Re: Object databases beat joins (was: Re: ODMG Website?)

"Bob Badour" <bbadour_at_golden.net> wrote in message news:RfVwa.58$oC4.13359172_at_mantis.golden.net...
> Clustering will further reduce the single random IO to zero.

I'm skeptical about clustering idea. Physical locality is a goal that is difficult to achieve. When implemented it is so complex that requires extraordinary DBA effort to maintain it. I was never convinced that mastering Oracle Clusters, for example, is worth the effort.

In general, we can't be certain how many layers of indirection is between the data stored on disk and query output. We might think that blocks x and y are collocated, but filer has striping. Also, storing records with the same join key value in the same block migh be good for that particular join order, but may adversely affect other queries. Then, query optimization is so overwhelmed with problems that it simply couldn't devote sufficient attention to developing a convincing cost estimation model in the clustering case. Finally, clustering is only important for sequential-read devices (aka disks), and would progressively become less relevant as soon as random-access persistent storage (solid state disks, etc) become more common. Received on Fri May 16 2003 - 01:30:01 CEST