removed default isolation level for transaction (#5915)

changelog.md

@@ -9,6 +9,7 @@
 - [FIXED] `BIGINT` gets truncated [#5176](https://github.com/sequelize/sequelize/issues/5176)
 - [FIXED] Trigger afterCreate hook after all nested includes (for hasMany or belongsToMany associations) have been created to be consistent with hasOne.
 - [REMOVED] Support for `pool:false`
+- [REMOVED] Default transaction isolation level [#5094](https://github.com/sequelize/sequelize/issues/5094)
 
 ## BC breaks:
 - `hookValidate` removed in favor of `validate` with `hooks: true | false`. `validate` returns a promise which is rejected if validation fails
@@ -18,6 +19,7 @@
 - `$notIn: []` will now match all rows instead of none
 - (MySQL) `BIGINT` now gets converted to string when number is too big
 - Removed support for `pool:false`, if you still want to use single connection set `pool.max` to `1`
+- Removed default `REPEATABLE_READ` transaction isolation, use config option to explicitly set it
 
 # 3.23.2
 - [FIXED] Type validation now works with non-strings due to updated validator@5.0.0 [#5861](https://github.com/sequelize/sequelize/pull/5861)

lib/query-interface.js

@@ -851,7 +851,8 @@ QueryInterface.prototype.setIsolationLevel = function(transaction, value, option
   if (!transaction || !(transaction instanceof Transaction)) {
     throw new Error('Unable to set isolation level for a transaction without transaction object!');
   }
-  if (transaction.parent) {
+
+  if (transaction.parent || !value) {
     // Not possible to set a seperate isolation level for savepoints
     return Promise.resolve();
   }

lib/sequelize.js

@@ -86,7 +86,7 @@ var url = require('url')
  * @param {Function} [options.pool.validateConnection] A function that validates a connection. Called with client. The default function checks that client is an object, and that its state is not disconnected
  * @param {Boolean}  [options.quoteIdentifiers=true] Set to `false` to make table names and attributes case-insensitive on Postgres and skip double quoting of them.
  * @param {String}   [options.transactionType='DEFERRED'] Set the default transaction type. See `Sequelize.Transaction.TYPES` for possible options. Sqlite only.
- * @param {String}   [options.isolationLevel='REPEATABLE_READ'] Set the default transaction isolation level. See `Sequelize.Transaction.ISOLATION_LEVELS` for possible options.
+ * @param {String}   [options.isolationLevel] Set the default transaction isolation level. See `Sequelize.Transaction.ISOLATION_LEVELS` for possible options.
  * @param {Object}   [options.retry] Set of flags that control when a query is automatically retried.
  * @param {Array}    [options.retry.match] Only retry a query if the error matches one of these strings.
  * @param {Integer}  [options.retry.max] How many times a failing query is automatically retried.  Set to 0 to disable retrying on SQL_BUSY error.
@@ -167,7 +167,7 @@ var Sequelize = function(database, username, password, options) {
     hooks: {},
     retry: {max: 5, match: ['SQLITE_BUSY: database is locked']},
     transactionType: Transaction.TYPES.DEFERRED,
-    isolationLevel: Transaction.ISOLATION_LEVELS.REPEATABLE_READ,
+    isolationLevel: null,
     databaseVersion: 0,
     typeValidation: false,
     benchmark: false
@@ -1261,7 +1261,7 @@ Sequelize.where = Sequelize.condition = Sequelize.prototype.condition = Sequeliz
  * @param {Object}   [options={}]
  * @param {Boolean}  [options.autocommit=true]
  * @param {String}   [options.type='DEFERRED'] See `Sequelize.Transaction.TYPES` for possible options. Sqlite only.
- * @param {String}   [options.isolationLevel='REPEATABLE_READ'] See `Sequelize.Transaction.ISOLATION_LEVELS` for possible options
+ * @param {String}   [options.isolationLevel] See `Sequelize.Transaction.ISOLATION_LEVELS` for possible options
  * @param {Function} [options.logging=false] A function that gets executed while running the query to log the sql.
  * @return {Promise}
  * @fires error If there is an uncaught error during the transaction