Skip site navigation (1) Skip section navigation (2)

Re: Another idea for dealing with cmin/cmax

From: Martijn van Oosterhout <kleptog(at)svana(dot)org>
To: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
Cc: ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>,"Jim C(dot) Nasby" <jim(at)nasby(dot)net>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Another idea for dealing with cmin/cmax
Date: 2006-09-29 10:05:15
Message-ID: 20060929100515.GB8702@svana.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Fri, Sep 29, 2006 at 10:59:13AM +0100, Heikki Linnakangas wrote:
> Martijn van Oosterhout wrote:
> >On Fri, Sep 29, 2006 at 09:35:31AM +0100, Heikki Linnakangas wrote:
> >>We could get rid of t_hoff, because we should always be able to
> >>calculate the header size. Then we're down to 18 bytes.
> >
> >Without t_hoff, how do you know the size of the null bitmap? You could
> >probably do it only if you assume the null bitmap, if present, always
> >covers all the columns...
> 
> I think we assume that already. heap_form_tuple reserves space for the 
> bitmap like this:
> 
>    if (hasnull)
>        len += BITMAPLEN(numberOfAttributes);

Ok, now we do an ALTER TABLE blah ADD COLUMN ..., and we have to expand
the bitmaps for the entire table?

Have a nice day,
-- 
Martijn van Oosterhout   <kleptog(at)svana(dot)org>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.

In response to

Responses

pgsql-hackers by date

Next:From: Heikki LinnakangasDate: 2006-09-29 10:08:15
Subject: Re: Another idea for dealing with cmin/cmax
Previous:From: Heikki LinnakangasDate: 2006-09-29 09:59:13
Subject: Re: Another idea for dealing with cmin/cmax

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group