# Write skew test. # # This test has two serializable transactions: one which updates all # 'apple' rows to 'pear' and one which updates all 'pear' rows to # 'apple'. If these were serialized (run one at a time) either # value could be present, but not both. One must be rolled back to # prevent the write skew anomaly. # # Any overlap between the transactions must cause a serialization failure. setup { CREATE TABLE test (i int PRIMARY KEY, t text); INSERT INTO test VALUES (5, 'apple'), (7, 'pear'), (11, 'banana'); } teardown { DROP TABLE test; } session "s1" setup { BEGIN ISOLATION LEVEL SERIALIZABLE; } step "rwx1" { UPDATE test SET t = 'apple' WHERE t = 'pear'; } step "c1" { COMMIT; } session "s2" setup { BEGIN ISOLATION LEVEL SERIALIZABLE; } step "rwx2" { UPDATE test SET t = 'pear' WHERE t = 'apple'} step "c2" { COMMIT; }