Re: Horizontal scalability/sharding

On 09/02/2015 03:56 PM, Bruce Momjian wrote:
> On Wed, Sep 2, 2015 at 02:41:46PM -0400, Robert Haas wrote:
>> 4. Therefore, I think that we should instead use logical replication,
>> which might be either synchronous or asynchronous. When you modify
>> one copy of the data, that change will then be replicated to all other
>> nodes. If you are OK with eventual consistency, this replication can
>> be asynchronous, and nodes that are off-line will catch up when they
>> are on-line. If you are not OK with that, then you must replicate
>> synchronously to every node before transaction commit; or at least you
>> must replicate synchronously to every node that is currently on-line.
>> This presents some challenges: logical decoding currently can't
>> replicate transactions that are still in process - replication starts
>> when the transaction commits. Also, we don't have any way for
>> synchronous replication to wait for multiple nodes. But in theory
>> those seem like limitations that can be lifted. Also, the GTM needs
>> to be aware that this stuff is happening, or it will DTWT. That too
>> seems like a problem that can be solved.
>
> Can you explain why logical replication is better than binary
> replication for this use-case?
>

Selectivity?

JD

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