From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: Debraj Manna <subharaj.manna@gmail.com>,
        pgsql-admin <pgsql-admin@postgresql.org>
Subject: Re: Adding custom constraints on a postgres database
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Comments: In-reply-to "David G. Johnston" <david.g.johnston@gmail.com>
	message dated "Thu, 29 Feb 2024 11:26:27 -0700"
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Date: Thu, 29 Feb 2024 13:35:25 -0500
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"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Thu, Feb 29, 2024, 11:10 Debraj Manna <subharaj.manna@gmail.com> wrote:
>> Can someone let me know if there is a way I can add some custom
>> rules/constraints on a Postgres database?
>> 
>> For example, all tables in a database should have a primary key specified.
>> If someone is trying to violate the rules specified then the SQL command
>> should fail.

> https://www.postgresql.org/docs/current/event-trigger-definition.html

When/where are you expecting to enforce this?  If you prohibit the
common pattern of CREATE TABLE followed sometime later by ALTER TABLE
ADD PRIMARY KEY, you will soon regret that.

I think you might be better served by writing a lint-like thing
that can be run periodically to look through the system catalogs
for policy violations.  Rejecting SQL commands on-the-fly will be
expensive, as well as painful to work with.

			regards, tom lane