Re: Hints in Practice

From: Robert Klemme <shortcutter_at_googlemail.com>
Date: Wed, 23 Aug 2006 23:05:10 +0200
Message-ID: <4l3u87F5edsU1@individual.net>

Bob Jones wrote:
> "Robert Klemme" <shortcutter_at_googlemail.com> wrote in message

>> http://publib.boulder.ibm.com/infocenter/dzichelp/v2r2/index.jsp?topic=/com.ibm.db2.doc.admin/bjndmstr663.htm
>>
>> You see, it seems not to uncommon to have hints as a DB feature.
>>

>
> Good links. I have worked with DB2 for years and have never even heard of
> those hints. In fact, I have never seen a single line of code with hints.

If you look at those pages you might discover that those hints are very much different from SQL Server and Oracle hints: hinting in DB2 seems to be restricted to manipulating statistics...

> The use of hints is discouraged. If you go to one of those DB2 classes, they
> will tell you the same.

That's basically what I stated in the first posting and asked for verification.

> I am not sure about SQL Server. Will they encourage the use of hints? I
> doubt.

I think, nobody really does. The only statement of you that attracted some fire was that about missing confidence. I rather see providing hints as a manifestation of realism: a modern DB engine has reached a level of complexity that it's realistic to assume that there are corner cases where automatic optimization does not yield optimal results; and the product has reached such a wide distribution that it's likely that someone stumbles into them. And so there is an additional handle for knowledgeable users to tweak. It's similar as with automatic transmission: most of the time you just drive in D but sometimes you need to manually shift gears - and you can do that with all automatic transmissions out there.

Cheers

robert Received on Wed Aug 23 2006 - 16:05:10 CDT