| From: | "Euler Taveira" <euler(at)eulerto(dot)com> |
|---|---|
| To: | "Tomas Vondra" <tomas(dot)vondra(at)enterprisedb(dot)com>, "Jeff Davis" <pgsql(at)j-davis(dot)com>, "Amit Kapila" <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | "Alvaro Herrera" <alvherre(at)alvh(dot)no-ip(dot)org>, "Greg Nancarrow" <gregn4422(at)gmail(dot)com>, "Peter Smith" <smithpb2250(at)gmail(dot)com>, "Rahila Syed" <rahilasyed90(at)gmail(dot)com>, "Peter Eisentraut" <peter(dot)eisentraut(at)enterprisedb(dot)com>, Önder Kalacı <onderkalaci(at)gmail(dot)com>, japin <japinli(at)hotmail(dot)com>, "Michael Paquier" <michael(at)paquier(dot)xyz>, "David Steele" <david(at)pgmasters(dot)net>, "Craig Ringer" <craig(at)2ndquadrant(dot)com>, "Tomas Vondra" <tomas(dot)vondra(at)2ndquadrant(dot)com>, "Amit Langote" <amitlangote09(at)gmail(dot)com>, "PostgreSQL Hackers" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: row filtering for logical replication |
| Date: | 2021-07-13 21:02:43 |
| Message-ID: | b6ae4ad4-4001-42d7-9ade-3cd65f7fe58c@www.fastmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Tue, Jul 13, 2021, at 4:07 PM, Tomas Vondra wrote:
> On 7/13/21 5:44 PM, Jeff Davis wrote:
> > On Tue, 2021-07-13 at 10:24 +0530, Amit Kapila wrote:
8<
> >> (c) the columns
> >> referred to in the filter should be part of PK or Replica Identity.
> >
> > Why?
> >
>
> I'm not sure either.
This patch uses the old row for DELETE operations and new row for INSERT and
UPDATE operations. Since we usually don't use REPLICA IDENTITY FULL, all
columns in an old row that are not part of the PK or REPLICA IDENTITY are NULL.
The row filter evaluates NULL to false. Documentation says
<para>
The <literal>WHERE</literal> clause should contain only columns that are
part of the primary key or be covered by <literal>REPLICA
IDENTITY</literal> otherwise, <command>DELETE</command> operations will not
be replicated. That's because old row is used and it only contains primary
key or columns that are part of the <literal>REPLICA IDENTITY</literal>; the
remaining columns are <literal>NULL</literal>. For <command>INSERT</command>
and <command>UPDATE</command> operations, any column might be used in the
<literal>WHERE</literal> clause. New row is used and it contains all
columns. A <literal>NULL</literal> value causes the expression to evaluate
to false; avoid using columns without not-null constraints in the
<literal>WHERE</literal> clause. The <literal>WHERE</literal> clause does
not allow functions and user-defined operators.
</para>
--
Euler Taveira
EDB https://www.enterprisedb.com/
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