On 7/23/19 8:43 AM, Cyril Champier wrote:
Hi,
In this documentation
<https://www.postgresql.org/docs/9.1/queries-order.html>, it is said:
If sorting is not chosen, the rows will be returned in an
unspecified order. The actual order in that case will depend on the
scan and join plan types and the order on disk, but it must not be
relied on.
I would like to know if there is any way to change that to have a "real"
random behaviour.
My use case:
At Doctolib, we do a lot of automatic tests.
Sometimes, people forgot to order their queries. Most of the time, there
is no real problem on production. Let say, we display a user list
without order.
When a developer writes a test for this feature, he will create 2 users
A and B, then assert that they are displayed "[A, B]".
99% of the time the test will be ok, but sometimes, the displayed list
will be "[B,A]", and the test will fail.
One solution could be to ensure random order with an even distribution,
so that such failing test would be detected quicker.
Is that possible? Maybe with a plugin?
Not that I know of.
A possible solution given below:
test_(postgres)> insert into t1 values (1, 'dog'), (2, 'cat'), (3, 'fish');
INSERT 0 3
test_(postgres)> select * from t1 ;
a | b
---+------
1 | dog
2 | cat
3 | fish
(3 rows)
test_(postgres)> update t1 set b = 'dogfish' where a =1;
UPDATE 1
test_(postgres)> select * from t1 ;
a | b
---+---------
2 | cat
3 | fish
1 | dogfish
(3 rows)
An UPDATE reorders the rows. Maybe throw an UPDATE into the test after
creating the users to force an 'out of order' result?
Thanks,
Cyril
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
