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Re: [BUG?] strange behavior in ALTER TABLE ... RENAME TO on inherited columns

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Bernd Helmle <mailings(at)oopsware(dot)de>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, KaiGai Kohei <kaigai(at)kaigai(dot)gr(dot)jp>, KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>, pgsql-hackers(at)postgresql(dot)org, Thom Brown <thombrown(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Subject: Re: [BUG?] strange behavior in ALTER TABLE ... RENAME TO on inherited columns
Date: 2010-01-24 19:30:30
Message-ID: 603c8f071001241130g727ef037rea8035f3163c5174@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sun, Jan 24, 2010 at 2:01 PM, Bernd Helmle <mailings(at)oopsware(dot)de> wrote:
> --On 24. Januar 2010 19:45:33 +0100 Bernd Helmle <mailings(at)oopsware(dot)de>
> wrote:
>>  I don't see where this should be related to the number of tables not
>> part of the inheritance tree (or inheritance at all).
> To answer that myself: it seems get_attname() introduces the overhead here
> (forgot about that). Creating additional 16384 tables without any connection
> to the inheritance increases the times on my Phenom-II Box to round about 2
> seconds:
>
> Current -HEAD
>
> bernd=# ALTER TABLE a1 RENAME COLUMN acol1 TO xyz;
> ALTER TABLE
> Time: 409,045 ms
>
> With KaiGai's recent patch:
>
> bernd=# ALTER TABLE a1 RENAME COLUMN acol1 TO xyz;
> ALTER TABLE
> Time: 2402,306 ms

Hmm, so adding those tables slowed down HEAD by <50%, but the time
with KaiGai's patch more than trippled.  So I think we definitely need
KaiGai to try it the other way and see how that shakes out...

...Robert

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