14 .PostgreSQL
Session A Session B
> begin; > begin;
> set transaction isolation level repeatable > set transaction isolation level repeatable read;
read;
> update test set value = value + 1 where id = 1;
UPDATE 1
> update test set value = value + 1 where id = 1;
block...
> commit; ERROR: could not serialize access due to
COMMIT concurrent update
15 .MySQL
Session A Session B
> begin; > begin;
> update test set value = value + 1 where id = 1;
Query OK, 1 row affected
> update test set value = value + 1 where id = 1;
block...
> commit; Query OK, 1 row affected
Query OK, 0 rows affected
> commit;
Query OK, 0 rows affected
16 .MySQL
Session A Session B
> create table t (i int);
> begin;
> select * from t;
Empty set
> insert into t values (1);
Query OK, 1 row affected
> select * from t for update;
1 row in set
> select * from t;
Empty set
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