Stefan Kaltenbrunner wrote:
> Heikki Linnakangas wrote:
>
>> 2. Pointer swinging. At the moment, after a row is HOT updated, the only
>> way to get rid of the redirecting line pointer is to run VACUUM FULL or
>> CLUSTER (or delete or cold update the row and vacuum). If we want to
>> implement pointer swinging before release, we have to get started now.
>> If we're happy to release without it and address the issue in later
>> releases if it seems important, we need to make a conscious decision on
>> that, now. I personally think we can release without it.
>>
> hmm - I don't really understand most of the stuff behind HOT but does
> this mean that VACUUM FULL (or CLUSTER) is becoming a recommended or
> even required routine maintenance task for people using HOT ?
>
No more than before. See the comment "or delete or cold update the row
and vacuum". The row couldn't be cleared by vacuum before unless
delete/update. Based on the above, it appears that every time an HOT
update occurs, 4 to 8 bytes might get wasted in the page. Eventually
this fills the page and a regular cold update is required and it is cleared.
Cheers,
mark
--
Mark Mielke <mark@mielke.cc>