Feedback-ID: ia2694551:Fastmail
Date: Tue, 10 Oct 2023 17:15:36 +0200
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Esteban Zimanyi <estebanzimanyi@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Fwd: Advice about preloaded libraries
Message-ID: <202310101515.ucdlddy5xmxp@alvherre.pgsql>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <CAPqRbE7m3+tDCg08e-5xLXW0aUvaadNvfvXMmupS2_jr_jLCFQ@mail.gmail.com>
Archived-At: <https://www.postgresql.org/message-id/202310101515.ucdlddy5xmxp%40alvherre.pgsql>
Precedence: bulk

On 2023-Oct-10, Esteban Zimanyi wrote:

> As can be seen above, it is not REALLY mandatory to have
> shared_preload_libraries = 'postgis-3' but then the user is responsible for
> issuing a query to load PostGIS (select st_point(1,1); above) and then she
> is able to execute MobilityDB queries.

Calling a function that exists in some library will cause the library to
be loaded.  Alternatively, you can cause the library to be loaded
automatically at some point of the start sequence, by
shared_preload_libraries or the other configuration options.  Or you can
use the LOAD statement.

If by whichever mechanism postgis has been loaded into your session,
then calling a function in MobilityDB will work fine, because the
postgis library will have been loaded.  It doesn't matter exactly how
was postgis loaded.

The advantage of using shared_preload_libraries is performance of
connection establishment: the library is loaded by the postmaster, so
each new backend inherits it already loaded and doesn't have to load it
itself.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"I love the Postgres community. It's all about doing things _properly_. :-)"
(David Garamond)