Re: CLUSTER can change t_len - Mailing list pgsql-hackers

From Greg Stark
Subject Re: CLUSTER can change t_len
Date
Msg-id AANLkTin6DiCOeyAwPKk73+cs9Zm-XG4KxhxdW3hx2zN=@mail.gmail.com
Whole thread Raw
In response to Re: CLUSTER can change t_len  (Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>)
Responses Re: CLUSTER can change t_len
List pgsql-hackers
On Tue, Nov 9, 2010 at 10:20 AM, Heikki Linnakangas
<heikki.linnakangas@enterprisedb.com> wrote:
>>
>> We have a comment /* be conservative */ in the function, but I'm not sure
>> we actually need the MAXALIGN. However, there would be almost no benefits
>> to keep t_len in small value because we often treat memory in MAXALIGN
>> unit.
>
> Hmm, the conservatism at that point affects the free space calculations. I'm
> not sure if it makes any difference in practice, but I'm also not sure it
> doesn't. pd_upper is always MAXALIGNed, but pd_lower is not.
>
> This would be more in line with what the main heap_insert code does:
>


Doesn't this cause assertion failures in heap_fill_tuple when the data
size isn't what's expected? I guess we never actually use the t_len
for later tuple reconstructions, we just recompute the needed size?
-- 
greg


pgsql-hackers by date:

Previous
From: Greg Stark
Date:
Subject: Re: Protecting against unexpected zero-pages: proposal
Next
From: Euler Taveira de Oliveira
Date:
Subject: pg_ctl init doc bug