I am researching into migration of chatter data between two instances of Salesforce. Specifically I need to migrate chatter data within Collaboration Groups in a Community. I found all the posts from within the groups within the FeedItem table, including the related "answers", which really are just records in FeedComment table. What I cannot find is the relationship which makes the FeedItem records appear under a specific CollaborationGroup.
I looked through every relationship on FeedItem, and cannot find how it is linked to specific CollaborationGroup. I took one FeedItem as an example, it appears under one of the CollaborationGroup records, but its ParentId refers to a User record, RelatedRecordId refers to a ContentDocument record, InsertedById refers to user record, CreatedById refers to User record. I don't see any junction objects either, which link that post (FeedItem) to the CollaborationGroup record.
Does anyone know how to identify the child FeedItem records of type QuestionPost in a given CollaborationGroup record?