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Re: Another idea for dealing with cmin/cmax

From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
To: Martijn van Oosterhout <kleptog(at)svana(dot)org>
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 09:59:13
Message-ID: 451CEE71.40600@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-hackers
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);

-- 
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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