| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | "tigran(dot)mkrtchyan" <tigran(dot)mkrtchyan(at)desy(dot)de>, Pg Bugs <pgsql-bugs(at)postgresql(dot)org> |
| Subject: | Re: BUG #7502: ALTER COLUMN TYPE processed even if column type matches |
| Date: | 2012-08-23 17:55:12 |
| Message-ID: | 1600.1345744512@sss.pgh.pa.us |
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| Lists: | pgsql-bugs |
Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> So the ALTER TABLE trick is not needed in 9.0, but is useful in previous
> releases. There are optimizations to avoid the table rewrite in certain
> cases in 9.2:
> http://wiki.postgresql.org/wiki/What's_new_in_PostgreSQL_9.2#Reduce_ALTER_TABLE_rewrites
> According to that page, though, a change of varchar(36) to varchar(36)
> would still require a table rewrite, which doesn't make sense to me. Is
> the wiki page inaccurate maybe?
Yeah - you can easily convince yourself by timing it that no rewrite
happens in 9.2.
regards, tom lane
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