Tom Lane wrote:
=?utf-8?Q?=E5=B0=8F=E6=B3=A2_=E9=A1=BE?= <guxiaobo1982@xxxxxxxxxxx> writes:
[ snip a lot of marketing for SQL Server ]
I think the part of this you need to pay attention to is
Of course, nothing is entirely free, and this reduction in space and
time come at the expense of using CPU cycles.
We already have the portions of this behavior that seem to me to be
likely to be worthwhile (such as NULL elimination and compression of
large field values). Shaving a couple bytes from a bigint doesn't
strike me as interesting.
Think about it on a fact table for a warehouse. A few bytes per bigint
multiplied by several billions/trillions of bigints (not an exaggeration
in a DW) and you're talking some significant storage saving on the main
storage hog in a DW. Not to mention the performance _improvements_ you
can get, even with some CPU overhead for dynamic decompression, if the
planner/optimiser understands how to work with the compression index/map
to perform things like range/partition elimination etc. Admittedly this
depends heavily on the storage mechanics and optimisation techniques of
the DB, but there is value to be had there ... IBM is seeing typical
storage savings in the 40-60% range, mostly based on boring,
bog-standard int, char and varchar data.
The IDUG (so DB2 users themselves, not IBM's marketing) had a
competition to see what was happening in the real world, take a look if
interested: http://www.idug.org/wps/portal/idug/compressionchallenge
Other big benefits come with XML ... but that is even more dependent on
the starting point. Oracle and SQL Server will see big benefits in
compression with this, because their XML technology is so
mind-bogglingly broken in the first place.
So there's certainly utility in this kind of feature ... but whether it
rates above some of the other great stuff in the PostgreSQL pipeline is
questionable.
Ciao
Fuzzy
:-)
------------------------------------------------
Dazed and confused about technology for 20 years
http://fuzzydata.wordpress.com/
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