The commit includes three changes that work to allow us to "seed" the
randomization. When using the same seed, and randomizer should/must
return the same sequence of numbers.
First, I added the "seed" parameter to the variant query. If you want
the same sequence of random numbers from query to query, pass the same
seed. Otherwise, we'll use a Ruby generated random seed.
Second, I added a virtual column to the virtual `article_relevancies`
table. If you provide a seed, and call the query twice, the first row
in each of `article_relevancies` will have the same `randomized_value`,
likewise the second row, etc.
Third, I amended the existing `order_by_lever` that had a `RANDOM()`
postgresql function call. I replaced that with the `randomized_value`
which is computed based on the provided seed.
Fundamentally the idea is to allow for randomness but introduce possible
repeatability; a hard thing considering that some of the inner selection
criteria is not fixed (e.g. number of reactions can change from moment
to moment).
I wrote a [complimentary blog post][1] to further explain what's
happening.
Related to forem/forem#17826
[1]:https://takeonrules.com/2022/06/03/adding-reproducible-randomization-to-sql-queries/
2e19ea9255