Symptoms

After importing data from another instance using a Confluence XML Backup you will notice that some questions/answers will be missing or will not show up in in the unanswered/Recent section:

The popular tab may also display no questions.

The following appears in the atlassian-confluence.log:

2014-08-11 13:27:03,328 ERROR [ajp-bio-8010-exec-2] [atlassian.confluence.servlet.ConfluenceServletDispatcher] sendError Could not execute action
 -- url: /questions | userName: lavitz | referer: http://confluence:8090/admin/mail/viewmailqueue.action
java.lang.IllegalArgumentException: author is required
	at com.atlassian.confluence.plugins.questions.model.QuestionImpl.<init>(QuestionImpl.java:49)
	at com.atlassian.confluence.plugins.questions.model.QuestionImplBuilder.build(QuestionImplBuilder.java:118)
	at com.atlassian.confluence.plugins.questions.contenttype.repository.ContentTypeMapper.toQuestion(ContentTypeMapper.java:93)
	at com.atlassian.confluence.plugins.questions.contenttype.repository.ContentTypeMapper.toAnswer(ContentTypeMapper.java:120)
	at com.atlassian.confluence.plugins.questions.contenttype.repository.ContentTypeMapper$1.apply(ContentTypeMapper.java:175)
	at com.atlassian.confluence.plugins.questions.contenttype.repository.ContentTypeMapper$1.apply(ContentTypeMapper.java:171)
	at com.google.common.collect.Iterators$8.next(Iterators.java:812)
	at com.google.common.collect.Lists.newArrayList(Lists.java:139)

Diagnosis

To validate if you have orphan questions or answers please run the queries below:

SELECT * FROM CONTENT WHERE PLUGINKEY IN ('com.atlassian.confluence.plugins.confluence-questions:answer', 'com.atlassian.confluence.plugins.confluence-questions:comment') AND PARENTCCID IS NULL AND PREVVER IS NULL;

SELECT * FROM CONTENT WHERE PLUGINKEY LIKE 'com.atlassian.confluence.plugins.confluence-questions:%' AND CREATOR IS NULL;

If any of the above returned results please read the Cause and Resolution sections.

Cause

During the xml import process the data was corrupted and some of the questions/answers were orphaned (they do not have a parent question or creator), due to that, the plugin will not be able to run its indexing tasks on the startup. This will cause the unanswered/Recent section to not show any results and some questions or sections will no longer be reachable.

Resolution

The resolution for this misbehaviour is to map the orphan answers to a parent question and the orphan questions to a creator. Based on the results on the diagnostic section you might only need to follow one of below set of instructions instead of both.

In case of answers without questions:

In case of questions and answers without a creator:

1. Choose a existing user or create a new one to be the author of the orphan answers/questions.
2. Shutdown Confluence.

3. Take note of the user key for that chosen user in step 1:

   SELECT user_key
   FROM user_mapping
   WHERE username = 'admin'

   Make sure to replace the admin value in the above query with the user name of the chosen user from step 1.

4. Now run the below update query so we can link the orphan answers/question to the chosen user:

   UPDATE CONTENT
   SET CONTENT.creator = "8a8ba1dc46f894650146f97ba5930003", content.lastmodifier = "8a8ba1dc46f894650146f97ba5930003"
   WHERE CONTENT.pluginkey LIKE 'com.atlassian.confluence.plugins.confluence-questions:%'
   AND CONTENT.CREATOR IS NULL;

   Make sure to replace the "8a8ba1dc46f894650146f97ba5930003" value in above query with the user key from step 3.

5. Start Confluence.

6. Check if the feature is working again.