NAME

       LOCK SET - Guard Slony-I replication set to prepare for MOVE SET

SYNOPSIS

       LOCK SET (options);

DESCRIPTION

       Guards  a  replication  set against client application updates in preparation for a SLONIK
       MOVE SET(7) 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(p_set_id integer)” [not available as a man page].

EXAMPLE

       LOCK SET (
          ID = 1,
          ORIGIN = 3
       );

LOCKING BEHAVIOUR

       Exclusive  locks  on  each  replicated  table  will  be  taken out on the origin node, and
       triggers are added to each such table that reject table updates.

SLONIK EVENT CONFIRMATION BEHAVIOUR

       Slonik does not wait for event confirmations before performing this command.

VERSION INFORMATION

       This command was introduced in Slony-I 1.0

                                         1 November 2021                       SLONIK LOCK SET(7)