Confluence might show blank content or an old version of a page when an user tries to edit a page with Collaborative Editing enabled

Issue Summary

When Collaborative Editing is enabled in Confluence and users try to edit a page, they might hit a bug on which a blank page is shown in the editor.
Sometimes, it is not a blank page, but an old version of it.

Environment

This bug was reproduced on 6.6, 6.13 and 6.15.4.
Although not tested, this should affected any version from 6.0 onward.

Steps to Reproduce

Below are described two ways to hit this bug, but with different characteristics to user, although the bug trigger is the same.
Because of simplicity, the first option might be more common than the other, which is when the user sees a blank page when accessing the editor.

Option 1

1. Install a vanilla instance of Confluence.
2. Publish a new page with no content.
   • If you check records related to this page in the CONTENT table you have 2 rows.
   • The row related to the draft has creationdate and lastmoddate equal to null.
     
3. Disable Collaborative Editing.
4. Edit the same page, add new content to it and save it.
   • If you check records related to this page in the CONTENT table, you have 3 rows.
5. Enable Collaborative Editing.
   • The draft record that was created a few steps ago won't be removed as a stale draft because its timestamps are null.
6. Access the same page as before and click on Edit.

Expected Results

Confluence shows in the editor the contents of the last published page.

Actual Results

Confluence shows in the editor a blank page.

Option 2

1. Install a vanilla instance of Confluence.
2. Disable Collaborative Editing.
3. Create a page with a sample content.
   
   • If you check records related to this page in the CONTENT table, you have just one row.
     
4. Enable Collaborative Editing.
5. Access the page created a few steps before and click on Edit.
6. Without changing anything on the contents, click on Close to exit the editor.
   • If you check records related to this page in the CONTENT table, now you have 2 rows.
   • The new row added to the table is related to the draft record and has creationdate and lastmoddate equal to null.
     
7. Disable Collaborative Editing.
8. Edit the same page again, add new content to it and save it.
   
   • If you check records related to this page in the CONTENT table, you have 3 rows.
     
9. Enable Collaborative Editing.
   • The draft record that was created a few steps ago won't be removed as a stale draft because its timestamps are null.
10. Access the same page as before and click on Edit.

Expected Results

Confluence shows in the editor the contents of the last published page.

Actual Results

Confluence shows in the editor an old version of the page, which is related to the draft record created when Collaborative Editing was first enabled.

Notes

This bug is related to CONFSERVER-57458 in a way that it shows the same characteristics to the end user.
A bug new record was created because the trigger of is completely different.

Workaround

1. First, let's execute the following SQL query to identify how many affected pages are there with NULL creationdate and lastmoddate.

   SELECT count(1)
   FROM CONTENT d
   JOIN CONTENT c
     ON d.prevver = c.contentid
   WHERE d.content_status = 'draft'
     AND d.prevver IS NOT NULL
     AND (c.lastmoddate is not null and d.lastmoddate is null);
   

1. Then, please navigate to the <Confluence-Base-URL>/admin/do-force-upgrade.action page.
2. Next, set the drop-down to nullModificationDateDraftUpgradeTask and click on the Force Upgrade button.
3. Lastly, please run the query that we ran on Step no. 1 again to check how many affected pages are left in the Confluence DB - we're expecting 0 result to be returned here.