🚀 go-pugleaf

In article <164@ima.UUCP>, johnl@ima.UUCP (John R. Levine) writes:
> Both left and right hand key compression are useful ways to cram more entries
> into a tree node, and there's no argument that in the usual case that it's
> more expensive to fetch a node from the disk than to process it once it's read
> in, they're a big win.  On the other hand, I have this blindingly fast Eagle
> disk drive lashed up to a very sluggish IBM PC, and the tradeoffs are not
> always what you'd assume.

	Actually, I have talked to a couple of different relational
database companies, and their studies indicate that key compression is
not a win. The reason for this is that yes, a disk access is normally
longer than the time necessary to uncompress, but since most of the
bigger systems try to cache the indices, there may not be a disk
access. Then the compression is a straight loss. Of course, compression
would mean you can get more index into the cache, but their studies
seem to argue that compression just does not speed up access time.


-- 

					eric
					...!seismo!umcp-cs!aplcen!osiris!eric