Re: row filtering for logical replication

On Fri, Jan 14, 2022 at 5:48 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> On Thu, Jan 13, 2022 at 5:49 PM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
> >
> > 4. src/backend/replication/pgoutput/pgoutput.c - pgoutput_row_filter comments
> >
> > +
> > +/*
> > + * Change is checked against the row filter, if any.
> > + *
> > + * If it returns true, the change is replicated, otherwise, it is not.
> > + *
> > + * FOR INSERT: evaluates the row filter for new tuple.
> > + * FOR DELETE: evaluates the row filter for old tuple.
> > + * For UPDATE: evaluates the row filter for old and new tuple. If both
> > + * evaluations are true, it sends the UPDATE. If both evaluations are false, it
> > + * doesn't send the UPDATE. If only one of the tuples matches the row filter
> > + * expression, there is a data consistency issue. Fixing this issue requires a
> > + * transformation.
> > + *
> > + * Transformations:
> > + * Updates are transformed to inserts and deletes based on the
> > + * old tuple and new tuple. The new action is updated in the
> > + * action parameter. If not updated, action remains as update.
> > + *
> > + * Case 1: old-row (no match) new-row (no match) -> (drop change)
> > + * Case 2: old-row (no match) new row (match) -> INSERT
> > + * Case 3: old-row (match) new-row (no match) -> DELETE
> > + * Case 4: old-row (match) new row (match) -> UPDATE
> > + *
> > + * If the change is to be replicated this function returns true, else false.
> > + *
> > + * Examples:
> >
> > The function header comment says the same thing 2x about the return values.
> >
> > The 1st text "If it returns true, the change is replicated, otherwise,
> > it is not." should be replaced by the better wording of the 2nd text
> > ("If the change is to be replicated this function returns true, else
> > false."). Then, that 2nd text can be removed (from where it is later
> > in this same comment).
>
> Hi Hou-san, thanks for all the v64 updates!
>
> I think the above comment was only partly fixed.
>
> The v64-0001 comment still says:
> + * If it returns true, the change is replicated, otherwise, it is not.
>
...
...
>
> But maybe it is best to rearrange the whole thing like:
> "Returns true if the change is to be replicated, else false."
>

+1 to change as per this suggestion.

--
With Regards,
Amit Kapila.