changelog: add release note v2.1.4 (pingcap#9312)

CHANGELOG.md

@@ -1,6 +1,26 @@
 # TiDB Changelog
 All notable changes to this project will be documented in this file. See also [Release Notes](https://github.com/pingcap/docs/blob/master/releases/rn.md), [TiKV Changelog](https://github.com/tikv/tikv/blob/master/CHANGELOG.md) and [PD Changelog](https://github.com/pingcap/pd/blob/master/CHANGELOG.md).
 
+## [2.1.4] 2019-02-15
+
+### SQL Optimizer/Executor
+
+* Fix the issue that the `VALUES` function does not handle the FLOAT type correctly [#9223](https://github.com/pingcap/tidb/pull/9223)
+* Fix the wrong result issue when casting Float to String in some cases [#9227](https://github.com/pingcap/tidb/pull/9227)
+* Fix the wrong result issue of the `FORMAT` function in some cases [#9235](https://github.com/pingcap/tidb/pull/9235)
+* Fix the panic issue when handling the Join query in some cases [#9264](https://github.com/pingcap/tidb/pull/9264)
+* Fix the issue that the `VALUES` function does not handle the ENUM type correctly [#9280](https://github.com/pingcap/tidb/pull/9280)
+* Fix the wrong result issue of `DATE_ADD` / `DATE_SUB` in some cases [#9284](https://github.com/pingcap/tidb/pull/9284)
+
+### Server
+
+* Optimize the "reload privilege success" log and change it to the DEBUG level [#9274](https://github.com/pingcap/tidb/pull/9274)
+
+### DDL
+
+* Change `tidb_ddl_reorg_worker_cnt` and `tidb_ddl_reorg_batch_size` to global variables [#9134](https://github.com/pingcap/tidb/pull/9134)
+* Fix the bug caused by adding an index to a generated column in some abnormal conditions [#9289](https://github.com/pingcap/tidb/pull/9289)
+
 ## [2.1.3] 2019-01-25
 
 ### SQL Optimizer/Executor