Thread

Re: Clarification on when _PG_init() is invoked for extensions

Hannu Krosing <hannuk@google.com> — 2025-11-20T21:33:00Z

You probably can do the LOAD in the GUC callback functions and then set
that GUC only for specific databases using ALTER DATABASE SET
<my-extension-loading-guc>=true;

On Thu, Nov 20, 2025 at 6:53 PM Ayush Vatsa <ayushvatsa1810@gmail.com>
wrote:

> Hi,
>
> CREATE extension does not automatically load or ensure that _PG_init() is
>> run.
>> It mainly runs the .sql script in your extension.
>>
> Thanks for the clarification. However, in my testing, _PG_init() did run
> when I executed
> CREATE EXTENSION. I suspect this might be happening because the SQL
> script defines
> C functions using MODULE_PATHNAME, which triggers the library load.
> In a new session, _PG_init() seems to run again when any of those C
> functions are executed.
>
> *My use case:*
> My use case is that I’m building an experimental extension that will be
> installed only in a few
> databases. I want the hooks initialized by this extension to apply only to
> those specific
> databases, while all other databases should continue with the default
> PostgreSQL behavior.
>
> Thank you,
> Ayush
>
>>