Re: [Sqlalchemy-tickets] [sqlalchemy] #2921: backref relationships with cascade delete-orphan throw IntegrityError when child is replaced

[sqlalchemy <mi...@zz...>]

#2921: backref relationships with cascade delete-orphan throw IntegrityError when
child is replaced
------------------------------+----------------------------------
      Reporter:  elmer        |      Owner:  zzzeek
          Type:  defect       |     Status:  new
      Priority:  high         |  Milestone:  0.9.xx
     Component:  orm          |   Severity:  minor - half an hour
    Resolution:               |   Keywords:
Progress State:  needs tests  |
------------------------------+----------------------------------
Changes (by zzzeek):

 * priority:  medium => high
 * status_field:  awaiting triage => needs tests
 * component:  (none) => orm
 * severity:  no triage selected yet => minor - half an hour
 * milestone:   => 0.9.xx


Comment:

 Here's a patch that would the be the ORM's first foray into disabling
 autoflush at certain places.  Typically I never want to do this, but as
 this is in the middle of attribute state being modified it might be
 appropriate; but mostly making the case easy here is that all tests
 continue to pass.  i might be able to make this for 0.9.2.

 {{{
 #!diff
 diff --git a/lib/sqlalchemy/orm/attributes.py
 b/lib/sqlalchemy/orm/attributes.py
 index e5f8550..08156a6 100644
 --- a/lib/sqlalchemy/orm/attributes.py
 +++ b/lib/sqlalchemy/orm/attributes.py
 @@ -23,7 +23,7 @@ from .base import PASSIVE_NO_RESULT, ATTR_WAS_SET,
 ATTR_EMPTY, NO_VALUE,\
              NEVER_SET, NO_CHANGE, CALLABLES_OK, SQL_OK,
 RELATED_OBJECT_OK,\
              INIT_OK, NON_PERSISTENT_OK, LOAD_AGAINST_COMMITTED,
 PASSIVE_OFF,\
              PASSIVE_RETURN_NEVER_SET, PASSIVE_NO_INITIALIZE,
 PASSIVE_NO_FETCH,\
 -            PASSIVE_NO_FETCH_RELATED, PASSIVE_ONLY_PERSISTENT
 +            PASSIVE_NO_FETCH_RELATED, PASSIVE_ONLY_PERSISTENT,
 NO_AUTOFLUSH
  from .base import state_str, instance_str

  @inspection._self_inspects
 @@ -761,7 +761,8 @@ class ScalarObjectAttributeImpl(ScalarAttributeImpl):

          """
          if self.dispatch._active_history:
 -            old = self.get(state, dict_, passive=PASSIVE_ONLY_PERSISTENT)
 +            old = self.get(state, dict_, passive=PASSIVE_ONLY_PERSISTENT
 +                                                    | NO_AUTOFLUSH)
          else:
              old = self.get(state, dict_, passive=PASSIVE_NO_FETCH)

 diff --git a/lib/sqlalchemy/orm/base.py b/lib/sqlalchemy/orm/base.py
 index 577f9ff..b13396e 100644
 --- a/lib/sqlalchemy/orm/base.py
 +++ b/lib/sqlalchemy/orm/base.py
 @@ -80,6 +80,13 @@ LOAD_AGAINST_COMMITTED =
 util.symbol("LOAD_AGAINST_COMMITTED",
  """, canonical=32
  )

 +NO_AUTOFLUSH = util.symbol("NO_AUTOFLUSH",
 +"""loader callables should disable autoflush.
 +
 +.. versionadded:: 0.9.2
 +
 +""", canonical=64)
 +
  # pre-packaged sets of flags used as inputs
  PASSIVE_OFF = util.symbol("PASSIVE_OFF",
      "Callables can be emitted in all cases.",
 diff --git a/lib/sqlalchemy/orm/strategies.py
 b/lib/sqlalchemy/orm/strategies.py
 index bd9b02d..14c2cf9 100644
 --- a/lib/sqlalchemy/orm/strategies.py
 +++ b/lib/sqlalchemy/orm/strategies.py
 @@ -535,8 +535,9 @@ class LazyLoader(AbstractRelationshipLoader):

          pending = not state.key

 -        # don't autoflush on pending
 -        if pending:
 +        # don't autoflush on pending, or if
 +        # NO_AUTOFLUSH is in passive flags
 +        if pending or passive & attributes.NO_AUTOFLUSH:
              q = q.autoflush(False)

          if state.load_path:
 }}}

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2921#comment:1>
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