What's the purpose of transaction_id?

[sobrinho]

I can see all my records having the same value of id on that column, what's the purpose?

[westonganger]

As stated directly in the readme

It will store in the version_associations table additional information to correlate versions of the association and versions of the model when the associated record is changed. When reifying the model, it will utilize this table, together with the transaction_id to find the correct version of the association and reify it. The transaction_id is a unique id for version records created in the same transaction. It is used to associate the version of the model and the version of the association that are created in the same transaction.

[sobrinho]

But why it does exist if AFAIK all the values on it is exactly the same value of the primary key of the version_associations table?