Re: PGDOCS - Logical replication GUCs - added some xrefs - Mailing list pgsql-hackers

Hi hackers.

There is a docs Logical Replication section "31.10 Configuration
Settings" [1] which describes some logical replication GUCs, and
details on how they interact with each other and how to take that into
account when setting their values.

There is another docs Server Configuration section "20.6 Replication"
[2] which lists the replication-related GUC parameters, and what they
are for.

Currently AFAIK those two pages are unconnected, but I felt it might
be helpful if some of the parameters in the list [2] had xref links to
the additional logical replication configuration information [1]. PSA
a patch to do that.

> +    <para>
> +     For <firstterm>logical replication</firstterm> configuration settings refer
> +     also to <xref linkend="logical-replication-config"/>.
> +    </para>
> +
These settings control the behavior of the built-in streaming replication feature (see Section 27.2.5) and logical replication (link).

For physical replication, servers will be either a primary or a standby server. Primaries can send data, while standbys are always receivers of replicated data. When cascading replication (see Section 27.2.7) is used, standby servers can also be senders, as well as receivers. Parameters are mainly for sending and standby servers, though some parameters have meaning only on the primary server. Settings may vary across the cluster without problems if that is required.

For logical replication, servers will either be publishers (also called senders in the sections below) or subscribers. Publishers are ...., Subscribers are...

> +       <para>
> +         See <xref linkend="logical-replication-config"/> for more details
> +         about setting <varname>max_replication_slots</varname> for logical
> +         replication.
> +        </para>

The link doesn't add any new information regarding max_replication_slots other than "to reserve some for table sync" and has a good amount of unrelated info. I think it might be useful to just put a line here asking to reserve some for table sync instead of linking to the entire logical replication config section.

> -   Logical replication requires several configuration options to be set.
> +   Logical replication requires several configuration parameters to be set.

May not be needed? The docs have references to both options and parameters but I don't feel strongly about it. Feel free to use what you prefer.

I think we should add an additional line to the intro here saying that parameters are mostly relevant only one of the subscriber or publisher. Maybe a better written version of "While max_replication_slots means different things on the publisher and subscriber, all other parameters are relevant only on either the publisher or the subscriber."