From: | Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> |
---|---|
To: | Magnus Hagander <magnus(at)hagander(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Avoid full page images in streaming replication? |
Date: | 2015-10-22 21:57:47 |
Message-ID: | 56295BDB.6030200@BlueTreble.com |
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Thread: | |
Lists: | pgsql-hackers |
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
Data in Trouble? Get it in Treble! http://BlueTreble.com
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