MIME-Version: 1.0
From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Wed, 4 Mar 2026 08:55:13 -0700
Message-ID: 
 <CAKFQuwY=WLF0OH8JE5T8S=aj0LBydiSn02fkRE73Sm_KSLRqJQ@mail.gmail.com>
Subject: doc: Improve wal_level and effective_wal_level GUC around logical
 replication
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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 <https://www.postgresql.org/message-id/CAKFQuwY%3DWLF0OH8JE5T8S%3Daj0LBydiSn02fkRE73Sm_KSLRqJQ%40mail.gmail.com>
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Hi,

In evaluating the proposed change to wal_level docs in [1] I found it to be
undesirable, but the discussion and my own review discovered some other
changes that should be considered.

Since effective_wal_level now exists, Logical Replication Getting Started
needs to be updated.
Add links to the main topics that the different levels apply to.
Be explicit about the ordering of minimal, replica, and logical.
Move the behavior of effective_wal_level to the GUC for it, leaving behind
just the pointer that wal_level is now just a "minimum".

David J.

[1]
https://www.postgresql.org/message-id/CA%2Bv5N42vKtY17653eBHFx%2BCw06E2fSmPrXmX2qKYG23%3D4Ycd7A%40mail.gmail.com

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<div dir=3D"ltr"><div class=3D"gmail_default" style=3D"font-family:arial,he=
lvetica,sans-serif">Hi,</div><div class=3D"gmail_default" style=3D"font-fam=
ily:arial,helvetica,sans-serif"><br></div><div class=3D"gmail_default" styl=
e=3D"font-family:arial,helvetica,sans-serif">In evaluating the proposed cha=
nge to wal_level docs in [1] I found it to be undesirable, but the discussi=
on and my own review discovered some other changes that should=C2=A0be cons=
idered.</div><div class=3D"gmail_default" style=3D"font-family:arial,helvet=
ica,sans-serif"><br></div><div class=3D"gmail_default" style=3D"font-family=
:arial,helvetica,sans-serif">Since effective_wal_level now exists, Logical=
=C2=A0Replication Getting Started needs to be updated.</div><div class=3D"g=
mail_default" style=3D"font-family:arial,helvetica,sans-serif">Add links to=
 the main topics that the different levels apply=C2=A0to.</div><div class=
=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif">Be expl=
icit about the ordering of minimal, replica, and logical.</div><div class=
=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif">Move th=
e behavior of effective_wal_level to the GUC for it, leaving behind just th=
e pointer that wal_level is now just a &quot;minimum&quot;.</div><div class=
=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif"><br></d=
iv><div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-s=
erif">David J.</div><div class=3D"gmail_default" style=3D"font-family:arial=
,helvetica,sans-serif"><br></div><div class=3D"gmail_default" style=3D"font=
-family:arial,helvetica,sans-serif">[1]=C2=A0<a href=3D"https://www.postgre=
sql.org/message-id/CA%2Bv5N42vKtY17653eBHFx%2BCw06E2fSmPrXmX2qKYG23%3D4Ycd7=
A%40mail.gmail.com">https://www.postgresql.org/message-id/CA%2Bv5N42vKtY176=
53eBHFx%2BCw06E2fSmPrXmX2qKYG23%3D4Ycd7A%40mail.gmail.com</a></div></div>

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