Re: Re: xReader, double-effort (was: Temporary tables under hot standby)

On 5/3/12 2:54 PM, Josh Berkus wrote:
>> (2)  If logical transactions had been implemented as additions to
>> >  the WAL stream, and Slony was using that, do you think they would
>> >  still have been usable for this recovery?
> Quite possibly not.

The key advantage that I see in londiste/slony replication is that your data stream has absolutely nothing to do with
anythingbinary or internal to Postgres. That means that the only way corruption will travel from a master to a slave is
ifthe corruption is in the actual fields being updated, and even that's not a given (ie: UPDATING a field to a
completelynew value would not propagate corruption even if the old value of the field was corrupted).
 

So, embedding a logical stream into WAL is not inherently bad... what would be bad is if that "logical" stream was
susceptibleto corruption due to something like full page writes. Simply embedding the exact same info slony or londiste
capturesinto the WAL should be fine (though likely defeats the purpose). Translating binary WAL data into DML
statementswould very likely allow corruption to travel from master to slave.
 
-- 
Jim C. Nasby, Database Architect                   jim@nasby.net
512.569.9461 (cell)                         http://jim.nasby.net