Gab Social. All are welcome.

db/migrate/20170920024819_status_ids_to_timestamp_ids.rb

@@ -0,0 +1,32 @@
+class StatusIdsToTimestampIds < ActiveRecord::Migration[5.1]
+  def up
+    # Prepare the function we will use to generate IDs.
+    Rake::Task['db:define_timestamp_id'].execute
+
+    # Set up the statuses.id column to use our timestamp-based IDs.
+    ActiveRecord::Base.connection.execute(<<~SQL)
+      ALTER TABLE statuses
+      ALTER COLUMN id
+      SET DEFAULT timestamp_id('statuses')
+    SQL
+
+    # Make sure we have a sequence to use.
+    Rake::Task['db:ensure_id_sequences_exist'].execute
+  end
+
+  def down
+    # Revert the column to the old method of just using the sequence
+    # value for new IDs. Set the current ID sequence to the maximum
+    # existing ID, such that the next sequence will be one higher.
+
+    # We lock the table during this so that the ID won't get clobbered,
+    # but ID is indexed, so this should be a fast operation.
+    ActiveRecord::Base.connection.execute(<<~SQL)
+      LOCK statuses;
+      SELECT setval('statuses_id_seq', (SELECT MAX(id) FROM statuses));
+      ALTER TABLE statuses
+        ALTER COLUMN id
+        SET DEFAULT nextval('statuses_id_seq');
+    SQL
+  end
+end