OK this issue is actually limited to "transient" objects only; that
is, if you had flushed your session before doing the merge() it would
have worked. The fix is in r4104. Im considering putting out 0.4.3
today as a mostly bugfix release but have not decided yet.
On Jan 30, 2008, at 6:14 AM, Paul-Michael Agapow wrote:
>
> I'm using merge to push objects into a db. (Long story short: I have
> a set of objects that have to behave identically if they are
> persisted or not, and may be retrieved or sent to a set of
> databases. Hence the use of merge.) However, merged objects appear
> object joined by a relation and backrefs twice. Is this a bug or an
> I making some subtle mistake?
>
> A condensed demonstration - the names of the mapped objects and
> tables are unimportant, but a Biosequence has a one-to-many with a
> set of Annotations, established by a backref::
>
> from sqlalchemy import *
> from sqlalchemy.orm import *
>
> metadata = MetaData()
>
> class Biosequence (object):
> pass
>
> class Annotation (object):
> pass
>
> table_biosequences = Table ('biosequences', metadata,
> Column ('identifier', Integer(), primary_key=True),
> Column ('dummy', String(16)),
> )
>
> table_seqannotations = Table ('seqannotations', metadata,
> Column ('identifier', Integer(), primary_key=True),
> Column ('biosequence_id', Integer(), ForeignKey
> ('biosequences.identifier')),
> )
>
> mapper (Annotation, table_seqannotations)
> mapper (Biosequence, table_biosequences,
> properties={
> 'annotations':relation (
> Annotation,
> backref='biosequence_ref',
> lazy=False,
> cascade="all, delete, delete-orphan",
> ),
> },
> )
>
> engine = create_engine ('sqlite:///', convert_unicode=True,
> # echo=True,
> )
> sessionfactory = sessionmaker (bind=engine, autoflush=False,
> transactional=False)
> session = sessionfactory()
> metadata.create_all (bind=engine, checkfirst=True)
>
> # make an object with 3 'children'
> bseq = Biosequence()
> anns = [Annotation() for x in range (3)]
> bseq.annotations = anns
> print "Original num of anns:", len (bseq.annotations)
>
> # the merged copy has 6 children
> merge_bseq = session.merge (bseq)
> session.flush()
> print "Now num of anns still:", len (bseq.annotations)
> print "Ids:", [x.identifier for x in bseq.annotations]
> print "Merged copy num of anns:", len (merge_bseq.annotations)
> print "Ids:", [x.identifier for x in merge_bseq.annotations]
>
> # as does the return!
> results = session.query (Biosequence)
> print "Number of results", results.count()
> returned_bseq = results.one()
> print "Returned num of anns:", len (returned_bseq.annotations)
> print "Ids:", [x.identifier for x in returned_bseq.annotations]
>
> # make an new object with 3 children
> bseq2 = Biosequence()
> bseq2.annotations = [Annotation() for x in range (3)]
> print "New obj num of anns:", len (bseq.annotations)
> session.save_or_update (bseq2)
> session.flush()
>
> # and it works as expected
> results = session.query (Biosequence)
> print "Number of retreived objects", results.count()
> returned_bseqs = results.all()
> for item in returned_bseqs:
> print "Returned num of anns:", len (item.annotations)
> print "Ids:", [x.identifier for x in item.annotations]
>
>
> Which returns::
>
> Original num of anns: 3
> Now num of anns still: 3
> Ids: [None, None, None]
> Merged copy num of anns: 6
> Ids: [1, 1, 2, 2, 3, 3]
> Number of results 1
> Returned num of anns: 6
> Ids: [1, 1, 2, 2, 3, 3]
> New obj num of anns: 3
> Number of retreived objects 2
> Returned num of anns: 6
> Ids: [1, 1, 2, 2, 3, 3]
> Returned num of anns: 3
> Ids: [4, 5, 6]
>
> In summary: if an object is stored using 'save_or_update', when
> later retrieved, it has the correct number of related children. If
> merged, the returned merge copy has each child twice. If this object
> is retrieved later, it still has every child twice. Looking at the
> db, the correct number of child rows is being stored and the
> relations are correct. It therefore looks like there's a problem in
> the session for merged objects.
>
> Any pointers?
>
> --
> Dr Paul-Michael Agapow: VieDigitale / Inst. for Animal Health
> [EMAIL PROTECTED] / [EMAIL PROTECTED]
>
>
>
>
> >
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