hey dan -
nothing sticks out at me based on the code fragments below what might be
going wrong...although you have only provided a fractional portion of your
code (such as, what is AttributeValueAlias? what is
"design_type_attribute"?)
The only way I could have the slightest idea whats going wrong would be to
run it (well, to see the output of the UOW dump also but thats never
enough)....and since I am short on time this week it would be massively
helpful if you could provide a complete working example of the problem,
since otherwise I have to resurrect such an example myself (or if anyone
else on the list thinks they have an idea.)
Keep in mind also that every bona-fide bug tester app goes straight to
becoming a unit test, so you are also contributing code to SA by doing
this.
As it seems like "port hibernate!" is where SA is going, this is fast
approaching the point at which a single core developer/tester is not going
to be enough....
dmiller wrote:
> I'm having a problem with cascading deletes. When deleting a parent
> row SQLAlchemy raises a data integrity error because child rows still
> exist (IntegrityError - update or delete ... violates foreign key
> constraint ...). This seems strange to me since it should be deleting
> the child rows first. I am using the "private=True" flag in my mapper
> relation configuration. I also noticed that the problem disappears
> when I comment out two mapper relationships on the bottom table in my
> hierarchy. This is interesting because those two relationships are
> not mapped with private=True, so they should have no affect on the
> main hierarchy. I have listed my mapper config at the end of this email.
>
> BTW why is the private=... parameter named "private"? Why not call it
> "cascade" since that's a much more familiar/intuitive term. I'd like
> to propose that this parameter be changed to "cascade" and it will
> accept these values:
>
> cascade=None # don't cascade anything (shallow save)
> cascade="orphan" # set child foreign key to null (currently
> private=False)
> cascade="delete" # delete child rows when deleting the parent row
> (currently private=True)
>
> This adds an additional option to ignore cascades on some
> relationships. I think it would fix the problem I described above (I
> would put this option on the two relationships that are causing the
> problem). This option may also even be useful for allowing the
> database to handle cascading deletes (i.e. with ON DELETE CASCADE).
>
> Note: this proposal is still different from Hibernate, which has a
> more complicated cascade mechanism. For example, Hibernates cascade
> mechanism addresses objects in memory as well as database objects.
> Hibernate does not implement persistence by reachability by default.
> This is a difference between Hibernate and SQLAlchemy. I haven't
> decided which I like better yet, so I'm leaving out a few cascade
> options found in Hibernate that have to do with saving/updating
> object graphs. These other options are about how new objects become
> associated with a session (SA automatically associates them with the
> default (thread-local) session, Hibernate does not since it has no
> concept of a default session). If SA switched to handle new objects
> like Hibernate, we could add cascade="insert", which would cause new
> objects associated with a parent to be inserted. At that point we may
> also want to allow a comma-separated value in cascade since some
> people may want cascade="insert,delete" or other combinations. For
> now the options are mutually exclusive.
>
> ~ Daniel
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> # Table defs (abbreviated for clarity)
>
> order = sa.Table("orders", engine,
> sa.Column("id", sa.Integer, sa.Sequence("orders_id_seq"),
> primary_key=True),
> # ...
> )
>
> orderLineItem = sa.Table("order_line_item", engine,
> sa.Column("id", sa.Integer, sa.Sequence("order_line_item_id_seq"),
> primary_key=True),
> sa.Column("order_id", sa.Integer, sa.ForeignKey("orders.id"),
> nullable=False),
> # ...
> )
>
> orderLineItemAttribute = sa.Table("order_line_item_attribute", engine,
> sa.Column("id", sa.Integer, sa.Sequence
> ("order_line_item_attribute_id_seq"), primary_key=True),
> sa.Column("order_line_item_id", sa.Integer, sa.ForeignKey
> ("order_line_item.id"), nullable=False),
> sa.Column("design_type_attribute_id", sa.Integer, sa.ForeignKey
> ("design_type_attribute.id"), nullable=False),
> # ...
> )
>
> orderLineItemAttributeValue = sa.Table
> ("order_line_item_attribute_value", engine,
> sa.Column("id", sa.Integer, sa.Sequence
> ("order_line_item_attribute_value_id_seq"), primary_key=True),
> sa.Column("order_line_item_attribute_id", sa.Integer, sa.ForeignKey
> ("order_line_item_attribute.id"), nullable=False),
> sa.Column("attribute_value_alias_id", sa.Integer, sa.ForeignKey
> ("attribute_value_alias.id")),
> sa.Column("attribute_value_id", sa.Integer, sa.ForeignKey
> ("attribute_value.id")),
> # ...
> )
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> # Mapper defs (abbreviated for clarity)
>
> OrderLineItemAttributeValue.mapper = sa.mapper
> (OrderLineItemAttributeValue, orderLineItemAttributeValue)
>
> OrderLineItemAttribute.mapper = sa.mapper(OrderLineItemAttribute,
> orderLineItemAttribute, properties=dict(
> values=sa.relation(OrderLineItemAttributeValue, private=True,
> backref="attribute"),
> # ...
> ))
>
> OrderLineItem.mapper = sa.mapper(OrderLineItem, orderLineItem,
> properties=dict(
> _attributes=sa.relation(OrderLineItemAttribute, private=True,
> backref="lineItem"),
> # ...
> ))
>
> Order.mapper = sa.mapper(Order, order, properties=dict(
> lineItems=sa.relation(OrderLineItem, private=True, backref="order"),
> ))
>
> # *** NOTE: When i comment out the following two lines the problem
> disappears ***
> OrderLineItemAttributeValue.mapper.add_property
> ("attributeValueAlias", sa.relation(AttributeValueAlias))
> OrderLineItemAttributeValue.mapper.add_property("attributeValue",
> sa.relation(AttributeValue))
>
>
>
>
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