Re: [PATCH] Add pg_get_database_ddl() function to reconstruct CREATE DATABASE statement

On Thu, Nov 13, 2025 at 10:18 AM Quan Zongliang <quanzongliang(at)yeah(dot)net>
wrote:

>
>
> On 11/13/25 12:17 PM, Quan Zongliang wrote:
> >
> >
> > On 11/12/25 8:04 PM, Akshay Joshi wrote:
> >> Hi Hackers,
> >>
> >> I’m submitting a patch as part of the broader Retail DDL Functions
> >> project described by Andrew Dunstan https://www.postgresql.org/
> >> message- id/945db7c5-be75-45bf-b55b-cb1e56f2e3e9%40dunslane.net
> >> <https:// www.postgresql.org/message-id/945db7c5-be75-45bf-b55b-
> >> cb1e56f2e3e9%40dunslane.net>
> >>
> >> This patch adds a new system function
> >> pg_get_database_ddl(database_name/ database_oid, pretty), which
> >> reconstructs the CREATE DATABASE statement for a given database name
> >> or database oid. When the pretty flag is set to true, the function
> >> returns a neatly formatted, multi-line DDL statement instead of a
> >> single-line statement.
> >>
> >> *Usage examples:*
> >>
> >> 1) SELECT pg_get_database_ddl('test_get_database_ddl_builtin'); --
> >> *non-pretty formatted DDL*
> >> pg_get_database_ddl
> >>
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >> CREATE DATABASE test_get_database_ddl_builtin WITH OWNER =
> >> regress_ddl_database ENCODING = "UTF8" LC_COLLATE = "C" LC_CTYPE = "C"
> >> BUILTIN_LOCALE = "C.UTF-8" COLLATION_VERSION = "1" LOCALE_PROVIDER =
> >> 'builtin' TABLESPACE = pg_default ALLOW_CONNECTIONS = true CONNECTION
> >> LIMIT = -1;
> >>
> >>
> >> 2) SELECT pg_get_database_ddl('test_get_database_ddl_builtin', true);
> >> -- *pretty formatted DDL*
> >>
> >> CREATE DATABASE test_get_database_ddl_builtin
> >> WITH
> >> OWNER = regress_ddl_database
> >> ENCODING = "UTF8"
> >> LC_COLLATE = "C"
> >> LC_CTYPE = "C"
> >> BUILTIN_LOCALE = "C.UTF-8"
> >> COLLATION_VERSION = "1"
> >> LOCALE_PROVIDER = 'builtin'
> >> TABLESPACE = pg_default
> >> ALLOW_CONNECTIONS = true
> >> CONNECTION LIMIT = -1;
> >>
> >> 3) SELECT pg_get_database_ddl(16835); -- *non-pretty formatted
> >> DDL for OID*
> >> 4) SELECT pg_get_database_ddl(16835, true); -- *pretty formatted DDL
> >> for OID*
> >>
> >> The patch includes documentation, in-code comments, and regression
> >> tests, all of which pass successfully.
> >> *
> >> **Note:* To run the regression tests, particularly the pg_upgrade
> >> tests successfully, I had to add a helper function, ddl_filter (in
> >> database.sql), which removes locale and collation-related information
> >> from the pg_get_database_ddl output.
> >>
> > I think we should check the connection permissions here. Otherwise:
> >
> > postgres=> SELECT pg_database_size('testdb');
> > ERROR: permission denied for database testdb
> > postgres=> SELECT pg_get_database_ddl('testdb');
> >
> > pg_get_database_ddl
> >
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> > CREATE DATABASE testdb WITH OWNER = quanzl ENCODING = "UTF8"
> > LC_COLLATE = "zh_CN.UTF-8" LC_CTYPE = "zh_CN.UTF-8" LOCALE_PROVIDER =
> > 'libc' TABLESPACE = pg_default ALLOW_CONNECTIONS = true CONNECTION LIMIT
> > = -1;
> > (1 row)
> >
> > Users without connection permissions should not generate DDL.
> >
>
> The "dbOwner" is defined as a null pointer.
> char *dbOwner = NULL;
>
> Later, there might be a risk of it not being assigned a value.
> if (OidIsValid(dbForm->datdba))
> dbOwner = GetUserNameFromId(dbForm->datdba, false);
>
> Although there is no problem in normal circumstances here. Many parts of
> the existing code have not been checked either. Since this possibility
> exists, it should be checked before using it. Just like the function
> roles_is_member_of (acl.c).
>
> if (dbOwner)
> get_formatted_string(&buf, prettyFlags, 1, "OWNER = %s",
> quote_identifier(dbOwner));
>

Fixed the given review comment. I've attached the v2 patch ready for
review.

>
> > Regards,
> > Quan Zongliang
> >
> >> -----
> >> Regards,
> >> Akshay Joshi
> >> EDB (EnterpriseDB)
> >>
> >>
> >>
> >
> >
>
>