Re: BUG #19359: Row level security: Upserts require insert policies in the update path

Hi, Thanks for reporting!

On Fri, Dec 19, 2025 at 2:50 AM PG Bug reporting form <
noreply@postgresql.org> wrote:

> The following bug has been logged on the website:
>
> Bug reference:      19359
> Logged by:          Elena Krippner
> Email address:      elena@cedardb.com
> PostgreSQL version: 18.1
> Operating system:   Ubuntu 25.10
> Description:
>
> The documentation on policies
> (https://www.postgresql.org/docs/current/sql-createpolicy.html) says for
> upserts:
> Note that INSERT with ON CONFLICT DO UPDATE checks INSERT policies' WITH
> CHECK expressions only for rows appended to the relation by the INSERT
> path.
>
> In this case, the update path is taken, but the values can only be upserted
> after adding an insert policy:
> root@4284b66b43be:/# psql -h localhost -U postgres
> psql (18.1 (Debian 18.1-1.pgdg13+2))
> Type "help" for help.
>
> postgres=# create table t (a integer primary key);
> CREATE TABLE
> postgres=# insert into t values (1), (2), (3);
> INSERT 0 3
> postgres=# create role policy_role;
> CREATE ROLE
> postgres=# grant select, insert, update, delete on t to policy_role;
> GRANT
> postgres=# alter table t enable row level security;
> ALTER TABLE
> postgres=# create policy t_aLess4 on t for update using (true) with check
> (a
> < 4);
> CREATE POLICY
> postgres=# create policy t_select on t for select using (true);
> CREATE POLICY
> postgres=# set role policy_role;
> SET
> postgres=> select * from t order by a;
>  a
> ---
>  1
>  2
>  3
> (3 rows)
>
> postgres=> insert into t values (1) on conflict (a) do update set a = 0;
> ERROR:  new row violates row-level security policy for table "t"
>

I don’t think this is a bug in RLS, because the RLS system intentionally
validates
whether an INSERT policy exists before performing INSERT … ON CONFLICT
DO UPDATE. With RLS enabled and no INSERT policy defined, postgres
denies the statement before reaching the UPDATE path.

The documentation wording about only applying INSERT policies’ WITH CHECK
expressions to rows “appended by the INSERT path” can be interpreted as
implying
that UPSERT doesn’t require INSERT permissions if the conflict goes to
update,
but in practice postgres enforces INSERT policy presence first.
Clarifying that requirement in the documentation would help future readers
avoid confusion.

-- 
Thanks,
Srinath Reddy Sadipiralla
EDB: https://www.enterprisedb.com/