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Re: Hash join VS sort-merge, nested loops...

From: Yong <yhuang_at_indigopool.com>
Date: 2000/08/02
Message-ID: <8ma7oe$e5$1@news.sinet.slb.com>#1/1

metalink.oracle.com requires you purchase Oracle support. It gives you more helpful information than what technet.oracle.com can. I wish it was available to all users that love Oracle.

There're many papers up there on hash joins as I checked this afternoon. I picked one that looks like the shortest. It basically says if you have a table Small and one Big and other conditions are met for hash joins, the values in table Small will be hashed into memory, unless hash_area_size is not big enough, in which case the part that doesn't fit goes into TEMP segments. Each row in Big is compared with the value in the hash table and the result is output immediately if no TEMP is not used. If TEMP is used, the result is output when all comparison is done. There's no sorting mentioned in the article and I don't believe there's any in the whole process. (I think now I can write a short program that simulates the whole hash join process based on the above understanding!)

Yong Huang
yhuang_at_indigopool.com

<sergey_s_at_my-deja.com> wrote in message news:8ma1bp$dem$1_at_nnrp1.deja.com...
>
>
> > There is a paper on metalink about hash joins and the methodology
> > used... I'd recommend having a read of that.
> >
> > HTH
> > --
> > ===========================================
> > Connor McDonald
> > http://www.oracledba.co.uk
> >
> > We are born naked, wet and hungry...then things get worse
> >
>
> Where is the metalink?
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Received on Wed Aug 02 2000 - 00:00:00 CDT

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