31.1. Publication

31.1. Publication
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+ A publication can be defined on any physical + replication primary. The node where a publication is defined is referred to + as publisher. A publication is a set of changes + generated from a table or a group of tables, and might also be described as + a change set or replication set. Each publication exists in only one database. +

+ Publications are different from schemas and do not affect how the table is + accessed. Each table can be added to multiple publications if needed. + Publications may currently only contain tables. Objects must be added + explicitly, except when a publication is created for ALL + TABLES. +

+ Publications can choose to limit the changes they produce to + any combination of INSERT, UPDATE, + DELETE, and TRUNCATE, similar to how triggers are fired by + particular event types. By default, all operation types are replicated. +

+ A published table must have a “replica identity” configured in + order to be able to replicate UPDATE + and DELETE operations, so that appropriate rows to + update or delete can be identified on the subscriber side. By default, + this is the primary key, if there is one. Another unique index (with + certain additional requirements) can also be set to be the replica + identity. If the table does not have any suitable key, then it can be set + to replica identity “full”, which means the entire row becomes + the key. This, however, is very inefficient and should only be used as a + fallback if no other solution is possible. If a replica identity other + than “full” is set on the publisher side, a replica identity + comprising the same or fewer columns must also be set on the subscriber + side. See REPLICA IDENTITY for details on + how to set the replica identity. If a table without a replica identity is + added to a publication that replicates UPDATE + or DELETE operations then + subsequent UPDATE or DELETE + operations will cause an error on the publisher. INSERT + operations can proceed regardless of any replica identity. +

+ Every publication can have multiple subscribers. +

+ A publication is created using the CREATE PUBLICATION + command and may later be altered or dropped using corresponding commands. +

+ The individual tables can be added and removed dynamically using + ALTER PUBLICATION. Both the ADD + TABLE and DROP TABLE operations are + transactional; so the table will start or stop replicating at the correct + snapshot once the transaction has committed. +