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From: Jürgen Purtz <[email protected]>
To: Corey Huinker <[email protected]>
Cc: Roger Harkavy <[email protected]>
Cc: [email protected]
Cc: Fabien COELHO <[email protected]>
Cc: Michael Paquier <[email protected]>
Subject: Re: Add A Glossary
Date: Fri, 13 Mar 2020 10:18:40 +0600
Message-ID: <[email protected]> (raw)
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> The statement that names of schema objects are unique isn't 
> /strictly/ true, just /mostly/ true. Take the case of a unique 
> constraints. 

Concerning CONSTRAINTS you are right. Constraints seems to be an exception:

  * Their name belongs to a schema, but are not necessarily unique
    within this context:
    https://www.postgresql.org/docs/current/catalog-pg-constraint.html.
  * There is a UNIQUE index within the system catalog pg_constraints:
    "pg_constraint_conrelid_contypid_conname_index" UNIQUE, btree
    (conrelid, contypid, conname), which expresses that names are unique
    within the context of a table/constraint-type. Nevertheless tests
    have shown that some stronger restrictions exists across
    table-boarders (,which seems to be implemented in CREATE statements
    - or as a consequence of your mentioned correlation between
    constraint and index ?).

I hope that there are no more such exception to the global rule 'object 
names in a schema are unique': 
https://www.postgresql.org/docs/current/sql-createschema.html

This facts must be mentioned as a short note in glossary and in more 
detail in the later patch about the architecture.

J. Purtz

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