[orm-devel] many2many extension

[Mike Watkins]

Please ignore my last comment, clearly I should not read backwards.

Mike

At 03:57 PM 11/27/2002 -0600, you wrote:
>Hey all -
>I'm playing with ORM a bit, to see how it might fit into our Postgresql/Zope
>setup. One thing I'm looking at is the many2many relationship. As written,
>it has a builtin assumption: that your 'matrixtable' (I usually
>call this a linking table) hold the primary keys of the two linked tables.
>
>In my case, we've got a structure where we're grouping together collections
>of people, and reusing the groupings, where possible. Here's an example:
>
>     modules (moduleid serial,
>              name text,
>              version int,
>              authorgroupid int,
>              maintainergroupid int)
>
>     persons (personid serial,
>             name text,
>             login text)
>
>     groups (groupid int,
>             personid int)
>
>In this case, we've two different many2many relationships between modules
>and people: authors, and maintainers. Since we have many modules, and
>many authors, to optimize storage space we reuse a groupids, when we can
>(same set of people)
>
>So, to retrieve all the authors for a given module (1234), it would be
>something like:
>
>SELECT name from modules, persons, groups where moduleid=1234 and
>authorgroupid=groupid and groups.personid = persons.personid
>
>For ORM, this means modifying the many2many class to take another
>parameter (I've called it myKey) which is the SQL column name in the
>parent table that hold the key that is stored in the matrix table.
>
>So, here's my problem: how do I tweak ORM to retrieve this column type?
>It's basically a many2many, but I need to retrieve the 'myKey' column
>when the parent table tuples are pulled, and then us that value when
>the child tuples are pulled.
>
>The last part is here: (relationships.many2manyColumn._init_, ~ line 540)
>
>existing code says:
>
>             where = "%s.%s = %s AND %s.%s = %s.%s " % \
>                     (self._column.matrixTable(),
>                      self._column.myColumn(),
>                      self._column.dbObj().primaryKeyValue().format(),
>                      self._column.matrixTable(),
>                      self._column.childsColumn(),
>                      self._column.childClass().relation(),
>                      self._column.dbObj().primaryKey)
>
>There's a bug here, BTW: the last line should be (it's slipped through
>because all your primaryKeys are named 'id'):
>
>                      self._column.childClass().primaryKey)
>
>
>I need something like:
>
>            where = "%s.%s = %s AND %s.%s = %s.%s " % \
>                     (self._column.matrixTable(),
>                      self._column.myColumn(),
>                      self._column.myKey(), #FIXME need _value_ of myKey
>                      self._column.matrixTable(),
>                      self._column.childsColumn(),
>                      self._column.childClass().relation(),
>                      self._column.childClass().primaryKey)
>
>
>Any suggestions?
>
>Ross
>--
>Ross Reedstrom, Ph.D.                                 reedstrm@rice.edu
>Executive Director                                  phone: 713-348-6166
>Gulf Coast Consortium for Bioinformatics              fax: 713-348-6182
>Rice University MS-39
>Houston, TX 77005
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