Re: optimizer_index_caching and optimizer_index_cost_adj deprecated by system stats?

From: Mladen Gogala <mgogala_at_yahoo.com>
Date: 14 Mar 2008 08:35:56 GMT
Message-ID: <47da38ec$0$1349$834e42db@reader.greatnowhere.com>

On Thu, 13 Mar 2008 13:44:50 -0700, Mark D Powell wrote:

> I am against modifying the parameters away from the defaults on any
> release. Jonathan has written about some of the side effects that are
> possible when you do change the parameters.

I have no compunction about modifying the optimizer_index_caching because this parameter does supply realistic information which doesn't have a smart default. I usually do not set optimizer_index_cost_adj as this information can be manipulated through system statistics, if needed. Optimizer has no other way to figure the portion of index that is cached and you provide a default that is much "truthier" (sorry Mr. Colbert, I just had to use your word) then the default which says that index is not cached at all. I find this particular parameter useful in OLTP environments.

-- 
Mladen Gogala
http://mgogala.freehostia.com

Received on Fri Mar 14 2008 - 03:35:56 CDT

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