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Re: Re: Any optimizations to the join code in 7.1?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: lockhart(at)fourpalms(dot)org
Cc: "mascarm(at)mascari(dot)com" <mascarm(at)mascari(dot)com>, "'pgsql-hackers(at)postgresql(dot)org'" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Re: Any optimizations to the join code in 7.1?
Date: 2001-04-30 15:22:16
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu> writes:
> But it is possible, under many circumstances, for query optimization to
> be a benefit for a many-table query. The docs indicate that explicit
> join syntax bypasses that, even for inner joins, so you may find that
> this syntax is a net loss in performance depending on the query and your
> choice of table order.

> Presumably we will be interested in making these two forms of inner join
> equivalent in behavior in a future release. Tom, what are the
> impediments we might encounter in doing this?

I don't think there are any real technical problems in the way; it's
simply an implementation choice not to treat INNER JOIN the same as an
implicit join list.  I did it that way in 7.1 mainly as a flyer, to see
how many people would think it's a feature vs. how many think it's a
bug.  The votes aren't all in yet, but here we have Mike apparently
pretty pleased with it, while I recall at least one other person who
was not happy with the 7.1 behavior.

			regards, tom lane

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