Re: collateral benefits of a crash-safe visibility map

On Tue, May 10, 2011 at 6:02 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Tue, May 10, 2011 at 12:57 PM, Simon Riggs <simon(at)2ndquadrant(dot)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.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
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