Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!uunet!munnari.oz.au!manuel!ccadfa!ghm
From: ghm@ccadfa.adfa.oz.au (Geoff Miller)
Newsgroups: comp.databases
Subject: Re: PICK dbms/os on UNIX
Message-ID: <2431@ccadfa.adfa.oz.au>
Date: 13 Jun 91 02:55:21 GMT
References: <1991Jun10.223018.26414@ringer.cs.utsa.edu> <10628@idunno.Princeton.EDU> <1991Jun11.224403.9172@ringer.cs.utsa.edu> <1991Jun12.034839.25161@PacBell.COM>
Organization: Computer Centre, University College, UNSW, ADFA, Canberra, Australia
Lines: 30

jmcarli@PacBell.COM (Jerry M. Carlin) writes:

>In article <1991Jun11.224403.9172@ringer.cs.utsa.edu> geckhard@ringer.cs.utsa.edu (Gary Eckhardt) writes:
[...stuff about translates from other files deleted...]
>>The database was approximately 80 Megabytes or so.  We were close to
>>filling up a 100 meg disk.  This inefficiency has been demonstrated
>>to be the same across two different platforms that I've seen it run
>>on. 

>A couple of things would cause this slowness. The basic cause is typically
>choosing a bad 'modulo'. All Pick files are hashed and if the size of the
>primary area is too small everything goes into a doubly-linked list and
>this can cause horrendous slowness. The other cause of slow restore times
>is resetting the 'modulo' which causes a lot of recalculation.

>Actually the primary performance problem I used to have was lack of
>secondary indicies which caused a long delay for each retrieval. I 
>believe this is now fixed.

Prime "Information" (Pick as a software package rather than an OS) now has
what Prime call a "dynamic" file structure, in which choice of modulo and
resizing are basically automatic.  This works very well for us.  Also,
Prime offer a facility to create alternate key indexes, which can be
on calculated values or the individual values of multivalued fields.  Such
indexes are updated automatically.  Given that these things have been
done, I wonder when they will be (or if they are already) available in 
other implementations of Pick under Un*x.

Geoff Miller  (ghm@cc.adfa.oz.au)
Computer Centre, Australian Defence Force Academy