Re: Compression and on-disk sorting - Mailing list pgsql-hackers

From Zeugswetter Andreas DCP SD
Subject Re: Compression and on-disk sorting
Date
Msg-id E1539E0ED7043848906A8FF995BDA57901054657@m0143.s-mxs.net
Whole thread Raw
In response to Compression and on-disk sorting  ("Jim C. Nasby" <jnasby@pervasive.com>)
Responses Re: Compression and on-disk sorting  ("Jim C. Nasby" <jnasby@pervasive.com>)
List pgsql-hackers
> 1) Use n sort areas for n tapes making everything purely sequential
access.

Some time ago testing I did has shown, that iff the IO block size is
large enough
(256k) it does not really matter that much if the blocks are at random
locations.
I think that is still true for current model disks.

So unless we parallelize, it is imho sufficient to see to it that we
write
(and read) large enough blocks with single calls. This also has no
problem in
highly concurrent scenarios, where you do not have enough spindles.

Andreas


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