From: Dean Gibson (DB Administrator) <postgresql@ultimeth.com>
To: pgsql-performance@postgresql.org
Subject: Re: Q on views and performance
Date: Sat, 23 Feb 2008 08:49:13 -0800
Message-ID: <47C04E89.3030300@ultimeth.com> (raw)
In-Reply-To: <c2350ba40802230821t2446a151j3279b8ea901c31b3@mail.gmail.com>
References: <c2350ba40802221249h37913d0cyaa6387a93c55fe69@mail.gmail.com>
<47BF7B80.1040309@ultimeth.com>
<c2350ba40802230559l280eab73k8e79a8bda7a4994a@mail.gmail.com>
<47C03709.5010205@ultimeth.com>
<c2350ba40802230821t2446a151j3279b8ea901c31b3@mail.gmail.com>
On 2008-02-23 08:21, Kynn Jones wrote:
> ...
>
> 3. Why not write:
>
> CREATE VIEW txt AS
> SELECT a1.word AS word1, a1.type AS type1, a2.word AS word2,
> a2.type AS type2
> FROM T a1 [LEFT] JOIN T a2 USING( zipk ); -- Use "LEFT" if
> appropriate
> SELECT word1, word1
> FROM S JOIN txt ON word = word1
> WHERE type1 = <int1> AND type2 = <int2>;
>
>
> This is would indeed produce the same results as Q1, but this approach
> would require defining about 10,000 views, one for each possible pair
> of int1 and int2
Why 10,000 views??? What's wrong with the ONE view above? You DON'T
want to be defining VIEWs based on actual tables VALUES; leave that to
the SELECT. For that matter, what's wrong with the final SELECT I
listed (below)?
SELECT a1.word AS word1, a2.word AS word2
FROM S JOIN T a1 USING( word )
LEFT JOIN T a2 USING( zipk )
WHERE a1.type = <int1> AND a2.type = <int2>;
-- Dean
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To: pgsql-performance@postgresql.org
Cc: postgresql@ultimeth.com
Subject: Re: Q on views and performance
In-Reply-To: <47C04E89.3030300@ultimeth.com>
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