Parsed test spec with 2 sessions

starting permutation: merge1 c1 select2 c2
step merge1: MERGE INTO target t USING (SELECT 1 as key, 'merge1' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge1';
step c1: COMMIT;
step select2: SELECT * FROM target;
key|val   
---+------
  1|merge1
(1 row)

step c2: COMMIT;

starting permutation: merge1 c1 merge2 select2 c2
step merge1: MERGE INTO target t USING (SELECT 1 as key, 'merge1' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge1';
step c1: COMMIT;
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2';
step select2: SELECT * FROM target;
key|val                     
---+------------------------
  1|merge1 updated by merge2
(1 row)

step c2: COMMIT;

starting permutation: insert1 merge2 c1 select2 c2
step insert1: INSERT INTO target VALUES (1, 'insert1');
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; <waiting ...>
step c1: COMMIT;
step merge2: <... completed>
ERROR:  duplicate key value violates unique constraint "target_pkey"
step select2: SELECT * FROM target;
ERROR:  current transaction is aborted, commands ignored until end of transaction block
step c2: COMMIT;

starting permutation: merge1 merge2 c1 select2 c2
step merge1: MERGE INTO target t USING (SELECT 1 as key, 'merge1' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge1';
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; <waiting ...>
step c1: COMMIT;
step merge2: <... completed>
ERROR:  duplicate key value violates unique constraint "target_pkey"
step select2: SELECT * FROM target;
ERROR:  current transaction is aborted, commands ignored until end of transaction block
step c2: COMMIT;

starting permutation: merge1 merge2 a1 select2 c2
step merge1: MERGE INTO target t USING (SELECT 1 as key, 'merge1' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge1';
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; <waiting ...>
step a1: ABORT;
step merge2: <... completed>
step select2: SELECT * FROM target;
key|val   
---+------
  1|merge2
(1 row)

step c2: COMMIT;

starting permutation: delete1 insert1 c1 merge2 select2 c2
step delete1: DELETE FROM target WHERE key = 1;
step insert1: INSERT INTO target VALUES (1, 'insert1');
step c1: COMMIT;
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2';
step select2: SELECT * FROM target;
key|val                      
---+-------------------------
  1|insert1 updated by merge2
(1 row)

step c2: COMMIT;

starting permutation: delete1 insert1 merge2 c1 select2 c2
step delete1: DELETE FROM target WHERE key = 1;
step insert1: INSERT INTO target VALUES (1, 'insert1');
step merge2: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN NOT MATCHED THEN INSERT VALUES (s.key, s.val) WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2'; <waiting ...>
step c1: COMMIT;
step merge2: <... completed>
ERROR:  duplicate key value violates unique constraint "target_pkey"
step select2: SELECT * FROM target;
ERROR:  current transaction is aborted, commands ignored until end of transaction block
step c2: COMMIT;

starting permutation: delete1 insert1 merge2i c1 select2 c2
step delete1: DELETE FROM target WHERE key = 1;
step insert1: INSERT INTO target VALUES (1, 'insert1');
step merge2i: MERGE INTO target t USING (SELECT 1 as key, 'merge2' as val) s ON s.key = t.key WHEN MATCHED THEN UPDATE set val = t.val || ' updated by merge2';
step c1: COMMIT;
step select2: SELECT * FROM target;
key|val    
---+-------
  1|insert1
(1 row)

step c2: COMMIT;