Replicating changes

Hello list,

We're investigating a ways to replicate changes to the database to 
several "outside" systems.

Some filtering will need to take place, as not all changes are allowed 
to go to all systems. Whether the system receiving the changes stores 
them in a database or not isn't particularly relevant to us. We're only 
interested in getting the data out in a specified format.

The changes in the data that needs to be replicated can come in bursts 
of several thousands of records. Performance is important, but 
reliability as well. We need to get those changes to a number of 3rd 
parties, in a format that we're allowed to specify.

So far we've looked into a few solutions:
1.) Adding triggers to the relevant tables that send a NOTIFY and store 
the changes in a local table. probably some meta-data will be required, 
like for example a time stamp.

2.) Use one of the existing replication systems. We're currently under 
the impression that (we've looked at Slony-I particularly) the slave 
system is supposed to be another (postgresql?) database. This wouldn't 
fit our needs, but maybe we're overlooking something?

3.) Somehow directly monitoring the WAL files, interpreting and 
detecting changes. So far we haven't found any documentation on how WAL 
files are stored, so we're not sure this is feasible.

This is a call for advice, as we're surely not the first who are trying 
to accomplish this. If any clarification is needed, please ask. We want 
to get this right.

-- 
Alban Hertroys
alban@magproductions.nl

magproductions b.v.

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