def METHOD_NAME(xrefs):
    """
    Given a list of xrefs to search for, return a dict of lists
    of result values. Xrefs that have no corresponding issues are
    not represented in the dictionary.
    """
    # The IN operator does multiple sequential queries and ORs them
    # together. This is slow here-- a range query is faster, since
    # this is used to get xrefs for a set of contiguous builds.
    if not xrefs:  # nothing => nothing
        raise ndb.Return({})
    xrefs = set(xrefs)
    issues = yield GHIssueDigest.query(
        GHIssueDigest.xref >= min(xrefs),
        GHIssueDigest.xref <= max(xrefs)).fetch_async(batch_size=500)
    refs = {}
    for issue in issues:
        for xref in issue.xref:
            if xref in xrefs:
                refs.setdefault(xref, []).append(issue)
    raise ndb.Return(refs)