Markus Wanner wrote: > Gregory Stark wrote:
>> It would be nice if there was a way for Slony to express to the server that >> really, it only needs any UNIQUE NOT NULL combination of columns to match. >> Once the server has any such combination which matches it can skip checking >> the rest. I can't think of any way to write such a query in SQL. > > I don't quite get your point here. For UPDATEs which change the PRIMARY > KEY, the sender currently sends the *old* values plus the changes. In > that case, you certainly don't want to send the entire olde tuple, but > only the fields for *one* KEY. That's what I'm calling the replication > key. (And currently equals the PRIMARY KEY). I think the point here is that you need to distinguish which tuple you need to update. For this, our Replicator uses the primary key only; there's no way to use another candidate key (unique not null). It would certainly be possible to use a different candidate key, but as far as I know no customer has ever requested this. (FWIW we don't send the old values -- only the original PK columns, the values of columns that changed, and the "update mask" in terms of heap_modify_tuple.) -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
