Re: row filtering for logical replication
Amit Kapila <amit.kapila16@gmail.com>
Commits
GET /api/v1/messages/:b64id/commits
the thread's linked commits as JSON, with link sources.
API reference →
-
Release cache tuple when no longer needed
- ed0fbc8e5ac9 15.0 landed
-
Add some additional tests for row filters in logical replication.
- ceb57afd3ce1 15.0 landed
-
Fix one of the tests introduced in commit 52e4f0cd47.
- cfb4e209ec15 15.0 landed
-
Allow specifying row filters for logical replication of tables.
- 52e4f0cd472d 15.0 landed
-
Move scanint8() to numutils.c
- cfc7191dfea3 15.0 cited
-
Replace Test::More plans with done_testing
- 549ec201d613 15.0 cited
-
Reduce relcache access in WAL sender streaming logical changes
- 6ce16088bfed 15.0 cited
-
Small cleanups related to PUBLICATION framework code
- c9105dd3660f 15.0 cited
-
Add a view to show the stats of subscription workers.
- 8d74fc96db5f 15.0 cited
-
Allow publishing the tables of schema.
- 5a2832465fd8 15.0 cited
-
Doc: improve documentation of CREATE/ALTER SUBSCRIPTION.
- 1882d6cca161 15.0 cited
-
Add PublicationTable and PublicationRelInfo structs
- 0c6828fa987b 15.0 cited
-
Remove unused argument "txn" in maybe_send_schema().
- 93d573d86571 15.0 cited
-
Add prepare API support for streaming transactions in logical replication.
- 63cf61cdeb7b 15.0 cited
-
Unify PostgresNode's new() and get_new_node() methods
- 201a76183e20 15.0 cited
-
Use l*_node() family of functions where appropriate
- 2b00db4fb0c7 15.0 cited
-
Add support for prepared transactions to built-in logical replication.
- a8fd13cab0ba 15.0 cited
-
Restore the portal-level snapshot after procedure COMMIT/ROLLBACK.
- ef9480509622 11.13 cited
-
Rename a parse node to be more general
- 91d1f2d30210 14.0 landed
-
Remove unused column atttypmod from initial tablesync query
- 4ad31bb2ef25 14.0 landed
-
SEARCH and CYCLE clauses
- 3696a600e229 14.0 cited
On Tue, Jul 20, 2021 at 11:38 AM Greg Nancarrow <gregn4422@gmail.com> wrote:
>
> On Tue, Jul 20, 2021 at 2:25 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > Today, while studying the behavior of this particular operation in
> > other databases, I found that IBM's InfoSphere Data Replication does
> > exactly this. See [1]. I think there is a merit if want to follow this
> > idea.
> >
>
> So in this model (after initial sync of rows according to the filter),
> for UPDATE, the OLD row is checked against the WHERE clause, to know
> if the row had been previously published. If it hadn't, and the NEW
> row satisfies the WHERE clause, then it needs to be published as an
> INSERT. If it had been previously published, but the NEW row doesn't
> satisfy the WHERE condition, then it needs to be published as a
> DELETE. Otherwise, if both OLD and NEW rows satisfy the WHERE clause,
> it needs to be published as an UPDATE.
>
Yeah, this is what I also understood.
> At least, that seems to be the model when the WHERE clause refers to
> the NEW (updated) values, as used in most of their samples (i.e. in
> that database "the current log record", indicated by a ":" prefix on
> the column name).
> I think that allowing the OLD values ("old log record") to be
> referenced in the WHERE clause, as that model does, could be
> potentially confusing.
>
I think in terms of referring to old and new rows, we already have
terminology which we used at various other similar places. See Create
Rule docs [1]. For where clause, it says "Within condition and
command, the special table names NEW and OLD can be used to refer to
values in the referenced table. NEW is valid in ON INSERT and ON
UPDATE rules to refer to the new row being inserted or updated. OLD is
valid in ON UPDATE and ON DELETE rules to refer to the existing row
being updated or deleted.". We need similar things for the WHERE
clause in publication if we want special syntax to refer to old and
new rows.
I think if we use some existing way to refer to old/new values then it
shouldn't be confusing to users.
[1] - https://www.postgresql.org/docs/devel/sql-createrule.html
--
With Regards,
Amit Kapila.