[Modeling-users] Fetching relationships in batch

[Sebastien B. <sbi...@us...>]

        Hi,

  Given the recent discussion we had w/ Yannick on to-many faults being
  triggered even when all te related objects were previously fetched,
  here is a first implementation of
  DatabaseContext.batchFetchRelationship()

  You'll find the patch at:
https://sourceforge.net/tracker/index.php?func=3Ddetail&aid=3D771009&group_=
id=3D58935&atid=3D489337

  While it's quite naive for the moment being, it is completely usable.

  Current limitations: it can only acts on to-many relationships, and
  these to-many rels should have an inverse to-one relationship.

Usage (this is NOT the definitive API that will be exposed to users ;)
-----

Say you have Company.toPersons <---->> Person.company

  1. fetch the companies you want,
  2. use this:

>>> from Modeling.ModelSet import defaultModelSet
>>> dbContext=3DdatabaseContext('Company', ec)
>>> rel=3DdefaultModelSet().entityNamed('Company').relationshipNamed('perso=
ns')
>>> dbContext.batchFetchRelationship(rel, companies, ec)

  given that databaseContext() is:

    def databaseContext(entityName, ec):
       from Modeling.FetchSpecification import FetchSpecification
       fs=3DFetchSpecification(entityName)
       return ec.rootObjectStore().objectStoreForFetchSpecification(fs)

  With this you'll get only 2 fetches: one for the master (companies),
  one for the slaves (related persons).

    Yannick, could you try this and report please?

-- S=E9bastien.