void DocumentSourceSort::populate() {
        /* make sure we've got a sort key */
        verify(vSortKey.size());

        if (!limitSrc)
            populateAll();
        else if (limitSrc->getLimit() == 1)
            populateOne();
        else
            populateTopK();

        populated = true;
    }
    void DocumentSourceSort::populate() {
        /* make sure we've got a sort key */
        verify(vSortKey.size());

        if (!limitSrc)
            populateAll();
        else if (limitSrc->getLimit() == 1)
            populateOne();
        else
            populateTopK();

        /* start the sort iterator */
        docIterator = documents.begin();

        if (docIterator != documents.end())
            pCurrent = docIterator->doc;
        populated = true;
    }