/rosetta/imports/ page timing out

Kiko's analysis of OOPS-117B155

"They are actually lots of TeamParticipation queries that are interspersed with:

        57. 637 0ms SELECT mimetype, last_accessed, expires,
                                filename, content FROM LibraryFileAlias
                                WHERE id = 1850504
        58. 637 1ms SELECT filename, deleted FROM LibraryFileAlias,
                                LibraryFileContent WHERE LibraryFileContent.id =
                                LibraryFileAlias.content AND LibraryFileAlias.id
                                = 1850504

    It appears that we could avoid at least the first query by using
    prejoining on TranslationImportQueueEntry, for the 'content' field.
    If we had double-dotted prejoining we could do "content.content" and
    avoid the second query as well."

OOPS-290C291