Rails Model - Update Nested Key/Value in JSON

Question

I have a model with the following table format:

string  "name"
integer "line_id"
json    "filters"

Where the filters field contains a json object with nested keys. I want to modify a specific key without overwriting the rest of the json.

Currently, the json object stored in filters looks like

{
  "ext": {"name": "filter", "id": 3},
  "int": {"name": "numb", "id": 1}
}

I'm trying to update int.name 's value to "remove" without modifying the rest of the json object.

If I do the following, it'll simply overwrite the entire json object instead of modifying that specific key:

Model.where("filters->>'int'->>'name' IS NOT NULL").update(
  filters: {
    int: {
      name: "remove"
    }
  }
)

How can I simply update that one key with the path int.name while keeping the rest of the attributes the same?

Answer 1

which version of rails are you using? if you are using rails 5, you should be able to

m = Model.where("filters->>'int'->>'name' IS NOT NULL").first
m.filters['name'] = 'remove'
m.save

this will leave the existing hash keys in place.

I think with rails 4, you need a json serializer on the field, but should work the same way once you have the serializer, i believe.

Answer 2

How about something like this

models = Model.where("filters->>'int'->>'name' IS NOT NULL")
  .each_with_object({}) do |m,obj|
    # credit to mudasobwa for the tap usage 
    obj[m.id] = {filters: m.filters.tap { |h| h['int']['name'] = 'remove' } }
  end 
Model.update(models.keys,models.values)

I have never used a json column so I am unsure if the anticipated value is meant to be JSON or a Hash that will be converted to JSON before insertion but the update statement will be akin to

Model.update([1],[{
         "ext"=> {"name"=> "filter", "id"=> 3},
         "int"=> {"name"=> "remove", "id"=> 1}
       }])

This uses ActiveRecord::Relation#update where the first Array is the ids to update and the second Array is the new values to associate with those ids.