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

From: KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>
To: Bernd Helmle <mailings(at)oopsware(dot)de>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, KaiGai Kohei <kaigai(at)kaigai(dot)gr(dot)jp>, 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 23:45:38
Message-ID: 4B5CDBA2.4080600@ak.jp.nec.com (view raw or flat)
Thread:
Lists: pgsql-hackers
(2010/01/25 4:01), Bernd Helmle 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....

Bernd, could you try same test with previous patch?
  http://archives.postgresql.org/message-id/4B41BB04.2070609@ak.jp.nec.com

It computes an expected inhcount during find_all_inheritors(), and
compares it with the target pg_attribute entry?

I'll also try to measure performance in three cases by myself.
Please wait for a while...

Thanks,
-- 
OSS Platform Development Division, NEC
KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>

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