Re: [COMMITTERS] pgsql: Recognize functional dependency on primary keys.

Tom Lane wrote:
> Log Message:
> -----------
> Recognize functional dependency on primary keys. This allows a table's
> other columns to be referenced without listing them in GROUP BY, so long as
> the primary key column(s) are listed in GROUP BY.
>
> Eventually we should also allow functional dependency on a UNIQUE constraint
> when the columns are marked NOT NULL, but that has to wait until NOT NULL
> constraints are represented in pg_constraint, because we need to have
> pg_constraint OIDs for all the conditions needed to ensure functional
> dependency.
>
> Peter Eisentraut, reviewed by Alex Hunsaker and Tom Lane

Because of this commit, I am removing this "we do not want" TODO item:

{{TodoItem
|Indeterminate behavior for the GROUP BY clause (not wanted)
|At least one other database product allows specification of a subset of
the result columns which GROUP BY would need to be able to provide
predictable results; the server is free to return any value from the
group. This is not viewed as a desirable feature.
* [http://archives.postgresql.org/pgsql-hackers/2010-03/msg00297.php
<nowiki>Re: SQL compatibility reminder: MySQL vs PostgreSQL</nowiki>]
}}

My guess is our new 9.1 functionality will reduce requests for this
features, so we can just not list it anymore. If they still ask, we can
re-added this not-wanted item.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +