digoal
2021-08-01
PostgreSQL , 逻辑复制
Improve documentation for START_REPLICATION ... LOGICAL.
author Jeff Davis <jdavis@postgresql.org>
Fri, 30 Jul 2021 21:59:19 +0000 (14:59 -0700)
committer Jeff Davis <jdavis@postgresql.org>
Fri, 30 Jul 2021 22:12:20 +0000 (15:12 -0700)
commit 14d474e079e1edf08926a2e68028cbd82dd614c4
tree 0f9c5e15e184cb7adb1395f6dabcf738f691a963 tree
parent 5fcf3945bd90bb0170938ad780159779367dc8ac commit | diff
Improve documentation for START_REPLICATION ... LOGICAL.
The starting point may not be exactly what the client requested; it
may be at the slot's confirmed_flush_lsn.
Also, upgrade the message from DEBUG1 to LOG when this happens.
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/c5c861d576f2511732f8002c76245da587110b1c.camel%40j-davis.com
doc/src/sgml/protocol.sgml diff | blob | blame | history
src/backend/replication/logical/logical.c diff | blob | blame | history
+ Instructs server to start streaming WAL for logical replication,
+ starting at either WAL location <replaceable
+ class="parameter">XXX/XXX</replaceable> or the slot's
+ <literal>confirmed_flush_lsn</literal> (see <xref
+ linkend="view-pg-replication-slots"/>), whichever is greater. This
+ behavior makes it easier for clients to avoid updating their local LSN
+ status when there is no data to process. However, starting at a
+ different LSN than requested might not catch certain kinds of client
+ errors; so the client may wish to check that
+ <literal>confirmed_flush_lsn</literal> matches its expectations before
+ issuing <literal>START_REPLICATION</literal>.
+ </para>
+
+ <para>
+ The server can reply with an error, for example if the
+ slot does not exist. On success, server responds with a CopyBothResponse
https://www.postgresql.org/docs/14/view-pg-replication-slots.html
confirmed_flush_lsn pg_lsn:
The address (LSN) up to which the logical slot's consumer has confirmed receiving data. Data older than this is not available anymore. NULL for physical slots.
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