| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Arthur Silva <arthurprs(at)gmail(dot)com> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: logical column ordering |
| Date: | 2015-02-27 20:02:58 |
| Message-ID: | 20150227200258.GL2384@alvh.no-ip.org |
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| Thread: | |
| Lists: | pgsql-hackers |
Arthur Silva wrote:
> Sorry to intrude, I've been following this post and I was wondering if it
> would allow (in the currently planed form or in the future) a wider set of
> non-rewriting DDLs to Postgres. For example, drop a column without
> rewriting the table.
Perhaps. But dropping a column already does not rewrite the table, only
marks the column as dropped in system catalogs, so do you have a better
example.
One obvious example is that you have
CREATE TABLE t (
t1 int,
t3 int
);
and later want to add t2 in the middle, the only way currently is to
drop the table and start again (re-creating all dependant views, FKs,
etc). With the patch you will be able to add the column at the right
place. If no default value is supplied for the new column, no table
rewrite is necessary at all.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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