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
specificationof a subset ofthe result columns which GROUP BY would need to be able to providepredictable results; the
serveris free to return any value from thegroup. 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@momjian.us> http://momjian.us EnterpriseDB
http://enterprisedb.com
+ It's impossible for everything to be true. +