From: | Hannu Krosing <hannu(at)tm(dot)ee> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Re: Name for new VACUUM |
Date: | 2001-08-05 18:10:58 |
Message-ID: | 3B6D8C32.26BBC3C5@tm.ee |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Tom Lane wrote:
>
> Hannu Krosing <hannu(at)tm(dot)ee> writes:
> > Just out of curiosity - does CLUSTER currently "practically rebuild
> > a tables representation" ?
>
> CLUSTER currently *loses* most of a table's representation :-(.
> It needs work.
The easiest implememntaion of CLUSTER seems to be something along the
lines of
-- lock original table for WRITE in all backends
CREATE TABLE CLUSTERED_T
AS
SELECT * FROM ORIGINAL_T ORDER BY INDEX_COLUMNS;
-- now do a move of CLUSTERED_T -> ORIGINAL_T
-- and then REINDEX
-- flush cache in all backends
-- unlock the altered table
This would need an actual 2xSIZE + size of dead tuples of space but
would
probably be fastest in situations where heavy rearrangement is needed.
> But since the whole point of CLUSTER is to physically rearrange the
> tuples of a table, it seems to me that it's in a different category
> from VACUUM anyway.
OTOH it is the closest thing to VACUUM among "standard" SQL commands ;)
-----------------
Hannu
From | Date | Subject | |
---|---|---|---|
Next Message | Bruce Momjian | 2001-08-05 18:30:43 | Re: Idea for nested transactions / savepoints |
Previous Message | Hannu Krosing | 2001-08-05 18:00:38 | Re: Re: Name for new VACUUM |