Re: PG DOCS - logical replication filtering

On Wed, Mar 2, 2022 at 8:00 PM Peter Eisentraut
<peter(dot)eisentraut(at)enterprisedb(dot)com> wrote:
>
> On 02.03.22 05:47, Peter Smith wrote:
> > This patch introduces a new "Filtering" page to give a common place
> > where all kinds of logical replication filtering can be described.
> > (e.g. It is envisaged that a "Column Filters" section can be added
> > sometime in the future).
>
> The pending feature to select a subset of table columns to replicate is
> not "column filtering". The thread might still be still called that,
> but we have changed the patch to not use that terminology.
>
> Filtering is a dynamic action based on actual values. The row filtering
> feature does that. The column list feature is a static DDL-time
> configuration. It is no more filtering than specifying a list of tables
> in a publication is table filtering.
>
> So please consider organizing the documentation differently to not
> create this confusion.
>

+1. I think Row Filters can directly be a section just before
Conflicts on the logical replication page [1].

Some comments on the patch:
1. I think we can extend/add the example to have filters on more than
one table. This has been noticed multiple times during development
that people are not very clear on it.
2. I think we can add an example or two for row filters actions (like
Insert, Update).
3.
Publications can choose to limit the changes they produce to
any combination of <command>INSERT</command>, <command>UPDATE</command>,
- <command>DELETE</command>, and <command>TRUNCATE</command>,
similar to how triggers are fired by
- particular event types. By default, all operation types are replicated.
+ <command>DELETE</command>, and <command>TRUNCATE</command> by using
+ <quote>operation filters</quote>.

By this, one can imply that row filters are used for Truncate as well
but that is not true. I know that that patch later specifies that "Row
filters have no effect for <command>TRUNCATE</command> commands." but
the above modification is not very clear.

[1] - https://www.postgresql.org/docs/devel/logical-replication.html

--
With Regards,
Amit Kapila.