On Tue, Apr 15, 2025 at 9:31 AM Adrian Klaver <adrian.kla...@aklaver.com> wrote:
> On 4/15/25 09:21, Igor Korot wrote: > > > > > > > Hi, David, > > > > On Tue, Apr 15, 2025 at 9:56 AM David G. Johnston > > <david.g.johns...@gmail.com <mailto:david.g.johns...@gmail.com>> wrote: > > > > On Tuesday, April 15, 2025, Igor Korot <ikoro...@gmail.com > > <mailto:ikoro...@gmail.com>> wrote: > > > > Hi, ALL, > > Is there a field in the pg_databases table which indicates that > > particular DB is a system one? > > > > > > What is a system database? > > > > > > I consider system database a database that is created by default when > > the server is run for the first time. > > Agreed. > > The fact that initdb creates the template0, template1 and postgres > databases and you can't change that makes them system not user databases. > Based on that definition there is a boundary in the system where OIDs are considered bootstrap/system OIDs versus user OIDs. Key off of that. Though since the names never change, and there are always/only three, it seems pointless to use the OID aspect of initdb as a basis. My definition of a "system database" would be a database that, if it didn't exist, would cause the system to break. i.e., is a database whose presence is integral to the operations of the system. None of these qualify under that definition. Which is why there is no column in pg_database identifying system databases - there are none. The system will continue to operate if you do: initdb createdb newdb psql -c 'alter database template0 is_template false;' dropdb template0 psql -c 'alter database template1 is_template false;' dropdb template1 dropdb --maintenance-db newdb postgres An operational definition worth considering, though, is that any database owned by the bootstrap superuser is a system database. After all, the system owner created/owns them? If you want non-system databases for your application, assign their ownership to a non-system role. David J.
