[Bucardo-general] Automatic Cascading Replication
David E. Wheeler
david at justatheory.com
Wed Dec 19 17:20:33 UTC 2012
On Dec 19, 2012, at 7:48 AM, Greg Sabino Mullane <greg at endpoint.com> wrote:
> Frobishers (let's call it C, ok? :) will not be up to date if A goes down,
> if the second sync is:
> table=customers dbs=A:source B:source C:target
> Bucardo cannot push out to C unless A and B are both available. What you
> would need is three syncs:
> 1) MM between lots of tables A:source B:source
> 2) One-way customer table only A:source C:target
> 3) One-way customer table only B:source C:target
> And of course customer table should have makedelta:A,B
Oh. So everything will be replicated to C twice? Ick.
> Well, even if one were to do this (and I am not convinced), we would
> need to use seomthing other than session_replication_role. Because
> setting it to "local" means that all *other* rules and triggers
> would fire, something definitely not wanted.
Excellent point. I should have thought of that.
>>> Yeah, but that still means firing that trigger for every single row
>>> on the bulk insert. Not so bulky anymore. :)
>> I don’t know what the actual overhead on that is, do you? I mean,
>> compared to the I/O required when a COPY happens, is it significant?
> I don't know the numbers, no.
Might be worth some benchmarking.
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