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

Kouhei Kaigai <kaigai@ak.jp.nec.com>

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From: KaiGai Kohei <kaigai@ak.jp.nec.com>
To: Bernd Helmle <mailings@oopsware.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, KaiGai Kohei <kaigai@kaigai.gr.jp>, pgsql-hackers@postgresql.org, Thom Brown <thombrown@gmail.com>, Alvaro Herrera <alvherre@commandprompt.com>
Date: 2010-01-24T23:45:38Z
Lists: pgsql-hackers 
(2010/01/25 4:01), Bernd Helmle wrote:
> 
> 
> --On 24. Januar 2010 19:45:33 +0100 Bernd Helmle <mailings@oopsware.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@ak.jp.nec.com>