Deleting seeds leaves orphaned historical seeds

[justinlittman]

These orphaned historical seeds cause deserialization errors when importing the collection.

Note that this is for actual deleting of seeds, not just marking a seed as inactive.

Steps to reproduce:

1. Create a Twitter user timeline collection with multiple seeds.
2. Perform some harvests.
3. Delete a seed using the Admin interface.
4. Serialize the collection using the serializecollection management command.
5. Copy the collection files to a clean SFM instance.
6. Deserialize the collection using the deserializecollection management command.

Excepted result:
Collection is imported.

Actual result:
Deserialization error

The primary reason that seeds are manually deleted is because of duplicate seeds. The need for this should be reduced with improvements in seed duplication validation.

Workaround:
Delete the orphaned historical seeds with:

delete from ui_harvest_historical_seeds
where historicalseed_id in
(
select hs.history_id
from ui_historicalseed hs
left outer join ui_seed s on hs.id=s.id
where s.id is null);

delete from ui_historicalseed hs
where hs.id not in
(select s.id from ui_seed s);