Added feature to alter tables on sync. Fixes #537 (#7230)

* Added feature to alter tables on sync. Fixes #537

* Added an entry to future in changelog

* Added integration test for syncing with alter

* Fixed tests and model with sqlite and psql

* Updated docs and updated some code style

* Updated test.sync.js to use let instead of var

* Changed all vars to lets and replaced anonymous functions with arrow functions

* Added back some anonymous functions to use scope and fixed more coding style

* Updated code style again - removed binds and nested then's

* Updated changelog; renamed and improved tests; Added option to comment

* Changed debug vars to consts

* Switched changes to const

* Added some missing semi-colons

changelog.md

 # Future
+- [ADDED] `options.alter` to sequelize.sync() to alter existing tables.[#537](https://github.com/sequelize/sequelize/issues/537)
 - [ADDED] Ability to run transactions on a read-replica by marking transactions as read only [#7323](https://github.com/sequelize/sequelize/issues/7323)
 - [FIXED] Show a reasonable message when using renameColumn with a missing column  [#6606](https://github.com/sequelize/sequelize/issues/6606)
 - [PERFORMANCE] more efficient array handing for certain large queries [#7175](https://github.com/sequelize/sequelize/pull/7175)

docs/api/sequelize.md

@@ -789,6 +789,7 @@ Sync all defined models to the DB.
 | [options.schema='public'] | String | The schema that the tables should be created in. This can be overriden for each table in sequelize.define |
 | [options.searchPath=DEFAULT] | String | An optional parameter to specify the schema search_path (Postgres only) |
 | [options.hooks=true] | Boolean | If hooks is true then beforeSync, afterSync, beforBulkSync, afterBulkSync hooks will be called |
+| [options.alter=false] | Boolean | Alters tables to fit models. Not recommended for production use. Deletes data in columns that were removed or had their type changed in the model. |
 
 
 ***

lib/model.js

@@ -1111,6 +1111,27 @@ class Model {
       }
     })
     .then(() => this.QueryInterface.createTable(this.getTableName(options), attributes, options, this))
+    .then(() => {
+      if (options.alter) {
+        return this.QueryInterface.describeTable(this.getTableName(options))
+          .then(columns => {
+            const changes = []; // array of promises to run
+            _.each(attributes, (columnDesc, columnName) => {
+              if (!columns[columnName]) {
+                changes.push(() => this.QueryInterface.addColumn(this.getTableName(options), columnName, attributes[columnName]));
+              }
+            });
+            _.each(columns, (columnDesc, columnName) => {
+              if (!attributes[columnName]) {
+                changes.push(() => this.QueryInterface.removeColumn(this.getTableName(options), columnName, options));
+              } else if (!attributes[columnName].primaryKey) {
+                changes.push(() => this.QueryInterface.changeColumn(this.getTableName(options), columnName, attributes[columnName]));
+              }
+            });
+            return changes.reduce((p, fn) => p.then(fn), Promise.resolve());
+          });
+        }
+    })
     .then(() => this.QueryInterface.showIndex(this.getTableName(options), options))
     .then(indexes => {
       // Assign an auto-generated name to indexes which are not named by the user

lib/sequelize.js

@@ -678,6 +678,7 @@ class Sequelize {
    * @param {String} [options.schema='public'] The schema that the tables should be created in. This can be overriden for each table in sequelize.define
    * @param  {String} [options.searchPath=DEFAULT] An optional parameter to specify the schema search_path (Postgres only)
    * @param {Boolean} [options.hooks=true] If hooks is true then beforeSync, afterSync, beforBulkSync, afterBulkSync hooks will be called
+   * @param {Boolean} [options.alter=false] Alters tables to fit models. Not recommended for production use. Deletes data in columns that were removed or had their type changed in the model.
    * @return {Promise}
    */
   sync(options) {

test/integration/model/sync.test.js

+'use strict';
+
+/* jshint -W030 */
+/* jshint -W110 */
+const chai = require('chai')
+  , Sequelize = require('../../../index')
+  , expect = chai.expect
+  , Support = require(__dirname + '/../support');
+
+describe(Support.getTestDialectTeaser('Model'), function() {
+  describe('sync', function() {
+    beforeEach(function() {
+      this.testSync = this.sequelize.define('testSync', {
+        dummy: Sequelize.STRING
+      });
+      return this.testSync.drop();
+    });
+
+    it('should remove a column if it exists in the databases schema but not the model', function() {
+      const User = this.sequelize.define('testSync', {
+        name: Sequelize.STRING,
+        age: Sequelize.INTEGER
+      });
+      return this.sequelize.sync()
+        .then(() => {
+          this.sequelize.define('testSync', {
+            name: Sequelize.STRING
+          });
+        })
+        .then(() => this.sequelize.sync({alter: true}))
+        .then(() => User.describe())
+        .then(data => {
+          expect(data).to.not.have.ownProperty('age');
+          expect(data).to.have.ownProperty('name');
+        });
+    });
+
+    it('should add a column if it exists in the model but not the database', function() {
+      const testSync = this.sequelize.define('testSync', {
+        name: Sequelize.STRING
+      });
+      return this.sequelize.sync()
+        .then(() => this.sequelize.define('testSync', {
+            name: Sequelize.STRING,
+            age: Sequelize.INTEGER
+          }))
+        .then(() => this.sequelize.sync({alter: true}))
+        .then(() => testSync.describe())
+        .then(data => expect(data).to.have.ownProperty('age'));
+    });
+
+    it('should change a column if it exists in the model but is different in the database', function() {
+      const testSync = this.sequelize.define('testSync', {
+        name: Sequelize.STRING,
+        age: Sequelize.INTEGER
+      });
+      return this.sequelize.sync()
+        .then(() => this.sequelize.define('testSync', {
+            name: Sequelize.STRING,
+            age: Sequelize.STRING
+          }))
+        .then(() => this.sequelize.sync({alter: true}))
+        .then(() => testSync.describe())
+        .then(data => {
+          expect(data).to.have.ownProperty('age');
+          expect(data.age.type).to.have.string('CHAR'); // CHARACTER VARYING, VARCHAR(n)
+        });
+    });
+
+    it('should not alter table if data type does not change', function() {
+      const testSync = this.sequelize.define('testSync', {
+        name: Sequelize.STRING,
+        age: Sequelize.STRING
+      });
+      return this.sequelize.sync()
+        .then(() => testSync.create({name: 'test', age: '1'}))
+        .then(() => this.sequelize.sync({alter: true}))
+        .then(() => testSync.findOne())
+        .then(data => {
+          expect(data.dataValues.name).to.eql('test');
+          expect(data.dataValues.age).to.eql('1');
+        });
+    });
+  });
+});