Creating the indexes below improves performance of the Remove Issue dramatically:
create index ix1_notificationinstance on notificationinstance (source,notificationtype,emailaddress) tablespace jira_index;
create index ix1_OS_HISTORYSTEP on OS_HISTORYSTEP (ENTRY_ID) tablespace jira_index;
create index ix1_jiraissue on jiraissue (workflow_id) tablespace jira_index;
create index ix1_OS_CURRENTSTEP on OS_CURRENTSTEP (ENTRY_ID) tablespace jira_index;
The above commands are for the Oracle database. If you maintain statistics updated, the commands below update the statistics for these new indexes. Replace 'JIRA' for the schema your jira database has been created in:
execute dbms_stats.gather_index_stats(indname => 'IX1_NOTIFICATIONINSTANCE', ownname => 'JIRA')
execute dbms_stats.gather_index_stats(indname => 'IX1_OS_CURRENTSTEP', ownname => 'JIRA')
execute dbms_stats.gather_index_stats(indname => 'IX1_OS_HISTORYSTEP', ownname => 'JIRA')
execute dbms_stats.gather_index_stats(indname => 'IX1_JIRAISSUE', ownname => 'JIRA')