Re: Default ordering option

On 7/25/19 12:43 AM, Cyril Champier wrote:
> *Adrian*:
>
> If order is not an issue in the production code why test for it in the
> test code?
>
>
> In many cases, it would not be a problem in tests if we had an unordered
> array comparison helper.
> But in other cases, it is a production issue.
> In ruby ActiveRecord for exemple, you can do `Patient.find_by(last_name:
> 'champier')`,
> which translates to `SELECT  "patients".* FROM "patients" WHERE
> "patients"."last_name" = 'champier' LIMIT 1`.
> If last_name is not unique, the returned record will be random.

Are you really looking for a pseudo-random name?

If so would not(warning not a Ruby developer, so below is tentative):

Patient.where(["last_name = :last_name", {last_name:
"champier"}]).order('RANDOM()').first

work better?

If not why not use something that returns all possible matches?

>
> So yes, everything as to be randomized, because the sources are
> multiples and the consequences can vary to a dramatic production bug, a
> failed CI 1% of the time, or to a useless test assertion.

One way I can think of doing this is write a script that walks through
your tables in the test db and does an UPDATE across the rows. It is
going to add time to your tests, but then I believe that is going to be
the case for anything you do. Or you could look at something I have
never tried, fuzzy testing. As a starting point:

https://www.guru99.com/fuzz-testing.html

Maybe other folks have suggestions on tools you could use for fuzzy
testing.

>
>
> *Peter*:
>
> It might be an interesting exercise to implement this as a post-parsing
> hook.
>
> I known nothing about that, but that sounds interesting, do you have any
> documentation pointer to help me implement that?
>
>
>
> On Wed, Jul 24, 2019 at 10:36 PM Peter Eisentraut
> <peter(dot)eisentraut(at)2ndquadrant(dot)com
> <mailto:peter(dot)eisentraut(at)2ndquadrant(dot)com>> wrote:
>
> On 2019-07-23 17:43, Cyril Champier wrote:
> > 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.
>
> It might be an interesting exercise to implement this as a post-parsing
> hook.
>
> --
> Peter Eisentraut http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com