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Re: Column Filtering in Logical Replication

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, Rahila Syed <rahilasyed90@gmail.com>, Peter Smith <smithpb2250@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2022-01-06T12:22:54Z
Lists: pgsql-hackers 
On 2022-Jan-06, Amit Kapila wrote:

> On Mon, Jan 3, 2022 at 8:01 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> >
> 
> fetch_remote_table_info()
> {
> ..
> + appendStringInfo(&cmd,
> + "  SELECT pg_catalog.unnest(prattrs)\n"
> + "    FROM pg_catalog.pg_publication p JOIN\n"
> + "         pg_catalog.pg_publication_rel pr ON (p.oid = pr.prpubid)\n"
> + "   WHERE p.pubname IN (%s) AND\n",
> + publications.data);
> + if (!am_partition)
> + appendStringInfo(&cmd, "prrelid = %u", lrel->remoteid);
> + else
> + appendStringInfo(&cmd,
> + "prrelid IN (SELECT relid\n"
> + "    FROM pg_catalog.pg_partition_tree(pg_catalog.pg_partition_root(%u)))",
> + lrel->remoteid);
> 
> IIUC, this doesn't deal with cases when some publication has not
> specified table attrs. In those cases, I think it should return all
> attrs?

Hmm, no, the idea here is that the list of columns should be null; the
code that uses this result is supposed to handle a null result to mean
hat all columns are included.

> Also, it is not very clear to me what exactly we want to do
> with partitions?

... Hmm, maybe there is a gap in testing here, I'll check; but the idea
is that we would use the column list of the most immediate ancestor that
has one, if the partition itself doesn't have one.  (I see we're missing
a check for "pubviaroot", which should represent an override.  Need more
tests here.)

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Uno puede defenderse de los ataques; contra los elogios se esta indefenso"

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Doc: Explain about Column List feature.

  2. Doc: fix column list vs. replica identity rules.

  3. Prohibit combining publications with different column lists.

  4. Fix the check to limit sync workers.

  5. Wait for subscription to sync in t/031_column_list.sql

  6. Move prattrs to the pg_publication_rel section in docs

  7. Allow specifying column lists for logical replication

  8. Fix row filters with multiple publications

  9. Fix publish_as_relid with multiple publications

  10. Add some additional tests for row filters in logical replication.

  11. Add index on pg_publication_rel.prpubid

  12. Avoid using DefElemAction in AlterPublicationStmt

  13. Small cleanups related to PUBLICATION framework code

  14. Add PublicationTable and PublicationRelInfo structs

  15. Fix various concurrency issues in logical replication worker launching