Re: [HACKERS] Re: 7.0 weirdness

From: "Matthias Urlichs" <smurf(at)noris(dot)de>
To: Jeff MacDonald <jeff(at)pgsql(dot)com>
Cc: omid omoomi <oomoomi(at)hotmail(dot)com>, pgsql-sql(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] Re: 7.0 weirdness
Date: 2000-05-30 14:31:35
Message-ID: 20000530163135.P25517@noris.de
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Hi,

Jeff MacDonald:
> gid is unique.. it's a serial..
>
Then there is no point in using "DISTINCT" in the first place, is there?

> funny thing is tho this worked on 6.5

It happened to work because your gid is unique. But in the general case,
it can't work. Consider this table:

gid created
X 1
Y 2
X 3

Now, should your query's result be

gid
X
Y

or should it be

gid
Y
X

? And since the typical implementation throws away non-selected-for
columns before UNIQUEing, how should it be able to sort anything?

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Matthias Urlichs | noris network GmbH | smurf(at)noris(dot)de | ICQ: 20193661
The quote was selected randomly. Really. | http://smurf.noris.de/
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