MIME-Version: 1.0
From: Koen De Groote <kdg.dev@gmail.com>
Date: Fri, 23 Aug 2024 16:33:08 +0200
Message-ID: <CAGbX52H8dDW8nVC8Zxg0-HFY58fAXd93XuxC83_DPHARZkpepw@mail.gmail.com>
Subject: On a subscriber, why is last_msg_send_time in pg_stat_subscription
 sometimes null?
To: PostgreSQL General <pgsql-general@lists.postgresql.org>
Content-Type: multipart/alternative; boundary="0000000000001e80f206205aa816"
Archived-At: <https://www.postgresql.org/message-id/CAGbX52H8dDW8nVC8Zxg0-HFY58fAXd93XuxC83_DPHARZkpepw%40mail.gmail.com>
Precedence: bulk

--0000000000001e80f206205aa816
Content-Type: text/plain; charset="UTF-8"

I'm running this query:

SELECT subname, received_lsn, latest_end_lsn,
last_msg_send_time, last_msg_receipt_time
FROM pg_catalog.pg_stat_subscription;

And "last_msg_send_time" will sometimes be null. All I can find in the
documentation is that this value represents: "Send time of last message
received from origin WAL sender; NULL for parallel apply workers"

But I have no context for what parallel apply workers are or why they are
NULL sometimes and other times not.

Can anyone explain?

Regards,
Koen De Groote

--0000000000001e80f206205aa816
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div>I&#39;m running this query:</div><div><br></div><div>=
SELECT subname, received_lsn,=C2=A0latest_end_lsn,<br>last_msg_send_time, l=
ast_msg_receipt_time<br>FROM pg_catalog.pg_stat_subscription;</div><div><br=
></div><div>And &quot;last_msg_send_time&quot; will sometimes be null. All =
I can find in the documentation is that this value represents: &quot;<span =
style=3D"color:rgb(33,37,41);font-family:&quot;Open Sans&quot;,sans-serif;f=
ont-size:14.4px;font-style:normal;font-variant-ligatures:normal;font-varian=
t-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-in=
dent:0px;text-transform:none;word-spacing:0px;white-space:normal;background=
-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color=
:initial;display:inline;float:none">Send time of last message received from=
 origin WAL sender; NULL for parallel apply workers</span>&quot;</div><br><=
div>But I have no context for what parallel apply workers are or why they a=
re NULL sometimes and other times not.</div><div><br></div><div>Can anyone =
explain?</div><div><br></div><div>Regards,</div><div>Koen De Groote<br></di=
v></div>

--0000000000001e80f206205aa816--