From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
Cc: | Greg Stark <stark(at)mit(dot)edu>, Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: First-draft release notes for next week's releases |
Date: | 2014-03-18 00:01:00 |
Message-ID: | 11964.1395100860@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On 2014-03-17 19:55:01 -0400, Tom Lane wrote:
>>> I think the best way to really cleanup a table is to use something like:
>>> ALTER TABLE rew ALTER COLUMN data TYPE text USING (data);
>> Um... don't we have logic in there that's smart enough to short-circuit
>> that?
> Not with USING present I think?
regression=# create table foo as select generate_series(1,1000000) as data;
SELECT 1000000
Time: 575.113 ms
regression=# alter table foo alter column data type int4 using (data);
ALTER TABLE
Time: 1001.859 ms
regression=# alter table foo alter column data type int4 using (data);
ALTER TABLE
Time: 0.821 ms
regression=# alter table foo alter column data type int8 using (data);
ALTER TABLE
Time: 677.810 ms
regression=# alter table foo alter column data type int8 using (data);
ALTER TABLE
Time: 1.085 ms
Looks like it's smart enough to me.
regards, tom lane
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