Hi all, not sure if this is for novice or general - however...
Fiddle here:
> https://dbfiddle.uk/?rdbms=postgres_12&fiddle=49de306c75e85ce4ba900719e2545c32
> SHOW TRANSACTION ISOLATION LEVEL;
Result:
> transaction_isolation
> read committed
So far, so good, then
> CREATE TABLE x (y INT, z VARCHAR (25));
> INSERT INTO x VALUES (1, 'One'), (2, 'Two'), (3, 'Three');
and now for a transaction:
> START TRANSACTION;
> SELECT CURRENT_TIMESTAMP(6);
> SELECT * FROM x;
> SELECT CURRENT_TIMESTAMP(6);
> COMMIT;
Result:
> current_timestamp 2021-05-13 15:51:11.194766+01
> y z
> 1 One
> 2 Two
> 3 Three
> current_timestamp 2021-05-13 15:51:11.194766+01
Now, my understanding of ISOLATION LEVEL = read-committed is that the
current_timestamp should change going through the transaction and that
it should not change when the level is serializable.
Am I wrong about this?
I did a similar experiment with MariaDB and none of the times are the same:
> https://dbfiddle.uk/?rdbms=mariadb_10.5&fiddle=ad2d3b2f360c3dbe59fa00f623a3db6b
Have I misunderstood transactions and isolation levels...
URLs, references and pointers to same appreciated.
TIA and rgs,
Pól...
