Re: A new proof of the superiority of set oriented approaches: numerical/time serie linear interpolation

"Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message news:463c813c$0$4036$9a566e8b_at_news.aliant.net...
> David Cressey wrote:
>
> > "Brian Selzer" <brian_at_selzer-software.com> wrote in message
> > news:8kY_h.7025$2v1.1573_at_newssvr14.news.prodigy.net...

> What can one say? Selzer's rant speaks to a shitty optimizer. It
> condemns a specific un-named product and nothing else.

> I have done lots of optimization. I have never achieved a gain from
> using a cursor, and I have achieved numerous huge big-O improvements by
> getting rid of cursors. Like taking an O(n^5) cursor algorithm and
> replacing it with a single select statement involving multiple joins,
> quantification and correlated subqueries that executed in O(n) -- and
> that was using a small footprint embedded dbms one could buy for a
> couple hundred dollars.
>
> Within a few moments of inheriting the cursor based code mentioned
> above, I recognized the cursor solution would not scale and I changed
> it. My boss was suitably impressed when he asked me to look into a
> performance problem found in the field, and I replied that I had already
> found it and fixed it.

Thanks Bob. The above comments put things back into perspective. Especially the point about big-O. I'll admit that my experience was not mainly about dealing with preformance issues as such, except for one or two contracts. In general, the rule about design and development was:

Use simple and sound design principles, make sure the overall design won't crumble due to a single fatal flaw, and use default methods and parameters on the first go round. Tune when necessary.

Over time, I developed a list of ten things to look for when a database was running slow (I realize that's sloppy terminology, but it's intentional). These ten things were generally peculiar to VMS and Rdb/VMS, although some of them might port.

I think I'll start a new thread on "Self joins and optimization" so as to avoid hijacking the thread on interpolation. Received on Sat May 05 2007 - 15:17:52 CEST