Linker custom fields not visible after upgrade to JIRA 6
Symptoms
In the old version of JIRA, there was JIRA Linker plugin that was used to add custom fields to store links. If an instance with these custom fields is upgraded to JIRA 6.x then these custom fields are no longer visible after the upgrade.
Cause
This plugin has been removed from JIRA 5.0 and the functionality has been added to core JIRA. However, there is no custom field type key : 'com.atlassian.jira.plugin.linker:linker' on the new JIRA versions. Hence JIRA is not able to show these fields on the UI.
Resolution
Here are the steps you can take in order to convert the Linker custom fields to Url custom fields.
Stop JIRA
Run the following query in the database :
update customfield set customfieldtypekey='com.atlassian.jira.plugin.system.customfieldtypes:url', customfieldsearcherkey='com.atlassian.jira.plugin.system.customfieldtypes:exacttextsearcher' where customfieldtypekey='com.atlassian.jira.plugin.linker:linker';
Start JIRA
Notice that the Linker custom fields are now working again.