> But compressing compressed data will in many cases turn out
> bigger. This is, as far as I have understood it, strictly
> opposed to the intension which was to minimize the number
> of pages used to store the data.

With smart algorithms the size difference is generally not
very significant. The primary cost comes with the time it
takes to perform the compression. If there is no size
benefit to offset the cost of processing then the time it
takes is a total loss.

If the time lost in trying to compress uncompressable data
is significant then we will definitely need compression to
be configurable. If the time lost is not significant then
we can leave it on and ignore it - making it transparent
which is the desireable goal.

There is also a cost/benefit analysis to be done according
to the size of the compressed data. If the data would fit
into a normal blob storage block anyway, then there is no
benefit in compression - except perhaps in transport to the
client. In applications with mostly small blobs (I have
many of those) then compression may not be desirable.

--
Geoff Worboys
Telesis Computing