wonder what the comparison to an ODBMS will be then...

again you're right .. there usually IS a cache ... but it's a bit tough to rewrite
10 database books in a news thread - there are some things which you expect people to know ...

> Question: Is it likely that hundreds of related objects fit on a
> single page? This seems to imply that either the objects should be very
> small or the pages very big.

Typical pages have 4K or something - again - you are right .. but often objects are very
fine grained - sometimes they are not ... this really depends totally on your app and how you configure
your system ... and YES there's a tradeoff between page size and fetch speed and all this ..
As I said above .. it's tough to write the book of database theory in a news discussion :-)

>
> Very interested in a reaction, especially on the question.
>

Hope that answers the questions. No unexpected answers and no wonders I presume :-) and no new
results on how to beat the laws of physics :-) Sorry :-)

Cheers

Wolfgang

--
================================================================
EMail: wk_at_objectarchitects.de
Web:   http://www.objectarchitects.de/ObjectArchitects/