On 27 May 2014 03:49, Fujii Masao <masao.fu...@gmail.com> wrote:

>> So that gives us a few approaches
>> * Compressing FPWs gives A
>> * Background FPWs gives us B
>>    which look like we can combine both ideas
>> * Double-buffering would give us A and B, but not C
>>    and would be incompatible with other two ideas
> Double-buffering would allow us to disable FPW safely but which would make
> a recovery slow. So if we adopt double-buffering, I think that we would also
> need to overhaul the recovery.

Which is also true of Background FPWs

So our options are

1. Compressed FPWs only

2. Compressed FPWs plus BackgroundFPWs plus Recovery Buffer Prefetch

3. Double Buffering plus Recovery Buffer Prefetch

IIRC Koichi had a patch for prefetch during recovery. Heikki, is that
the reason you also discussed changing the WAL record format to allow
us to identify the blocks touched by recovery more easily?

 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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