Rails calling Postgresql method?

Question

PostgreSQL

I need to call a postgres method from rails.

categories = Entity.joins(:language, :category).
        select("coalesce('entities.short_descr', 'categories.short_descr')").
        where('languages.code = ?', 'en')

render json: {status: 'ok', categories: categories}

it doesn't work, returns

{"status":"ok","categories":[{"coalesce":"entities.short_descr","id":null}]}

How to do it right?

Answer 1

Find By SQL ?

Answer 2

....select("coalesce('entities.short_descr', 'categories.short_descr') as short_descr, entities.* ")....

Answer 3

Maybe so?

t1, t2 = [Entity.arel_table .....
a = Arel::Nodes::NamedFunction.new('coalesce', [t1[:short_descr], t2[:short_descr]]).as('descr')
Entity.select(a).....