Bulk update for devices when type structure change

[andreareginato]

One of the performance issues in Lelylan lies in the fact that when the type changes its properties, all devices properties needs to be updated (this doesn't smell good). This is a bad practice as the type should be living by its own and never be changed, but right now this could happen.

To solve this problem we experimented one shot query on mongodb, which we finally found out not being possible for now, as there is a BUG that will be solved only on version 2.3.2 (at the moment of writing we are at v2.2.0). Here is the code that should work for future improvements. For now we will simply work one record at time.

db.devices.find({ type_id: ObjectId("50bdcf90d033a95079000010"), 'properties.property_id': ObjectId("50bdcf90d033a95079000002") })

// update a value in the embedded document
db.devices.update(
   { type_id: ObjectId("50bdcf90d033a95079000010"), 'properties.property_id': ObjectId("50bdcf90d033a95079000002") },
   { $set: { 'properties.$.value': 'UPDATED' } },
   { multi: true }
)

// add a new embedded document 
db.devices.update(
   { type_id: ObjectId("50bdcf90d033a95079000010"), 'properties.property_id':  },
   { $push: { 'properties': { property_id: ObjectId("50bdcf90d033a95079000002"), value: 'ON' } } },
   { multi: true }
)

// remove an embedded document
db.devices.update(
   { type_id: ObjectId("50bdcf90d033a95079000010"), 'properties.property_id':  },
   { $pull: { 'properties': { property_id: ObjectId("50bdcf90d033a95079000002") } } },
   { multi: true }
)

Then, to add the code to MongoID you only need to call the collection method.

Device.collection.update(
   { type_id: Moped::BSON::ObjectId("50bdcf90d033a95079000010"), "properties.property_id" => Moped::BSON::ObjectId("50bdcf90d033a95079000002") },
   { "$set" => { "properties.$.value": "UPDATED" } },
   { multi: true }
)

To create the test suite run the following commands (a type must exist).

require 'factory_girl_rails'
u = FactoryGirl.create :user
type_id = Type.all.first.id
FactoryGirl.create :device, type:"http://api.lelylan.com/types/50bdcf90d033a95079000010", resource_owner_id: u.id, creator_id: u.id
FactoryGirl.create :device, type:"http://api.lelylan.com/types/50bdcf90d033a95079000010", resource_owner_id: u.id, creator_id: u.id
FactoryGirl.create :device, type:"http://api.lelylan.com/types/50bdcf90d033a95079000010", resource_owner_id: u.id, creator_id: u.id
Device.all.map(&:properties).map(&:first).map(&:value)

Learn more reading

• MongoDB update documentation
• MongoDB dolar operator