From: | Jürgen Purtz <juergen(at)purtz(dot)de> |
---|---|
To: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com> |
Cc: | Roger Harkavy <rogerharkavy(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, Michael Paquier <michael(at)paquier(dot)xyz> |
Subject: | Re: Add A Glossary |
Date: | 2020-03-13 04:18:40 |
Message-ID: | 0ba54895-2455-60d7-3244-36030ff2f1e4@purtz.de |
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Lists: | pgsql-docs pgsql-hackers |
> 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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