LOCK SET — Guard Slony-I replication
set to prepare for MOVE SET
LOCK SET (options);
Guards a replication set against client application updates in preparation for a MOVE SET command.
This command must be the first in a possible statement
group (try
). The reason for this is that it
needs to commit the changes made to the tables (adding a special
trigger function) before it can wait for every concurrent
transaction to finish. At the same time it cannot hold an open
transaction to the same database itself since this would result in
blocking itself forever.
Note that this is a locking operation, which means that it can get stuck behind other database activity.
The operation waits for transaction IDs to advance in order that data is not missed on the new origin. Thus, if you have long-running transactions running on the source node, this operation will wait for those transactions to complete. Unfortunately, if you have another database on the same postmaster as the origin node, long running transactions on that database will also be considered even though they are essentially independent.
ID = ival
ID of the set to lock
ORIGIN = ival
Node ID of the current set origin
This uses schemadoclockset( integer ).