1 files changed, 124 insertions, 0 deletions
diff --git a/db/post_migrate/20180223124427_build_user_interacted_projects_table.rb b/db/post_migrate/20180223124427_build_user_interacted_projects_table.rb
new file mode 100644
index 00000000000..5e729b1aa53
--- /dev/null
+++ b/db/post_migrate/20180223124427_build_user_interacted_projects_table.rb
@@ -0,0 +1,124 @@
+class BuildUserInteractedProjectsTable < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    if Gitlab::Database.postgresql?
+      PostgresStrategy.new
+    else
+      MysqlStrategy.new
+    end.up
+
+    unless index_exists?(:user_interacted_projects, [:project_id, :user_id])
+      add_concurrent_index :user_interacted_projects, [:project_id, :user_id], unique: true
+    end
+
+    unless foreign_key_exists?(:user_interacted_projects, :user_id)
+      add_concurrent_foreign_key :user_interacted_projects, :users, column: :user_id, on_delete: :cascade
+    end
+
+    unless foreign_key_exists?(:user_interacted_projects, :project_id)
+      add_concurrent_foreign_key :user_interacted_projects, :projects, column: :project_id, on_delete: :cascade
+    end
+  end
+
+  def down
+    execute "TRUNCATE user_interacted_projects"
+
+    if foreign_key_exists?(:user_interacted_projects, :user_id)
+      remove_foreign_key :user_interacted_projects, :users
+    end
+
+    if foreign_key_exists?(:user_interacted_projects, :project_id)
+      remove_foreign_key :user_interacted_projects, :projects
+    end
+
+    if index_exists_by_name?(:user_interacted_projects, 'index_user_interacted_projects_on_project_id_and_user_id')
+      remove_concurrent_index_by_name :user_interacted_projects, 'index_user_interacted_projects_on_project_id_and_user_id'
+    end
+  end
+
+  private
+
+  # Rails' index_exists? doesn't work when you only give it a table and index
+  # name. As such we have to use some extra code to check if an index exists for
+  # a given name.
+  def index_exists_by_name?(table, index)
+    indexes_for_table[table].include?(index)
+  end
+
+  def indexes_for_table
+    @indexes_for_table ||= Hash.new do |hash, table_name|
+      hash[table_name] = indexes(table_name).map(&:name)
+    end
+  end
+
+  def foreign_key_exists?(table, column)
+    foreign_keys(table).any? do |key|
+      key.options[:column] == column.to_s
+    end
+  end
+
+  class PostgresStrategy < ActiveRecord::Migration
+    include Gitlab::Database::MigrationHelpers
+
+    BATCH_SIZE = 100_000
+    SLEEP_TIME = 5
+
+    def up
+      with_index(:events, [:author_id, :project_id], name: 'events_user_interactions_temp', where: 'project_id IS NOT NULL') do
+        iteration = 0
+        records = 0
+        begin
+          Rails.logger.info "Building user_interacted_projects table, batch ##{iteration}"
+          result = execute <<~SQL
+            INSERT INTO user_interacted_projects (user_id, project_id)
+            SELECT e.user_id, e.project_id
+            FROM (SELECT DISTINCT author_id AS user_id, project_id FROM events WHERE project_id IS NOT NULL) AS e
+            LEFT JOIN user_interacted_projects ucp USING (user_id, project_id)
+            WHERE ucp.user_id IS NULL
+            LIMIT #{BATCH_SIZE}
+          SQL
+          iteration += 1
+          records += result.cmd_tuples
+          Rails.logger.info "Building user_interacted_projects table, batch ##{iteration} complete, created #{records} overall"
+          Kernel.sleep(SLEEP_TIME) if result.cmd_tuples > 0
+        rescue ActiveRecord::InvalidForeignKey => e
+          Rails.logger.info "Retry on InvalidForeignKey: #{e}"
+          retry
+        end while result.cmd_tuples > 0
+      end
+
+      execute "ANALYZE user_interacted_projects"
+
+    end
+
+    private
+
+    def with_index(*args)
+      add_concurrent_index(*args) unless index_exists?(*args)
+      yield
+    ensure
+      remove_concurrent_index(*args) if index_exists?(*args)
+    end
+  end
+
+  class MysqlStrategy < ActiveRecord::Migration
+    include Gitlab::Database::MigrationHelpers
+
+    def up
+      execute <<~SQL
+        INSERT INTO user_interacted_projects (user_id, project_id)
+        SELECT e.user_id, e.project_id
+        FROM (SELECT DISTINCT author_id AS user_id, project_id FROM events WHERE project_id IS NOT NULL) AS e
+        LEFT JOIN user_interacted_projects ucp USING (user_id, project_id)
+        WHERE ucp.user_id IS NULL
+      SQL
+    end
+  end
+
+end