Historical versions of attachments are considered as dependants to be re-indexed when their page is updated

Issue Summary

Historical versions of attachments are considered as dependants to be re-indexed if their page is updated. This will lead to an issue when new contents cannot be indexed timely and the content index is backing up. The system is also hammered by the huge amount of unnecessary readings from the cache (to check if the versions are indexable) and I/O operations (for deleting the Lucene documents of historical versions of attachments).

Steps to Reproduce

1. Move a page that contains thousands of versions of attachments.
2. Monitor the journal main_index. It will be updated slowly to keep up with the last journal entry ID in the database.

Expected Results

Only the latest version of attachments on the updated page will be re-indexed.

Actual Results

All Lucene documents of historical versions of attachments are deleted. No new documents for them are added.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available