Re: Fwd: Identify system databases

On Tue, Apr 15, 2025 at 3:11 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> "David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> > On Tue, Apr 15, 2025 at 11:20 AM Adrian Klaver <
> adrian(dot)klaver(at)aklaver(dot)com>
> > wrote:
> >> If what you say is true why does initdb lack an option to not create
> >> them on creating a cluster?
>
> > By creating the initial three databases the system is more usable due to
> > having established conventions. They are conventional databases, not
> > system ones.
>
> Precisely. For example, the only reason for the "postgres" database
> to exist is so that there is a reasonable default database for clients
> to connect to. If we didn't have it we'd need some other convention.
> (Indeed, we used to not have it, and back then the default client
> behavior was usually to connect to template1. That led to people
> creating random junk in template1 and then being surprised when
> CREATE DATABASE copied it into new databases.)
>

Interesting history. I've always interpreted the "postgres" database as
being the system database, but now I know it's not.

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