Re: collateral benefits of a crash-safe visibility map

On Tue, May 10, 2011 at 1:49 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On Tue, May 10, 2011 at 6:02 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> On Tue, May 10, 2011 at 12:57 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
>>> Hmmm, do we really need to WAL log freezing?
>>>
>>> Can we break down freezing into a 2 stage process, so that we can have
>>> first stage as a lossy operation and a second stage that is WAL
>>> logged?
>>
>> That might solve the relfrozenxid problem - set the bits in the heap,
>> sync the heap, then update relfrozenxid once the heap is guaranteed
>> safely on disk - but it again seems problematic for Hot Standby.
>
> How about we truncate the clog differently on each server? We could
> have a special kind of VACUUM that runs during Hot Standby, setting
> frozen hint bits only.

Interesting idea.  It does seem complicated.

-- 
Robert Haas
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