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{"deleted object would be re-saved by cascade (remove deleted object from associations)[DelftTools.Hydro.HydroNode#2]"} |
Recently
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a
...
lot
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of
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NHibernate
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errors
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have
...
come
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up.
...
A
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very
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common
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cause
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is
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the
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cascade
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rules
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in
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the
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mapping
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as
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they
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require
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close
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attention.
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An
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example
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of
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a
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'wrong'
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mapping
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was
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the
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mapping
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of
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composite
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branch
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structures
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(CS)
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(the
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mapping
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is
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shown
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below).
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The
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CS
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has
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a
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list
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of
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child
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structures
...
and
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these
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were
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persisted
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using
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a
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cascade='all'.
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The
...
same
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structures
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were
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also
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in
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the
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list
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of
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branchfeatures
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on
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the
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branch
...
and
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these
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were
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mapped
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using
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cascade=all-delete-orphan.
...
So
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the
...
same
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weir
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was
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saved
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via
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branch
...
and
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via
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the
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composite
...
structure.
...
This
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is
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fine
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as
...
long
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as
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the
...
cascade
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don't
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conflict.
...
Sometimes
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a
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conflict
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occurs
...
when
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one
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cascade
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results
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in
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a
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delete
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and
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another
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in
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a
...
save.
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For
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example
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a
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compositie
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structure
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is
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deleted
...
and
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the
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cascade
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deletes
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all
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child-structures.
...
But
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one
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of
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these
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structures
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is
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still
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in
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the
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branchfeatures
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collection
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of
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a
...
branch.
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The
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branch
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cascade
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insists
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on
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the
...
object
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being
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saved
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(or
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at
...
least
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not
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deleted)
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and
...
the
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CS
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cascade
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wants
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to
...
delete.
...
Hence
...
a
...
conflict.
...
This
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can
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be
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fixed
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by
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removing
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the
...
structure
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from
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both
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lists
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or
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downgrading/removing
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one
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of
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the
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cascades.
...
In
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this
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case
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the
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branch
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should
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be
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responsible
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for
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saving
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the
...
features
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and
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the
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CS
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should
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have
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a
...
list
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of
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child
...
structures
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without
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cascades.
...
A quick recap of the different cascades :
- none - do not do any cascades, let the users handles them by themselves.
- save-update - when the object is saved/updated, check the associations and save/update any object that require it (including save/update the associations in many-to-many
...
- scenario).
...
- delete - when the object is deleted, delete all the objects in the association.
- delete-orphan - when the object is deleted, delete all the objects in the association. In addition to that, when an object is removed from the association and not associated with another object (orphaned), also delete it. Orphan only checks one relation
- all - when an object is save/update/delete,
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- check
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- the
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- associations
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- and
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- save/update/delete
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- all
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- the
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- objects
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- found.
...
- all-delete-orphan
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- -
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- when
...
- an
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- object
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- is
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- save/update/delete,
...
- check
...
- the
...
- associations
...
- and
...
- save/update/delete
...
- all
...
- the
...
- objects
...
- found.
...
- In
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- additional
...
- to
...
- that,
...
- when
...
- an
...
- object
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- is
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- removed
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- from
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- the
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- association. (orphaned)
...
- delete it. So 're-parenting' (changing parent) is a problem.
A note about orphan cascade:
Orphan only looks at one instance at a time. So a composite structure might have a list of child structures. When a child structure is removed from the CS it is considered an orphan. NHibernate does not care about other relation the structure might have (for example with branch or a new CS)
About reparenting : http://fabiomaulo.blogspot.com/2009/09/nhibernate-tree-re-parenting.html