json

select
  info ->> 'customer' customer
  , info -> 'items' ->> 'product' product
from
  orders

json_object

Возвращает json объект

select
  json_object(
    array_agg("id")::text[]
    , array_agg("name")::text[]
  )
from
  "cities"

/*
  {
    "1": "Moscow",
    "2": "Kazan"
  }
*/