introduces migrations

lib/neo4j/migration.rb

@@ -0,0 +1,62 @@
+module Neo4j
+  class Migration
+    class AddIdProperty < Neo4j::Migration
+      attr_reader :models_filename
+
+      def initialize
+        @models_filename = File.join(Rails.root.join('db', 'neo4j-migrate'), 'add_id_property.yml')
+      end
+
+      def migrate
+        models = ActiveSupport::HashWithIndifferentAccess.new(YAML.load_file(models_filename))[:models]
+        puts "This task will add an ID Property every node in the given file."
+        puts "It may take a significant amount of time, please be patient."
+        models.each do |model|
+          puts "Adding IDs to #{model}"
+          add_ids_to model.constantize
+        end
+      end
+
+      def setup
+        FileUtils.mkdir_p("db/neo4j-migrate")
+        unless File.file?(models_filename)
+          File.open(models_filename, 'w') do |file| 
+            file.write("# Provide models to which IDs should be added.\n# It will only modify nodes that do not have IDs. There is no danger of overwriting data.\n# models: [Student,Lesson,Teacher,Exam]\nmodels: []")
+          end
+        end
+      end
+
+      private
+
+      def add_ids_to(model)
+        label = model.mapped_label_name
+        property = model.primary_key
+        total = 1
+
+        until total == 0
+          total = Neo4j::Session.query("MATCH (n:`#{label}`) WHERE NOT has(n.#{property}) RETURN COUNT(n) as ids").first.ids
+          return if total == 0
+          to_set = total > 900 ? 900 : total
+          new_ids = [].tap do | ids_array|
+                      to_set.times { ids_array.push "'#{new_id_for(model)}'" }
+                    end
+          Neo4j::Session.query("MATCH (n:`#{label}`) WHERE NOT has(n.#{property})
+            with COLLECT(n) as nodes, [#{new_ids.join(',')}] as ids
+            FOREACH(i in range(0,#{to_set - 1})| 
+              FOREACH(node in [nodes[i]]|
+                SET node.#{property} = ids[i]))
+            RETURN distinct(true)
+            limit #{to_set}")
+        end
+      end
+
+      def new_id_for(model)
+        if model.id_property_info[:type][:auto]
+          SecureRandom::uuid
+        else
+          model.new.send(model.id_property_info[:type][:on])
+        end
+      end
+    end
+  end
+end

lib/neo4j/tasks/rails.rb

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+require 'neo4j/migration'
+
+namespace :neo4j do
+  desc "Run a script against the database to perform system-wide changes"
+  task :migrate, [:task_name, :subtask] => :environment do |_, args|
+    migration_task = args[:task_name]
+    task_name_constant = migration_task.split('_').map { |word| word.capitalize }.join('')
+    begin
+    migration_class = "Neo4j::Migration::#{task_name_constant}".constantize
+    rescue NameError
+      load File.join(Rails.root.join('db', 'neo4j-migrate'), "#{migration_task}.rb")
+      migration_class = "#{task_name_constant}".constantize
+    end
+    migration = migration_class.new
+
+    subtask = args[:subtask]
+    if subtask
+      migration.send(subtask)
+    else
+      migration.migrate
+    end
+  end
+end