Ha. Is this sane?
DB.query_single('SELECT name, length(value) FROM "post_custom_fields" WHERE post_id=20')
=> ["calendar-details", 83361791, "post_detected_lang", 2]
So, the value column of this specific calendar-details item contains ~80MB worth of data. I believe we are on to something here.
Apparently, this is the only item carrying such a large payload within its calendar-details value.
print(DB.query("SELECT post_id, length(value) FROM post_custom_fields WHERE name='calendar-details' ORDER BY post_id").map { |r| r.post_id.to_s + ": " + r.length.to_s }.join("\n"))
20: 83361791
84: 113
133: 113
177: 58
223: 2
263: 113
379: 112
385: 130
439: 112
456: 112
457: 58
495: 117
552: 2