CHANGELOG: Add changelog for 2.0.5 (#7005)

Author: shenli

CHANGELOG.md

@@ -2,6 +2,28 @@
 
 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/pingcap/tikv/blob/master/CHANGELOG.md) and [PD changelog](https://github.com/pingcap/pd/blob/master/CHANGELOG.md).
 
+## [2.0.5] - 2018-07-06
+### New Features
+  - Add the `tidb_disable_txn_auto_retry` system variable which is used to disable the automatic retry of transactions [#6877](https://github.com/pingcap/tidb/pull/6877)
+### Improvements
+  - Optimize the cost calculation of `Selection` to make the result more accurate [#6989](https://github.com/pingcap/tidb/pull/6989)
+  - Select the query condition that completely matches the unique index or the primary key as the query path directly [#6966](https://github.com/pingcap/tidb/pull/6966)
+  - Execute necessary cleanup when failing to start the service [#6964](https://github.com/pingcap/tidb/pull/6964)
+  - Handle `\N` as NULL in the `Load Data` statement [#6962](https://github.com/pingcap/tidb/pull/6962)
+  - Optimize the code structure of CBO [#6953](https://github.com/pingcap/tidb/pull/6953)
+  - Report the monitoring metrics earlier when starting the service [#6931](https://github.com/pingcap/tidb/pull/6931)
+  - Optimize the format of slow queries by removing the line breaks in SQL statements and adding user information [#6931](https://github.com/pingcap/tidb/pull/6931)
+  - Support multiple asterisks in comments [#6931](https://github.com/pingcap/tidb/pull/6931)
+### Bug Fixes
+  - Fix the issue that `KILL QUERY` always requires SUPER privilege [#6931](https://github.com/pingcap/tidb/pull/6931)
+  - Fix the issue that users might fail to login when the number of users exceeds 1024 [#6986](https://github.com/pingcap/tidb/pull/6986)
+  - Fix an issue about inserting unsigned `float`/`double` data [#6940](https://github.com/pingcap/tidb/pull/6940)
+  - Fix the compatibility of the `COM_FIELD_LIST` command to resolve the panic issue in some MariaDB clients [#6929](https://github.com/pingcap/tidb/pull/6929)
+  - Fix the `CREATE TABLE IF NOT EXISTS LIKE` behavior [#6928](https://github.com/pingcap/tidb/pull/6928)
+  - Fix an issue in the process of TopN pushdown [#6923](https://github.com/pingcap/tidb/pull/6923)
+  - Fix the ID record issue of the currently processing row when an error occurs in executing `Add Index` [#6903](https://github.com/pingcap/tidb/pull/6903)
+
+
 ## [2.0.4] - 2018-06-15
 ### New Features
   - Support the `ALTER TABLE t DROP COLUMN a CASCADE` syntax
@@ -260,4 +282,4 @@ Only TiKV has this release
 * Support more `SQL_MODE`
 * Optimize the `Load Data` performance to increase the speed by 10 times
 * Optimize the `Use Database` performance
-* Support statistics on the memory usage of physical operators
+* Support statistics on the memory usage of physical operators