Search ranking order

[belst]

tags := array of tags of model (videos, playlists)
query := array of tags of searchquery

find:

SELECT * FROM model_table WHERE tags && query;

&& = overlap operator.

ordering:

need: union and intersection cardinality functions. (here: card_intersect(arr1, arr2) and card_union(arr1, arr2))

ORDER BY card_intersect(arr1, arr2) / card_union(arr1, arr2) DESC;

union must not be empty (just drop empty search queries.)