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

-

1) Implement *uint64* for the flags to provide capacity for up to 64
distinct options.
2) Refactor parse_ddl_options to return the flag set directly rather than
using an *out parameter*.

Please find the attached *v7* patch, which is now ready for review.

On Wed, Jan 14, 2026 at 9:18 PM Akshay Joshi <akshay(dot)joshi(at)enterprisedb(dot)com>
wrote:

> I have incorporated Euler’s changes, which modify the declaration and
> definition of the *pg_get_database_ddl* function. Please find the
> attached v6 patch, which is now ready for review. The following updates
> have been made:
>
> 1.
>
> Function signature updated to: pg_get_database_ddl(database_id
> regdatabase, VARIADIC ddl_options text[])
> 2.
>
> Added options *--no-owner* and *--no-tablespace* to omit the OWNER and
> TABLESPACE clauses from the reconstructed DDL.
> 3.
>
> Moved the "*pretty*" parameter into ddl_options for formatted output.
> 4.
>
> Properties such as ENCODING, LOCALE_PROVIDER, TABLESPACE, CONNECTION
> LIMIT, and ALLOW_CONNECTIONS are omitted if they are set to default values.
> 5.
>
> Introduced the *--with-defaults* option to include clauses for
> parameters even when they are at their default values.
> 6.
>
> Standardized formatting to use spaces instead of tabs.
>
> *Usage examples:*
>
> 1. SELECT pg_get_database_ddl('postgres'); // Non pretty-formatted DDL
> 2. SELECT pg_get_database_ddl(16835); // Non pretty-formatted DDL
> 3. SELECT pg_get_database_ddl('postgres', 'pretty'); //
> pretty-formatted DDL
> 4. SELECT pg_get_database_ddl('postgres', '--no-owner',
> '--no-tablespace'); // Omits the Owner and Tablespace clause from the DDL.
> 5. SELECT pg_get_database_ddl('postgres', 'pretty',
> '--with-defaults'); // Includes clauses for parameters that are currently
> at their default values.
>
>
> On Thu, Jan 8, 2026 at 4:57 AM Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:
>
>>
>> On 2025-12-12 Fr 10:19 AM, Euler Taveira wrote:
>>
>> On Fri, Dec 12, 2025, at 7:52 AM, Akshay Joshi wrote:
>>
>> On Thu, Dec 11, 2025 at 7:29 PM Euler Taveira <euler(at)eulerto(dot)com> <euler(at)eulerto(dot)com> wrote:
>>
>> Is there any way to obtain the default values directly from the source
>> code itself, or do I need to refer to the documentation? If we rely on
>> the documentation and compare against that, then in the future, if the
>> default values change, we would also need to update our logic
>> accordingly.
>>
>>
>> No, you need to check the documentation. If you are changing the default value,
>> you are breaking compatibility; that rarely happens. If we are really concern
>> about this fact, you can add a test case that creates the object without
>> properties (all default values) and another with all default properties and
>> then compare the output.
>>
>>
>> Maybe the function should have a VERBOSE option that emits all the
>> defaults.
>>
>>
>> Constantly having to check the documentation for default values may
>> feel annoying to some users. Some users run queries with parameters
>> such as encoding, connection limit, and locale using their default
>> values. When they call the pg_get_database_ddl function, it
>> reconstructs the short command based on those defaults.
>>
>>
>> Encoding and locale, ok but I doubt about connection limit.
>>
>> postgres=# SELECT current_user;
>> current_user
>> --------------
>> euler
>> (1 row)
>>
>> postgres=# CREATE DATABASE foo;
>> CREATE DATABASE
>> postgres=# CREATE DATABASE bar OWNER euler;
>> CREATE DATABASE
>>
>> When you are learning a new command, you generally don't set the default value
>> for a property just to be correct. I'm not saying this function shouldn't
>> include OWNER. I'm just suggesting it to be optional. See some arguments
>> below.
>>
>>
>> * OWNER. There is no guarantee that the owner exists in the cluster you will
>> use this output. That's something that pg_dumpall treats separately (see
>> above). Does it mean we should include the owner? No. We can make it an
>> option.
>>
>>
>> If I understand correctly, the owner should be an option provided by
>> the caller of the function, and we reconstruct the Database DDL using
>> that specified owner. Is that right?
>> If so, then in my humble opinion, this is not truly a reconstruction
>> of the existing database object.
>>
>>
>> No. My idea is to have something like the pg_dump --no-owner option. This is
>> important if you are transporting the objects from one cluster to another one.
>> Owner might be different. That's why I'm suggesting it should be optional. It
>> means flexibility. See pg_dump output format that always apply the OWNER as a
>> separate ALTER command.
>>
>>
>> +1
>>
>>
>> * options. Since I mentioned options for some properties (owner, strategy,
>> template), these properties can be accommodated as a VARIADIC argument. The
>> function signature can be something like
>>
>> pg_get_database_ddl(oid, VARIADIC options text[])
>>
>> I would include the pretty print into options too.
>>
>>
>> Same comment as the one I gave for the Owner, if you are referring to
>> these as options to the function.
>>
>>
>> Let me elaborate a bit. As I suggested you can control the output with options.
>> Why? Flexibility.
>>
>> Why am I suggesting such a general purpose implementation? See some of the use
>> cases.
>>
>> 1. object DDL. Check DDL to recreate the object. It is not the exact DDL that
>> the user informed but it produces the same result.
>> 2. clone tool. Clone the objects to recreate the environment for another
>> customer. These objects can be created in the same cluster or in another one.
>> (Of course, global objects don't apply for the same cluster.)
>> 3. dump tool. Dump the commands to recreate the existing objects.
>> 4. diff tool. There are tools like pgquarrel [1] that queries the catalog and
>> compare the results to create commands to turn the target database into the
>> source database. The general purpose functions can be used if the object
>> doesn't exist in the target database. (Of course, it doesn't apply for global
>> objects but again it is a good UI to have all of these pg_get_OBJECT_ddl
>> functions using the same approach.)
>> 5. logical replication. These pg_get_OBJECT_ddl functions can be good
>> candidates to be used in the initial schema replication and even in the DDL
>> replication (if the object doesn't exist in the target database).
>>
>> The "options" parameter is to get the DDL command to serve any of these use
>> cases. There are some properties in a certain object that you *don't* want for
>> whatever reason. See some --no-OBJECT options in pg_dump. Let's say you don't
>> want the TABLESPACE or the table access method while getting the CREATE TABLE
>> DDL because it is different in the other database.
>>
>>
>> +1
>>
>>
>> I received a review comment suggesting the use of tabs. I also looked
>> up PostgreSQL best practices on google, which recommend using tabs for
>> indentation and spaces for alignment. I’m open to updating my code
>> accordingly.
>>
>>
>> I didn't check all of the possible output but the majority uses space instead
>> of tabs. Check psql. If you check the git history (git log --grep=tabs), you
>> will notice that tabs are removed from source code.
>>
>>
>>
>> We should follow the pretty printing style in ruleutils.c, which uses
>> spaces.
>>
>>
>> * permission. I don't think you need to check for permissions inside the
>> function. I wouldn't want a different behavior than pg_dump(all). You can
>> always adjust it in system_functions.sql.
>>
>>
>> We’ve already had extensive discussions on this topic in the same
>> email thread, and ultimately we decided to add the permission check.
>>
>>
>> That's fair. Again, I expect that all of these pg_get_OBJECT_ddl functions use
>> the same approach. We can always relax this restriction in the future.
>>
>>
>>
>> +1
>>
>>
>> cheers
>>
>>
>> andrew
>>
>> --
>> Andrew Dunstan
>> EDB: https://www.enterprisedb.com
>>
>>