Re: [PATCH] Add pg_get_policy_ddl() function to reconstruct CREATE POLICY statement

Rebased *v13* patch is now ready for review and commit.

On Mon, Jun 22, 2026 at 6:49 PM Akshay Joshi <akshay(dot)joshi(at)enterprisedb(dot)com>
wrote:

> *Chao Li* found an issue in my other patch for *pg_get_table_ddl.* Specifically,
> the existing pattern in pg_proc.dat for variadic-text functions (e.g.,
> jsonb_delete, json_extract_path) uses *_text* instead of *text* at the
> variadic position in both proargtypes and proallargtypes, with provariadic
> => 'text'. This is the convention documented by the sanity check in
> src/test/regress/sql/opr_sanity.sql.
>
> I realized the same issue was present in this patch as well, so I have
> fixed it and added corresponding test cases.
>
> The v12 patch is now ready for review and commit.
>
> On Mon, Jun 22, 2026 at 6:34 PM Akshay Joshi <
> akshay(dot)joshi(at)enterprisedb(dot)com> wrote:
>
>>
>>
>> On Mon, Jun 8, 2026 at 6:10 PM solai v <solai(dot)cdac(at)gmail(dot)com> wrote:
>>
>>> Hi all,
>>>
>>>
>>> On Mon, Jun 8, 2026 at 5:32 PM Japin Li <japinli(at)hotmail(dot)com> wrote:
>>> >
>>> > On Fri, 29 May 2026 at 12:20, Akshay Joshi <
>>> akshay(dot)joshi(at)enterprisedb(dot)com> wrote:
>>> > > Thanks for the reviews.
>>> > >
>>> > > My original patch (v9) was actually correct. After considering
>>> Japin's review comment, I initially thought the extra
>>> > > parentheses weren't necessary, but they are indeed required for
>>> handling boolean values properly in non-pretty mode too,
>>> > > so I kept them in USING (%s) / WITH CHECK (%s) for both modes.
>>> > >
>>> >
>>> > My bad! I had not considered this situation.
>>> >
>>> > > `pg_get_expr()` only adds outer parentheses for composite
>>> expressions (via the deparsers for `OpExpr`, `BoolExpr`, etc.).
>>> > > For atomic top-level nodes like `Const`, `Var`, `current_user`,
>>> `NULL`, etc.
>>> > > For example:
>>> > >
>>> > > CREATE POLICY p ON t USING (true);
>>> > > SELECT pg_get_policy_ddl('t', 'p'); -- previously: ... USING
>>> true; (syntax error)
>>> > >
>>> > > This is exactly why `pg_dump` always wraps the expression
>>> unconditionally; see `src/bin/pg_dump/pg_dump.c`:4473-4477:
>>> > >
>>> > > if (polinfo->polqual != NULL)
>>> > > appendPQExpBuffer(query, " USING (%s)", polinfo->polqual);
>>> > > if (polinfo->polwithcheck != NULL)
>>> > > appendPQExpBuffer(query, " WITH CHECK (%s)",
>>> polinfo->polwithcheck);
>>> > >
>>> > > I've also added a round-trip regression test with `USING (true)` /
>>> `WITH CHECK (false)` that captures the generated DDL,
>>> > > drops the policies, re-executes the DDL, and verifies the policies
>>> are recreated.
>>> > >
>>> > > v11 Patch attached for review.
>>> > >
>>> > > On Thu, May 28, 2026 at 7:12 PM Ilmar Y <tanswis42(at)gmail(dot)com> wrote:
>>> > >
>>> > > The following review has been posted through the commitfest
>>> application:
>>> > > make installcheck-world: not tested
>>> > > Implements feature: tested, failed
>>> > > Spec compliant: not tested
>>> > > Documentation: not tested
>>> > >
>>> > > Hi,
>>> > >
>>> > > I looked at v10, focused on whether the generated CREATE POLICY
>>> statement
>>> > > can be executed again.
>>> > >
>>> > > The patch applies cleanly on current master at
>>> > > 8a86aa313a714adc56c74e4b08793e4e6102b5ca.
>>> > >
>>> > > git diff --check reports no issues.
>>> > >
>>> > > I built with:
>>> > >
>>> > > ./configure --prefix="$PWD/pg-install" --without-readline
>>> --without-zlib --without-icu
>>> > > make -s -j8
>>> > > make -s install
>>> > >
>>> > > make -C src/test/regress check TESTS=rowsecurity
>>> > >
>>> > > ended up running the full parallel_schedule in this makefile; all
>>> 245 tests
>>> > > passed, including rowsecurity.
>>> > >
>>> > > I found one correctness issue in the generated non-pretty DDL. The
>>> code
>>> > > assumes that pg_get_expr_ext(..., false) already returns the
>>> parentheses
>>> > > required by CREATE POLICY syntax, but that is not true for simple
>>> boolean
>>> > > constants.
>>> > >
>>> > > For example:
>>> > >
>>> > > CREATE TABLE t(a int);
>>> > > CREATE POLICY p_true ON t USING (true);
>>> > > SELECT ddl FROM pg_get_policy_ddl('t', 'p_true', 'pretty', 'false')
>>> AS ddl;
>>> > >
>>> > > returns:
>>> > >
>>> > > CREATE POLICY p_true ON public.t USING true;
>>> > >
>>> > > If I drop the policy and execute that generated statement, it fails:
>>> > >
>>> > > ERROR: syntax error at or near "true"
>>> > > LINE 1: CREATE POLICY p_true ON public.t USING true;
>>> > > ^
>>> > >
>>> > > The same issue reproduces for WITH CHECK:
>>> > >
>>> > > CREATE POLICY p_check ON t FOR INSERT WITH CHECK (false);
>>> > >
>>> > > is reconstructed as:
>>> > >
>>> > > CREATE POLICY p_check ON public.t FOR INSERT WITH CHECK false;
>>> > >
>>> > > and executing it fails at "false".
>>> > >
>>> > > So I think USING and WITH CHECK need to be parenthesized in
>>> non-pretty mode
>>> > > too, or the tests should include a round-trip execution check for
>>> generated
>>> > > DDL with simple boolean expressions.
>>> > >
>>> > > I used two small SQL reproducers for the manual checks; the
>>> complete repro is
>>> > > included above.
>>> > >
>>> > > I have not reviewed the broader pg_get_*_ddl API design or every
>>> possible
>>> > > policy expression form.
>>> > >
>>> > > Regards,
>>> > > Ilmar Yunusov
>>> > >
>>> > > The new status of this patch is: Waiting on Author
>>> >
>>>
>>>
>>> I reviewed and tested the V11 pg_get_policy_ddl() patch. I verified
>>> the basic functionality by creating various row-level security
>>> policies and checking the reconstructed DDL returned by
>>> pg_get_policy_ddl(). The function correctly reconstructed policies for
>>> different command types (SELECT, INSERT, UPDATE, DELETE), PERMISSIVE
>>> and RESTRICTIVE policies, multiple role lists, quoted identifiers,
>>> USING clauses, and WITH CHECK clauses.
>>> I also tested more complex cases involving subqueries. Policies
>>> containing EXISTS subqueries in both USING and WITH CHECK clauses were
>>> reconstructed successfully. Nested subqueries were also handled
>>> correctly, and I did not encounter any issues related to expression
>>> reconstruction or variable handling. I verified NULL input handling as
>>> well. Passing NULL values for the table name or policy name returned
>>> no rows as expected. Invalid relation names resulted in the expected
>>> regclass resolution error. One observation from testing is that the
>>> generated DDL omits default clauses such as FOR ALL and TO PUBLIC. For
>>> example, a policy created with FOR ALL TO PUBLIC is reconstructed
>>> without those clauses, while still producing semantically equivalent
>>> DDL. I'm not sure whether this is intentional or if the function is
>>> expected to reproduce all clauses explicitly, but it may be worth
>>> discussing.
>>> Overall, the patch worked as expected in all scenarios I tested, and I
>>> did not find any functional issues.
>>>
>>
>> Thanks for the review. The omission of FOR ALL and TO PUBLIC is
>> intentional and matches the long-standing convention used by
>> pg_get_indexdef, pg_get_constraintdef, pg_get_viewdef, etc.: emit a clause
>> only when it differs from the parser's default. The result is semantically
>> equivalent to the CREATE POLICY DDL.
>>
>>>
>>>
>>> Regards,
>>> Solai
>>>
>>