column 0 keys: a b c d e f g key a expects: a1 a2 a3, computes: a1 a3 column 1 keys: 1 2 3 key 1 expects: a1, computes: a1 compare cells of a1 and a1 key 2 expects: a2, computes: missing: a2, surplus: key 3 expects: a3, computes: a3 compare cells of a3 and a3 key b expects: b1 b2, computes: b1 b2 column 1 keys: 1 2 key 1 expects: b1, computes: b1 compare cells of b1 and b1 key 2 expects: b2, computes: b2 compare cells of b2 and b2 key c expects: c1, computes: c1 c2 column 1 keys: 1 2 key 1 expects: c1, computes: c1 compare cells of c1 and c1 key 2 expects: , computes: c2 missing: , surplus: c2 key d expects: d1, computes: missing: d1, surplus: key e expects: , computes: e1 missing: , surplus: e1 key f expects: f1 f1 f1, computes: f1 f1 column 1 keys: 1 key 1 expects: f1 f1 f1, computes: f1 f1 can't distinguish f1 f1 f1 and f1 f1 key g expects: g1 g2, computes: g2 g1 column 1 keys: 1 2 key 1 expects: g1, computes: g1 compare cells of g1 and g1 key 2 expects: g2, computes: g2 compare cells of g2 and g2