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Date: Tue, 15 Apr 2025 11:20:08 -0700
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Subject: Re: Fwd: Identify system databases
To: "David G. Johnston" <david.g.johnston@gmail.com>
Cc: Igor Korot <ikorot01@gmail.com>,
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From: Adrian Klaver <adrian.klaver@aklaver.com>
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On 4/15/25 09:48, David G. Johnston wrote:
> On Tue, Apr 15, 2025 at 9:31 AM Adrian Klaver <adrian.klaver@aklaver.com 
> <mailto:adrian.klaver@aklaver.com>> wrote:
> 

> 
>     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.

1) Try connecting(not using single user mode) to a cluster without them.

2) Trying creating a database or databases to replace them without them 
existing in the first place.

If what you say is true why does initdb lack an option to not create 
them on creating a cluster?


> David J.
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com