Doc patch for Logical Replication Message Formats (PG14)

From: Brar Piening <brar(at)gmx(dot)de>
To: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Doc patch for Logical Replication Message Formats (PG14)
Date: 2021-06-21 06:56:13
Message-ID: cc70956c-e578-e54f-49e6-b5d68c89576f@gmx.de
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Hello Hackers,
while amending Npgsql to account for the Logical Streaming Replication
Protocol changes in PostgreSQL 14 I stumbled upon two documentation
inaccuracies in the Logical Replication Message Formats documentation
(https://www.postgresql.org/docs/devel/protocol-logicalrep-message-formats.html)
that have been introduced (or rather omitted) with the recent changes to
allow pgoutput to send logical decoding messages
(https://github.com/postgres/postgres/commit/ac4645c0157fc5fcef0af8ff571512aa284a2cec)
and to allow logical replication to transfer data in binary format
(https://github.com/postgres/postgres/commit/9de77b5453130242654ff0b30a551c9c862ed661).

1. The content of the logical decoding message in the 'Message' message
is prefixed with a length field (Int32) which isn't documented yet.
See
https://github.com/postgres/postgres/blob/69a58bfe4ab05567a8fab8bdce7f3095ed06b99c/src/backend/replication/logical/proto.c#L388
2. The TupleData may now contain the byte 'b' as indicator for binary
data which isn't documented yet. See
https://github.com/postgres/postgres/blob/69a58bfe4ab05567a8fab8bdce7f3095ed06b99c/src/include/replication/logicalproto.h#L83
and
https://github.com/postgres/postgres/blob/69a58bfe4ab05567a8fab8bdce7f3095ed06b99c/src/backend/replication/logical/proto.c#L558.

The attached documentation patch fixes both.

Best regards,

Brar

Attachment Content-Type Size
protocol-logicalrep-message-formats-pg14-fix.patch text/plain 823 bytes

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