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

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Bernd Helmle <mailings@oopsware.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, KaiGai Kohei <kaigai@kaigai.gr.jp>, KaiGai Kohei <kaigai@ak.jp.nec.com>, pgsql-hackers@postgresql.org, Thom Brown <thombrown@gmail.com>, Alvaro Herrera <alvherre@commandprompt.com>
Date: 2010-01-24T19:30:30Z
Lists: pgsql-hackers 
On Sun, Jan 24, 2010 at 2:01 PM, Bernd Helmle <mailings@oopsware.de> 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, 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