如何按postgres数组中的多个ID分组

Question

I am trying to select a row based upon a count of the nubmer of items in a Postgres array (represented as a text field in Postgres 9.4) and be able to select / group in Rails 4.2

I have the following tables:

 queryable_id | liked_count | users_who_like_ids 
--------------+-------------+--------------------
         2376 |           3 | {1,80,78,101, 188}
        18771 |           1 | {78,101, 123,125}
         1790 |           1 | {78}
         2257 |           1 | {78}

For example, I'd like to say select the and order by user_who_like_ids like

select * from items group by count(users_who_like_ids) where users_who_like_ids include (78,123,125)

How would I make this query? Would this type of query be supported in rails?

edit 1

here is the users_who_like_ids

 users_who_like_ids      | text[]                      | default '{}'::text[]

edit 2

It looks like this kinda works:

select queryable_id, liked_count, users_who_like_ids  from  queryables where users_who_like_ids  @> ARRAY['1','80'];

but this requires both 1 and 80

Answer 1

I think, you are looking for array_length()

select
  *
from 
  items
where
  users_who_like_ids @> ARRAY[78,123,125]
group by
  array_length(users_who_like_ids) 

Note, that the where clause always belongs for the group by clause.