[#467] Update updated_at automatically

#467

migrations/20170123121324_add_trigger_for_updated_at.js

@@ -0,0 +1,36 @@
+'use strict';
+
+const Promise = require('bluebird');
+
+const tablesWithUpdatedAt = ['users', 'data_contributions'];
+
+exports.up = (knex) => (
+  knex.raw(
+    `CREATE FUNCTION set_updated_at()
+      RETURNS TRIGGER
+      LANGUAGE plpgsql
+    AS $$
+    BEGIN
+      NEW.updated_at := now();
+      RETURN NEW;
+    END;
+    $$;`
+  ).then(() =>
+     Promise.map(tablesWithUpdatedAt, (table) =>
+      knex.raw(
+        `CREATE TRIGGER ${table}_set_updated_at
+        BEFORE UPDATE ON ${table}
+        FOR EACH ROW EXECUTE PROCEDURE set_updated_at();`
+      )
+    )
+  )
+);
+
+exports.down = (knex) => (
+   Promise.map(tablesWithUpdatedAt, (table) =>
+    knex.raw(`DROP TRIGGER ${table}_set_updated_at ON ${table};`)
+  ).then(() =>
+    knex.raw('DROP FUNCTION set_updated_at();')
+  )
+);
+