Re: PG DOCS - logical replication filtering

On Thu, Mar 3, 2022 at 2:15 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> 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].
>

OK. I will reorganize the page as suggested, and also attend to the
other comments below.

> 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
>

------
Kind Regards,
Peter Smith.
Fujitsu Australia.