Configuration parameter and table setting requirements v7

Depending on the multi-master replication system environment, you might need certain configuration settings for the conflict resolution process to operate properly.

The following are required only for the log-based method. These do not apply to the trigger-based method.

• track_commit_timestamp. Any Postgres 10 and later database server containing a primary node must have its track_commit_timestamp configuration parameter enabled. The track_commit_timestamp parameter is located in the postgresql.conf file. If track_commit_timestamp isn't enabled, then update/update conflicts aren't automatically resolved such as by using the earliest timestamp of the conflicting transactions. As a result, these conflicting transactions are left in a pending state. See Automatic conflict resolution example for an example of how update/update conflicts are automatically resolved.
• REPLICA IDENTITY FULL. If update/update conflicts are expected to occur on a given publication table, then you must set the REPLICA IDENTITY setting for the table to FULL on every primary node. The case where update transactions occur on separate primary nodes but updating different columns in the same row isn't considered an update/update conflict. However, if REPLICA IDENTITY isn't set to FULL, then this case is recorded as an update/update conflict.

Set the REPLICA IDENTITY option to FULL using the ALTER TABLE command as shown by the following:

ALTER TABLE schema.table_name REPLICA IDENTITY FULL

The following is an example of the ALTER TABLE command:

ALTER TABLE edb.dept REPLICA IDENTITY FULL;

You can display the REPLICA IDENTITY setting with the PSQL utility using the \d+ command:

edb=# \d+ edb.dept

Table "edb.dept"
 Column |         Type          | Modifiers | Storage  | Stats target | Description
--------+-----------------------+-----------+----------+--------------+-------------
 deptno | numeric(2,0)          | not null  | main     |              |
 dname  | character varying(14) |           | extended |              |
 loc    | character varying(13) |           | extended |              |
Indexes:
    "dept_pk" PRIMARY KEY, btree (deptno)
    "dept_dname_uq" UNIQUE CONSTRAINT, btree (dname)
Referenced by:
    TABLE "emp" CONSTRAINT "emp_ref_dept_fk" FOREIGN KEY (deptno) REFERENCES dept(deptno)
    TABLE "jobhist" CONSTRAINT "jobhist_ref_dept_fk" FOREIGN KEY (deptno) REFERENCES dept(deptno) ON DELETE SET NULL
Replica Identity: FULL