Re: Hash Joins vs. Nested Loops

rgaffuri_at_cox.net (Ryan Gaffuri) wrote:
> Someone I was working with told me the following. I was wondering if
> anyone has any comments, because I have not seen this in any
> articles/books.
>
> He said that when he tunes he generally likes to try to force nested
> loop joins over hash joins because these tend to increase performance?
> He has done this for a long time and he said that is based on
> experience.
>
> Anyone else notice this? I have never seen this anywhere else. BTW, I
> know the difference between hash joins and nested loops and know when
> either is generally used by the optimizer.

I notice that under 9iR2 those queries which are sufficiently slow enough for me to hunt them down and inspect them, they are usually doing a hash join and getting them to use a NL speeds them up substantially. Since I don't inspect queries that aren't obnoxious, I can't say how the two join methods generally perform on the "typical" query.

Xho

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