Restoring a page to a previous version creates historic entries in CONTENT_LABEL

This bug can cause undesired results in Confluence, such as the page properties report macro showing multiple versions of the same page in a single report.

Steps to Reproduce

1. Create a page with the label "test"
2. Edit the page created in step 1, and save (this creates version 2 of that page)
3. Restore the page to version 1 (which now creates version 3 which is reverted from v1)

Notice that after the steps above, you will now obtain both version 2 and version 3 of the page, linked to the "test" label in the CONTENT_LABEL table:

SELECT * FROM CONTENT c JOIN CONTENT_LABEL cl ON c.CONTENTID = cl.CONTENTID JOIN LABEL l on cl.LABELID = l.LABELID WHERE l.NAME = 'test';

If the steps above are reproduced this way:

1. Create a page with the page properties macro inserted (with label="test")
2. Edit the page created in step 1, and save (this creates version 2 of that page)
3. Restore the page to version 1 (which now creates version 3 which is reverted from v1)
4. Create a page with the page properties report macro inserted, set to find pages with label="test"

You will realize that the page properties report macro in the page created in Step 4 will list down both version 2 and version 3 of the same page in that macro.

Workaround

1. Take a backup of the database
2. Run this query to remove these entries from CONTENT_LABEL:

   DELETE FROM CONTENT_LABEL WHERE CONTENTID IN  (SELECT CONTENTID FROM CONTENT WHERE PREVVER IS NOT NULL);
   

3. Flush all the caches via Confluence Admin >> Cache Statistics