Horton

Re: Proposal: Conflict log history table for Logical Replication

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: shveta malik <shveta.malik@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-12-12T09:33:47Z
Lists: pgsql-hackers

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  1. Allow logical replication conflicts to be logged to a table.

  2. Avoid orphaned objects dependencies

On Thu, Dec 11, 2025 at 7:49 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> I was considering the interdependence between the subscription and the
> conflict log table (CLT). IMHO, it would be logical to establish the
> subscription as dependent on the CLT. This way, if someone attempts to
> drop the CLT, the system would recognize the dependency of the
> subscription and prevent the drop unless the subscription is removed
> first or the CASCADE option is used.
>
> However, while investigating this, I encountered an error [1] stating
> that global objects are not supported in this context. This indicates
> that global objects cannot be made dependent on local objects.
>

What we need here is an equivalent of DEPENDENCY_INTERNAL for database
objects. For example, consider following case:
postgres=# create table t1(c1 int primary key);
CREATE TABLE
postgres=# \d+ t1
                                           Table "public.t1"
 Column |  Type   | Collation | Nullable | Default | Storage |
Compression | Stats target | Description
--------+---------+-----------+----------+---------+---------+-------------+--------------+-------------
 c1     | integer |           | not null |         | plain   |
    |              |
Indexes:
    "t1_pkey" PRIMARY KEY, btree (c1)
Publications:
    "pub1"
Not-null constraints:
    "t1_c1_not_null" NOT NULL "c1"
Access method: heap
postgres=# drop index t1_pkey;
ERROR:  cannot drop index t1_pkey because constraint t1_pkey on table
t1 requires it
HINT:  You can drop constraint t1_pkey on table t1 instead.

Here, the PK index is created as part for CREATE TABLE operation and
pk_index is not allowed to be dropped independently.

> Although making an object dependent on global/shared objects is
> possible for certain types of shared objects [2], this is not our main
> objective.
>

As per my understanding from the above example, we need something like
that only for shared object subscription and (internally created)
table.

-- 
With Regards,
Amit Kapila.