Postgres JSON field update with ActiveRecord

Question

What's the best way to use update with a json field. I'd like my JSON field to accept new keys or update existing keys, but not overwrite the entire field. ActiveRecord does a nice job of just updating fields that changed, but I don't understand how to apply that to the sub-fields in the json record...

it 'can update settings with a plain object' do
  integration = Integration.create(
    name: 'Name',
    json_settings: {
      key1: 1,
      key2: 2
    }
  )
  integration.update(
    settings: { key2: 2 }
  )
  // json_settings is now { "key2": 3 } but I want
  // { "key1": 1, "key2": 3 } 
  expect(integration.json_settings['key1']).to eq('1') // fails
end

Arup Rakshit · Accepted Answer · 2015-03-27 18:40:45Z

7

Your code should look like:

it 'can update settings with a plain object' do
  integration = Integration.create(
    name: 'Name',
    json_settings: {
      key1: 1,
      key2: 2
    }
  )
  integration.json_settings = integration.json_settings.merge { key2: 3 }
  integration.save
  expect(integration.json_settings['key1']).to eq(1)
end

edited Mar 27, 2015 at 18:40

answered Mar 27, 2015 at 18:32

Arup Rakshit

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6 Comments

typeoneerror Over a year ago

ok, that was what I was going to do, but wasn't sure if there was any rails way of updating that field with a merge by default.

jrochkind Over a year ago

yes, I'm curious if there is a way to get AR to do an atomic update too. If not when this was asked, now in AR 5.2. This answer doesn't actually answer the question.

Arup Rakshit Over a year ago

@jrochkind The question was not related to any atomic update either.

jrochkind Over a year ago

"accept new keys or update existing keys, but not overwrite the entire field" -- "atomic update" may not be the right word for this, but that's one thing I've seen it called. This answer leads to AR code that updates the entire hash with AR's in-memory version.

Arup Rakshit Over a year ago

Yeah the answer did it correct way. I think you are thinking too deep on this which is not needed. There is nothing about atomicity at least in this question. What OP asked, not to remove old keys/values, rather do a merge operation.

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