Re: Postgres-R: tuple serialization

On Jul 22, 2008, at 4:43 PM, Markus Wanner wrote:
> Decibel! wrote:
>> ISTM that both londiste and Slony would be able to make use of  
>> these improvements as well. A modular replication system should be  
>> able to use a variety of methods for logging data changes and then  
>> applying them on a subscriber, so long as some kind of common  
>> transport can be agreed upon (such as text). So having a change  
>> capture and apply mechanism that isn't dependent on a lot of extra  
>> stuff would be generally useful to any replication mechanism.
>
> Hm.. yeah, that's a good hint. However, I'm not sure how londiste  
> and Slony would interface with these internal methods. That would  
> require some sort of special replication triggers or something. But  
> when to fire them? After every statement (sync)? Just before commit  
> (eager)? After commit (lazy)? (These are the points in Postgres-R,  
> where the internal methods are called).

Currently, londiste triggers are per-row, not deferred. IIRC,  
londiste is the same. ISTM it'd be much better if we had per- 
statement triggers that could see what data had changed; that'd  
likely be a lot more efficient than doing stuff per-row.

In any case, both replication systems should work with either sync or  
eager. I can't see them working with lazy.

What about just making all three available?

> I'm claiming that Postgres-R is modular (enough). But I'm unsure  
> what interface it could provide to the outer world.


Yeah. I suspect that Postgres-R could end up taking the place of the  
replica-hooks mailing list (and more, of course).
-- 
Decibel!, aka Jim C. Nasby, Database Architect  decibel@decibel.org
Give your computer some brain candy! www.distributed.net Team #1828