On 12/12/2006 2:22 PM, Andreas Kostyrka wrote:
> Ok, so how does the 
> psql -c 'alter table x add column y text;' -h slave
> psql -c 'alter table x add column y text;' -h master
> 
> break? I need to ask as I've been using it for over 6 months without
> troubles.

It breaks the masters idea of the tables key/value layout. I think at 
some point I added a check to the log trigger that will cause any 
transactions from there on to simply bail out with an error, so you 
probably want to stay with your current Slony version and not upgrade 
any more.

> <sarcasm source=some_devs_at_the_office>
> Well, mysql seems to have "sensible" replication that handles DDLs
> sensibly. Well, that's why PostgreSQL and slony are scheduled here to
> be phased out ;)
> </sarcasm>

Well, MySQL has replication that is limited to applications treating the 
database as a stupid byte container anyways. All the glorious new 
features like stored procedures and triggers are incompatible with their 
replication. If your application belongs to that category of software, 
why are you bothering to use Postgres in the first place?

> Yes, it's possible to do planned shutdowns. It's just very bothersome,
> and doesn't look to well, when all the other components are being
> optimized for upgrades under load, and I need to kill the DB
> connections to add a field? While I can rollout major upgrades to the
> application without interrupting service?

A well designed application does not hog the database with idle 
transactions in progress for hours. Locking tables, doing the schema 
changes and unlocking them again should not require to kill any DB 
connections. Note that Postgres' own vacuum as well as the currently 
developed frequent update optimization don't play nicely with that either.


Jan

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