Re: Column Filtering in Logical Replication - Mailing list pgsql-hackers

From Rahila Syed
Subject Re: Column Filtering in Logical Replication
Date
Msg-id CAH2L28uU2yPSnRGcM-BU3HFKL6NS3LTeLjgACz6kvNBR6wQA1Q@mail.gmail.com
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In response to Re: Column Filtering in Logical Replication  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
Responses Re: Column Filtering in Logical Replication  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
List pgsql-hackers
Hi,

Thank you for updating the patch. The regression tests and tap tests pass with v9 patch.



After working on this a little bit more, I realized that this is a bad
idea overall.  It causes lots of complications and it's just not worth
it.  So I'm back at my original thought that we need to throw an ERROR
at ALTER TABLE .. DROP COLUMN time if the column is part of a
replication column filter, and suggest the user to remove the column
from the filter first and reattempt the DROP COLUMN.

This means that we need to support changing the column list of a table
in a publication.  I'm looking at implementing some form of ALTER
PUBLICATION for that.


I think right now the patch contains support only for ALTER PUBLICATION.. ADD TABLE with column filters.
In order to achieve changing the column lists of a published table, I think we can extend the
ALTER TABLE ..SET TABLE syntax to support specification of column list.

So this whole thing can
be reduced to just this:

if (att_map != NULL && !bms_is_member(att->attnum, att_map))
       continue;        /* that is, don't send this attribute */

I agree the condition can be shortened now. The long if condition was included because initially the feature
allowed specifying filters without replica identity columns(sent those columns internally without user
having to specify).

 900 +        * the table is partitioned.  Run a recursive query to iterate through all
 901 +        * the parents of the partition and retreive the record for the parent
 902 +        * that exists in pg_publication_rel.
 903 +        */

The above comment in fetch_remote_table_info() can be changed as the recursive query
is no longer used.

Thank you,
Rahila Syed

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