Horton

Re: Conflict detection and logging in logical replication

shveta malik <shveta.malik@gmail.com>

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From: shveta malik <shveta.malik@gmail.com>
To: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Nisha Moond <nisha.moond412@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Dilip Kumar <dilipbalaut@gmail.com>, Jan Wieck <jan@wi3ck.info>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, shveta malik <shveta.malik@gmail.com>
Date: 2024-08-19T03:37:51Z
Lists: pgsql-hackers 
On Sun, Aug 18, 2024 at 2:27 PM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> Attach the V16 patch which addressed the comments we agreed on.
> I will add a doc patch to explain the log format after the 0001 is RFC.
>

Thank You for addressing comments. Please see this scenario:

create table tab1(pk int primary key, val1 int unique, val2 int);

pub: insert into tab1 values(1,1,1);
sub: insert into tab1 values(2,2,3);
pub: update tab1 set val1=2 where pk=1;

Wrong 'replica identity' column logged? shouldn't it be pk?

ERROR:  conflict detected on relation "public.tab1": conflict=update_exists
DETAIL:  Key already exists in unique index "tab1_val1_key", modified
locally in transaction 801 at 2024-08-19 08:50:47.974815+05:30.
Key (val1)=(2); existing local tuple (2, 2, 3); remote tuple (1, 2,
1); replica identity (val1)=(1).

thanks
Shveta

Commits

  1. Rename the conflict types for the origin differ cases.

  2. Doc: explain the log format of logical replication conflicts.

  3. Log the conflicts while applying changes in logical replication.

  4. Avoid duplicate table scans for cross-partition updates during logical replication.