Revision karma allocator glacial and needed to be disabled

The following query no longer performs adequately under PostgreSQL 8.4:

SELECT Revision.*
FROM Revision, RevisionAuthor, ValidPersonCache
WHERE
    Revision.revision_author = RevisionAuthor.id
    AND RevisionAuthor.person = ValidPersonCache.id
    AND NOT Revision.karma_allocated
    AND EXISTS (
        SELECT true FROM Branch, BranchRevision
        WHERE BranchRevision.revision = Revision.id
            AND BranchRevision.branch = Branch.id
            AND (
                NOT (Branch.product IS NULL)
                OR NOT (Branch.distroseries IS NULL)))
LIMIT 100 OFFSET 0;

The simplest fix is to add a LIMIT into the EXISTS subquery, which I think restores the 8.3 behavior we were relying on:

SELECT Revision.*
FROM Revision, RevisionAuthor, ValidPersonCache
WHERE
    Revision.revision_author = RevisionAuthor.id
    AND RevisionAuthor.person = ValidPersonCache.id
    AND NOT Revision.karma_allocated
    AND EXISTS (
        SELECT true FROM Branch, BranchRevision
        WHERE BranchRevision.revision = Revision.id
            AND BranchRevision.branch = Branch.id
            AND (
                NOT (Branch.product IS NULL)
                OR NOT (Branch.distroseries IS NULL))
        LIMIT 1)
LIMIT 100 OFFSET 0;

A better fix is to return up to 100 rows instead of exactly 100 rows, which can be performed 10x faster:

SELECT DISTINCT * FROM (
SELECT Revision.*
FROM Revision, RevisionAuthor, ValidPersonCache, Branch, BranchRevision
WHERE
    Revision.revision_author = RevisionAuthor.id
    AND RevisionAuthor.person = ValidPersonCache.id
    AND NOT Revision.karma_allocated
    AND BranchRevision.revision = Revision.id
    AND BranchRevision.branch = Branch.id
    AND (NOT (Branch.product IS NULL) OR NOT (Branch.distroseries IS NULL))
LIMIT 100) AS Whatever;