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Re: Book Review: "SQL Tuning" by Dan Tow

From: Ryan <rgaffuri_at_cox.net>
Date: Sun, 25 Jan 2004 13:20:32 -0500
Message-ID: <PNTQb.8775$_H5.1612@lakeread06>


so do you recommend the book? It really intrigues me. It seems remarkably different from other SQL tuning books.

"Mark" <simmons_mark_at_yahoo.com> wrote in message news:5366fb41.0401250251.6a631a3_at_posting.google.com...
> I bought and read Dan Tow's book. He has a small section where he
> explains where it is best to use a HJ over NL. It didn't sound to me
> like he was too biased. Early in the book he talked a lot about using
> NL, but I figured that was because he didn't want to go into the HS/NL
> conversation yet.
>
> "Mikito Harakiri" <mikharakiri_at_iahu.com> wrote in message
news:<JYjJb.5$Ma6.111_at_news.oracle.com>...
> > "Ryan" <rgaffuri_at_cox.net> wrote in message
> > news:Dr5Jb.59057$hf1.31218_at_lakeread06...
> > > HJ with full scans of both tables routinely outperforms NJs by 1000%
or
> > more
> > > when a large number of rows are involved. Its not even close.
> >
> > I apologyse for answering to your post in small increments.
> >
> > I suspect that in your case join index is missing. Clearly, NL without
join
> > index is a very dumb method, which is extremely slow on large inner
relation
> > size.
> >
> > Now, one of the steps in HJ method is creating temporary lookup table.
That
> > table purpose is similar to join index: to eliminate full scan of inner
> > relation! To be fair to NL, we have to allow creating a temporary join
index
> > if the inner relation is large and if join index is missing. Creating
> > temporary index overhead is proportional to the relation size, so that
the
> > additional overhead is small compared to the cost of join itself.
> >
> > Finally, I'm claiming that NL (with temporary join index creation
> > enhancement) is the only method needed for main-memory databases.
Received on Sun Jan 25 2004 - 12:20:32 CST

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