From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
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To: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
Subject: | replication_origin and replication_origin_lsn usage on subscriber |
Date: | 2020-02-06 09:10:29 |
Message-ID: | CAA4eK1JwXaCezFw+kZwoxbLKYD0nWpC2rPgx7vUsaDAc0AZaow@mail.gmail.com |
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Lists: | pgsql-hackers |
During logical decoding, we send replication_origin and
replication_origin_lsn when we decode commit. In pgoutput_begin_txn,
we send values for these two but never used on the subscriber side.
Though we have provided a function (logicalrep_read_origin) to read
these two values but that is not used in code anywhere.
I think this is primarily for external application usage, but it is
not very clear how will they use it. As far as I understand, the
value of origin can be used to avoid loops in bi-directional
replication, and origin_lsn can be used to track how far subscriber
has recevied changes. I am not sure about this and particularly how
origin_lsn can be used in external applications.
This has come up in the discussion of the "logical streaming of large
in-progress transactions" [1]. Basically, we are not sure when to send
these values during streaming as we don't know its clear usage.
Thoughts?
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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