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Strange behaviour of LCEvent::takeCollection() [message #1660] Sun, 07 December 2008 12:18 Go to previous message
killenberg
Messages: 125
Registered: July 2005
Location: CERN
Hello,

the behaviour of LCEvent::takeCollection() is not as I expected.
The ownership is transferred correctly, but
  • the collection stays in the event I took it from.
  • the collection is set to transient.

If I take the collection away from the event I would expect that the collection is removed from the event. And I can't call removeCollection() since this deletes the collection from memory. This definitely is a bug since an event which gave away the ownership must not delete the collection.

That fact that it is set transient is also not very helpful, since I want to add it to another event (compose an event from several subevents) and write it to disc. So I remove the transient flag which means it will also be non-transient in the subevent I took it from. Currently this is not a problem since I delete the subevent, which correctly does not delete the collections that don't belong to it.

Here are my proposals for improvement:
  • If it is desired that the taken collection stays in the source object, the removeCollection() should be modified so the collection which does no longer belong to the event is not deleted.
  • In any case the transientness of the collection should not be modified. One could modify the streamer so only collections belonging to the event are written to disc.

Greetings

Martin


Martin Killenberg

CERN
martin.killenberg@cern.ch
 
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