Jacques Caron wrote:
> Hi,
>
> One VERY IMPORTANT point that got lost somewhere since my original 
> post on the topic: the columns added MUST NOT have ANY constraints or 
> defaults. Otherwise there are good chances it WILL break your 
> replication, especially if there are updates/inserts into the table at 
> the same time. Really think twice (or probably more times) about using 
> that method with any constraint or default, and don't do it unless you 
> understand how Slony works internally.
>
> Also it only works for adding a column. Don't try to do the same for 
> deleting a column. And changing a column's type, constraints, etc. is 
> in most cases not possible with this method either.
What the difference between adding and removing a column ? (in the case, 
there's no constraint)
>
> In short, unless you are ADDING one column WITHOUT any constraints or 
> defaults, use EXECUTE SCRIPT.
>
> Jacques.
>
> At 10:31 02/07/2008, hubert depesz lubaczewski wrote:
>
>> On Tue, Jul 01, 2008 at 08:27:32AM -0700, Shahaf Abileah wrote:
>> > Also, in certain situations you might be able to run the alter command
>> > on each of the slaves and then on the master.  E.g. if you're adding a
>> > new column that allows null values, then it might be possible to alter
>> > the slaves even while rows are being inserted into the master.  You 
>> will
>> > still be taking a lock on the table while altering it, but at least
>> > you're not locking multiple tables at a time across multiple machines.
>> > Not sure if this is recommended practice.
>>
>> it's not recommended, but it works.
>> you add column on slave, then run this on master:
>> UPDATE pg_trigger SET tgargs=substring(tgargs for 
>> octet_length(tgargs)-1)||E'v\\000' where tgname = 'TRIGGER_NAME';
>> and then add the column on master.
>>
>> best regards,
>>
>> depesz
>>
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>> http://lists.slony.info/mailman/listinfo/slony1-general
>
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