Count each source's upstream and its records in the corpus, one source after the
other. The upstream count of an aggregator-backed Land is the aggregator's, and its
basis says so. Throws only for a period outside PERIOD_RANGE; a source that
fails to count is a row with a note.
Count each source's upstream and its records in the corpus, one source after the other. The upstream count of an aggregator-backed Land is the aggregator's, and its
basissays so. Throws only for aperiodoutsidePERIOD_RANGE; a source that fails to count is a row with anote.