Path: utzoo!utgpu!cunews!cognos!nigelc
From: nigelc@cognos.UUCP (Nigel Campbell)
Newsgroups: comp.databases
Subject: Re: how bad is oracle? (really: query optimizers)
Message-ID: <9385@cognos.UUCP>
Date: 1 Mar 91 17:42:04 GMT
References: <1991Feb3.182558.14411@oracle.com> <70683@microsoft.UUCP> <13512@blia.sharebase.com> <1991Feb19.204354.16211@informix.com> <13594@blia.sharebase.com>
Reply-To: nigelc@cognos.UUCP (Nigel Campbell)
Organization: Cognos Inc., Ottawa, Canada
Lines: 36

In article <13594@blia.sharebase.com> mike@sharebase.com (Mike Ubell) writes:
>In article <1991Feb19.204354.16211@informix.com> barrym@informix.com (Barry Mednick) writes:
>>In article <13512@blia.sharebase.com> mike@woodstock.UUCP (Mike Ubell) writes:
>>>
>>>True enough, but: A good DBMS should beable to optimize at compile time
>>>and find the best query plan without help from the user and then store
>>>the plan so that time critical applications have acceptible performance.
>>Without help from the user, yes.  At compile time, perhaps not.
>>Consider what could change between compile time and run time:
>>  Indexes can be dropped and created
>>  The sizes of tables can change

[stuff deleted]

>
>(Gee I hate to keep plugging our features...)
>ShareBase III automaticly marks a query for recompile when indices
>are changed on any table in the query and the query is recompiled
>the next time it is run.  (In fact you can drop and recreate a

Dg/Sql will recompile and update the compile unit however at least for
rev 4 if it was a read only transaction that used the unit the compilation
was done in your local cache and the database was not updated with the
reopt code . What does Sharebase do in the situation . Dg/Sql Dba tools
allow you to issue an update command to recompile the units marked dirty
which can be part of jobs known to cause the stats to be skewed .
Dg also has the handy feature of letting you setting the row count on a 
table .



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Nigel Campbell          Voice: (613) 783-6828                P.O. Box 9707
Cognos Incorporated       FAX: (613) 738-0002                3755 Riverside Dr.
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