This patch adds a new SUBSCRIPTION parameter "origin". It specifies
whether the subscription will request the publisher to only send changes
that don't have an origin or send changes regardless of origin. Setting it
to "none" means that the subscription will request the publisher to only
send changes that have no origin associated. Setting it to "any" means
that the publisher sends changes regardless of their origin. The default
is "any".
Usage:
CREATE SUBSCRIPTION sub1 CONNECTION 'dbname=postgres port=9999'
PUBLICATION pub1 WITH (origin = none);
This can be used to avoid loops (infinite replication of the same data)
among replication nodes.
This feature allows filtering only the replication data originating from
WAL but for initial sync (initial copy of table data) we don't have such a
facility as we can only distinguish the data based on origin from WAL. As
a follow-up patch, we are planning to forbid the initial sync if the
origin is specified as none and we notice that the publication tables were
also replicated from other publishers to avoid duplicate data or loops.
We forbid to allow creating origin with names 'none' and 'any' to avoid
confusion with the same name options.
Author: Vignesh C, Amit Kapila
Reviewed-By: Peter Smith, Amit Kapila, Dilip Kumar, Shi yu, Ashutosh Bapat, Hayato Kuroda
Discussion: https://postgr.es/m/CALDaNm0gwjY_4HFxvvty01BOT01q_fJLKQ3pWP9=9orqubhjcQ@mail.gmail.com
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