To: pgsql-docs@lists.postgresql.org
From: Fujii Masao <masao.fujii@oss.nttdata.com>
Subject: The description for pg_replication_slots.restart_lsn
Message-ID: <6497f1e9-3148-c5da-7e49-b2fddad9a42f@oss.nttdata.com>
Date: Wed, 17 Jun 2020 23:47:28 +0900
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0)
 Gecko/20100101 Thunderbird/68.9.0
MIME-Version: 1.0
Content-Type: multipart/mixed;
 boundary="------------3545A986D5C3245B633DEED2"
Content-Language: en-US
Precedence: bulk

This is a multi-part message in MIME format.
--------------3545A986D5C3245B633DEED2
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit

Hi,

The document explains that restart_lsn column in pg_replication_slots view is:

     The address (LSN) of oldest WAL which still might be required by
     the consumer of this slot and thus won't be automatically removed
     during checkpoints.

But the latter part is not true in v13 thanks to max_slot_wal_keep_size.
I think that we need to update it as follows. Thought?

     The address (LSN) of oldest WAL which still might be required by
     the consumer of this slot and thus won't be automatically removed
     during checkpoints unless this LSN gets behind more than
     max_slot_wal_keep_size from the current LSN.

Patch attached.

Regards,
-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION

--------------3545A986D5C3245B633DEED2
Content-Type: text/plain; charset=UTF-8; x-mac-type="0"; x-mac-creator="0";
 name="pg_replication_slots_restart_lsn.patch"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
 filename="pg_replication_slots_restart_lsn.patch"
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--------------3545A986D5C3245B633DEED2--