| From: | Hannu Krosing <hannu(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndQuadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Andres Freund <andres(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Freezing without write I/O |
| Date: | 2013-06-07 20:21:12 |
| Message-ID: | 51B240B8.4090502@2ndQuadrant.com |
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| Thread: | |
| Lists: | pgsql-hackers |
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
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