Re: Avoid full page images in streaming replication?

On 10/22/15 4:42 PM, Magnus Hagander wrote:
>  > How are you going to make that work without LSNs in the WAL received by
>  > the replica diverging from those in the master's WAL?
>  >
>
> We could in theory send a "this would be been a fpi but it's skipped"
> record which would only exist in streaming and just make the standby
> write a noop of some kind? It would still be on the standby but it would
> at least not consume the bandwidth. Just skip sending the actual
> contents of the fpi.

I don't think it can be a noop on the receiver though... doesn't the 
receiver still need full page images in case of a crash? (Assuming 
full_page_writes is enabled...)

The other issue is chained replicas, where one of the children may need 
full page writes (during initial copy).
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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