Parsed test spec with 2 sessions

starting permutation: wxry1 c1 r2 wyrx2 c2
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
step c1:  COMMIT; 
step r2:  SELECT TRUE; 
bool           

t              
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
ERROR:  child row exists
step c2:  COMMIT; 

starting permutation: wxry1 r2 c1 wyrx2 c2
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
step r2:  SELECT TRUE; 
bool           

t              
step c1:  COMMIT; 
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
ERROR:  could not serialize access due to read/write dependencies among transactions
step c2:  COMMIT; 

starting permutation: wxry1 r2 wyrx2 c1 c2
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
step r2:  SELECT TRUE; 
bool           

t              
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
step c1:  COMMIT; 
step c2:  COMMIT; 
ERROR:  could not serialize access due to read/write dependencies among transactions

starting permutation: wxry1 r2 wyrx2 c2 c1
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
step r2:  SELECT TRUE; 
bool           

t              
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
step c2:  COMMIT; 
step c1:  COMMIT; 
ERROR:  could not serialize access due to read/write dependencies among transactions

starting permutation: r2 wxry1 c1 wyrx2 c2
step r2:  SELECT TRUE; 
bool           

t              
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
step c1:  COMMIT; 
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
ERROR:  could not serialize access due to read/write dependencies among transactions
step c2:  COMMIT; 

starting permutation: r2 wxry1 wyrx2 c1 c2
step r2:  SELECT TRUE; 
bool           

t              
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
step c1:  COMMIT; 
step c2:  COMMIT; 
ERROR:  could not serialize access due to read/write dependencies among transactions

starting permutation: r2 wxry1 wyrx2 c2 c1
step r2:  SELECT TRUE; 
bool           

t              
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
step c2:  COMMIT; 
step c1:  COMMIT; 
ERROR:  could not serialize access due to read/write dependencies among transactions

starting permutation: r2 wyrx2 wxry1 c1 c2
step r2:  SELECT TRUE; 
bool           

t              
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
step c1:  COMMIT; 
step c2:  COMMIT; 
ERROR:  could not serialize access due to read/write dependencies among transactions

starting permutation: r2 wyrx2 wxry1 c2 c1
step r2:  SELECT TRUE; 
bool           

t              
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
step c2:  COMMIT; 
step c1:  COMMIT; 
ERROR:  could not serialize access due to read/write dependencies among transactions

starting permutation: r2 wyrx2 c2 wxry1 c1
step r2:  SELECT TRUE; 
bool           

t              
step wyrx2:  DELETE FROM parent WHERE parent_id = 0; 
step c2:  COMMIT; 
step wxry1:  INSERT INTO child (parent_id) VALUES (0); 
ERROR:  parent row missing
step c1:  COMMIT; 
