Summary

The linked subtask panel shows an error instead of loading the subtask.

This can occur after a migration from Jira Cloud to Jira Datacenter, or for other reasons. 

 There is a sequence value which determines the order in which the subtasks for an issue should display.  A sequence of nulls causes an error.  Any numeric values will resolve the problem, including all zeros.

• the sequence value is for showing what order to display the subtasks
  • A 0 will show the link first, with a "1."
  • A 1 will show the link second, with "2."
  • A null causes a failure.
  • Setting two subtasks with the same source value to have the same sequence value, like 0, will cause an arbitrary load order.

• Unlike most database edits, this info is read live;
  • No restart is required for these changes to take effect.

Environment

Jira Datacenter 8.20.6
(Known to occur after migration from Jira Cloud)

Diagnosis

 Subtasks don't show, and there is an error/stack trace instead: 

 Subtasks should show up in a numbered list:

Error message in the subtask panel (excerpt)

An error occurred whilst rendering this message. Please contact the administrators, and inform them of this bug. 
Details: ------- org.apache.velocity.exception.MethodInvocationException: Invocation of method 'getHtml' in class com.atlassian.jira.web.component.subtask.SubTaskSequenceColumnLayoutItem
 threw exception java.lang.NullPointerException: null value in entry: actualSequence=null at templates/jira/issue/table/macros.vm[line 117, column 34] at
 org.apache.velocity.runtime.parser.node.ASTMethod.handleInvocationException(ASTMethod.java:337) at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:284) at 
...
com.atlassian.velocity.htmlsafe.introspection.UnboxingMethod.invoke(UnboxingMethod.java:28) at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:270) ... 473 more

 Below queries are written for Postgres and may need revision for other database systems.

Specific Link Type and Issue

1. Confirm the ID for the sub-task link:

   SELECT * FROM issuelinktype WHERE linkname = 'jira_subtask_link';

    It is expected the ID will be 10100.  This will be assumed in the following steps.

2. Confirm the ID for an affected Issue:

   1. Get the Issue ID

      1. Either Get the Issue ID from the interface

      2. Or get the Issue ID using the Project Key & Issue Key (replace KEY & 1234 below):

         SELECT jiraissue.id
         FROM jiraissue
         JOIN project ON jiraissue.project = project.id
         WHERE project.pkey = 'KEY' AND jiraissue.issuenum = 1234;

   2. Confirm that the sequence is null for that Issue (replace sourceID below):

      select * from issuelink where linktype = 10100 and SOURCE = sourceID;

       If the sequence values returned are null, then the solution below will help.

General Subtask/Parent check

1. See if any Subtask/Parent links are null, which none should be.  If you have a problem with another linktype, please use the specific instructions above.

   SELECT count(*) FROM issuelink WHERE linktype = 10100 AND sequence IS NULL; 

Cause

• There are null values in the sequence column of the issuelink table.
• This has been observed in Instances migrated from Jira Cloud to Jira DC.
  • null values inserted by other means can also cause this problem.

Solution

1.  Please make a native database backup before modifying the database.
   

2. Run the following query, to fill the nulls with 0s:
   

   UPDATE issuelink SET sequence = 0 WHERE linktype = 10100 AND sequence IS NULL;

3. Test the Issue page; the solution should take effect immediately.