Re: clustering without locking

From: Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>
To: Scott Ribe <scott_ribe(at)killerbytes(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: clustering without locking
Date: 2008-05-02 14:09:01
Message-ID: 481B207D.2030207@postnewspapers.com.au
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Scott Ribe wrote:
>> Huh? If I'm understanding you correctly you'll end up with rows in
>> order, but with a really big hole in the middle of the table. I'm not
>> sure if that qualifies as "clusters".
>>
>
> That's why he said vacuum when done. Anyway, I'm not sure that a big
> *contiguous* hole in the middle of the table would matter as much for
> queries, because most rows would still be close to each other--most queries
> would pull from one side or other of the hole, and even for those that
> didn't, it would be one seek across the hole, not seeking all over the
> place?
>

Wouldn't new / updated tuples just get put in the hole, fairly rapidly
un-clustering the table again?

I guess you could also have a fillfactor to pad out the newly clustered
data and just accept huge disk space use.

When you ran the lockless cluster again it could also fill the hole in
partly.

--
Craig Ringer

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