I'm wondering if it is safe to add a lookup that will have >50,000 children under a single parent. The child table has lots of inserts and lots of updates happening in parallel. However, the lookup itself is pretty static. It will not be populated on insert, and only a single transaction at a time will be updating the lookup.
Will lookup skew be a problem on this table?
From what I understand lookup skew is bad because it causes update/insert failures due to row locking issues. The parent record must be locked during update/insert of a child record. If the parent record is not locked then it could be deleted during the update/insert and create a referential integrity issue.
Does the parent record get locked even if the lookup field is not updated?
If the parent record only gets locked when the lookup field is updated, I think that the situation would be safe from lookup skew issues.