Parsed test spec with 4 sessions

starting permutation: rx1 wx2 c2 wx3 ry3 wy4 rz4 c4 c3 wz1 c1
step rx1:  SELECT * FROM t WHERE id = 1000000; 
id             txt            

1000000                       
step wx2:  UPDATE t SET txt = 'b' WHERE id = 1000000; 
step c2:  COMMIT; 
step wx3:  UPDATE t SET txt = 'c' WHERE id = 1000000; 
step ry3:  SELECT * FROM t WHERE id = 500000; 
id             txt            

500000                        
step wy4:  UPDATE t SET txt = 'd' WHERE id = 500000; 
step rz4:  SELECT * FROM t WHERE id = 1; 
id             txt            

1                             
step c4:  COMMIT; 
step c3:  COMMIT; 
ERROR:  could not serialize access due to read/write dependencies among transactions
step wz1:  UPDATE t SET txt = 'a' WHERE id = 1; 
step c1:  COMMIT; 
