IF an IN Clause in JQL contains a single element which does not exist (e.g. a non-existent issue key), then the entire Query fails.

e.g. a Valid IN CLAUSE

• https://jira.atlassian.com/rest/api/2/search?jql=issuekey%20in%20(JRA-9)

and invalid IN CLAUSE

• https://jira.atlassian.com/rest/api/2/search?jql=issuekey%20in%20(JRA-9,%20JRA-0)
  yields:
• {"errorMessages":["An issue with key 'JRA-0' does not exist for field 'issuekey'."],"errors":{}}

We would like the IN clause in JQL to operate the same as the IN Clause in SQL.
If one or more elements do not exist, then they should simply be ignored.

The reason for this is to avoid N queries to a JIRA instance when looking for bulk JIRA Issue information, such as is needed in the FishEye Release Report. i.e. - here is a bunch of JIRA issues - go and fetch their summaries.
If the above error messages were machine readable, I guess we could get away with 2 queries - the first one to filter the issue keys that don't exist and the second one to query the issue summaries.