EXPLAIN
SELECT src1.key as k1, src1.value as v1, 
       src2.key as k2, src2.value as v2 FROM 
  (SELECT * FROM src WHERE src.key < 10) src1 
    JOIN 
  (SELECT * FROM src WHERE src.key < 10) src2
  SORT BY k1, v1, k2, v2;

EXPLAIN FORMATTED
SELECT src1.key as k1, src1.value as v1, 
       src2.key as k2, src2.value as v2 FROM 
  (SELECT * FROM src WHERE src.key < 10) src1 
    JOIN 
  (SELECT * FROM src WHERE src.key < 10) src2
  SORT BY k1, v1, k2, v2;

SELECT src1.key as k1, src1.value as v1, 
       src2.key as k2, src2.value as v2 FROM 
  (SELECT * FROM src WHERE src.key < 10) src1 
    JOIN 
  (SELECT * FROM src WHERE src.key < 10) src2
  SORT BY k1, v1, k2, v2;