Re: Freezing without write I/O

On 06/07/2013 08:56 PM, Heikki Linnakangas wrote:
> On 07.06.2013 21:33, Simon Riggs wrote:
>> Now that I consider Greg's line of thought, the idea we focused on
>> here was about avoiding freezing. But Greg makes me think that we may
>> also wish to look at allowing queries to run longer than one epoch as
>> well, if the epoch wrap time is likely to come down substantially.
>>
>> To do that I think we'll need to hold epoch for relfrozenxid as well,
>> amongst other things.
>
> The biggest problem I see with that is that if a snapshot can be older
> than 2 billion XIDs, it must be possible to store XIDs on the same
> page that are more than 2 billion XIDs apart. 
It could be possible to recognise the situation and save the new XIDs on
*another* page ?


-- 
Hannu Krosing
PostgreSQL Consultant
Performance, Scalability and High Availability
2ndQuadrant Nordic OÜ