README, releases: add 2.1.5 release notes (pingcap#924)

README.md

@@ -167,6 +167,7 @@
 - [Frequently Asked Questions (FAQ)](FAQ.md)
 - [TiDB Best Practices](https://pingcap.com/blog/2017-07-24-tidbbestpractice/)
 + [Releases](releases/rn.md)
+  - [2.1.5](releases/2.1.5.md)
   - [2.1.4](releases/2.1.4.md)
   - [2.1.3](releases/2.1.3.md)
   - [3.0 Beta](releases/3.0beta.md)

releases/2.1.5.md

@@ -0,0 +1,54 @@
+---
+title: TiDB 2.1.5 Release Notes
+category: Releases
+---
+
+# TiDB 2.1.5 Release Notes
+
+On February 28, 2019, TiDB 2.1.5 is released. The corresponding TiDB-Ansible 2.1.5 is also released. Compared with TiDB 2.1.4, this release has greatly improved the stability, the SQL optimizer, statistics, and the execution engine.
+
+## TiDB
+
++ SQL Optimizer/Executor
+    - Make `SHOW CREATE TABLE` do not print the column charset information when the charset information of a column is the same with that of a table, to improve the compatibility of `SHOW CREATE TABLE` with MySQL [#9306](https://github.com/pingcap/tidb/pull/9306)
+    - Fix the panic or the wrong result of the `Sort` operator in some cases by extracting `ScalarFunc` from `Sort` to a `Projection` operator for computing to simplify the computing logic of `Sort` [#9319](https://github.com/pingcap/tidb/pull/9319)
+    - Remove the sorting field with constant values in the `Sort` operator [#9335](https://github.com/pingcap/tidb/pull/9335), [#9440](https://github.com/pingcap/tidb/pull/9440)
+    - Fix the data overflow issue when inserting data into an unsigned integer column [#9339](https://github.com/pingcap/tidb/pull/9339)
+    - Set `cast_as_binary` to `NULL` when the length of the target binary exceeds `max_allowed_packet` [#9349](https://github.com/pingcap/tidb/pull/9349)
+    - Optimize the constant folding process of `IF` and `IFNULL` [#9351](https://github.com/pingcap/tidb/pull/9351)
+    - Optimize the index selection of TiDB using skyline pruning to improve the stability of simple queries [#9356](https://github.com/pingcap/tidb/pull/9356)
+    - Support computing the selectivity of the `DNF` expression [#9405](https://github.com/pingcap/tidb/pull/9405)
+    - Fix the wrong SQL query result of `!=ANY()` and `=ALL()` in some cases [#9403](https://github.com/pingcap/tidb/pull/9403)
+    - Fix the panic or the wrong result when the Join Key types of two tables on which  the `Merge Join` operation is performed are different [#9438](https://github.com/pingcap/tidb/pull/9438)
+    - Fix the issue that the result of the `RAND()` function is not compatible with MySQL [#9446](https://github.com/pingcap/tidb/pull/9446)
+    - Refactor the logic of `Semi Join` processing `NULL` and the empty result set to get the correct result and improve the compatibility with MySQL [#9449](https://github.com/pingcap/tidb/pull/9449)
++ Server
+    - Add the `tidb_constraint_check_in_place` system variable to check the data uniqueness constraint when executing the `INSERT` statement [#9401](https://github.com/pingcap/tidb/pull/9401)
+    - Fix the issue that the value of the `tidb_force_priority` system variable is different from that set in the configuration file [#9347](https://github.com/pingcap/tidb/pull/9347)
+    - Add the `current_db` field in general logs to print the name of the currently used database [#9346](https://github.com/pingcap/tidb/pull/9346)
+    - Add an HTTP API of obtaining the table information with the table ID [#9408](https://github.com/pingcap/tidb/pull/9408)
+    - Fix the issue that `LOAD DATA` loads incorrect data in some cases [#9414](https://github.com/pingcap/tidb/pull/9414)
+    - Fix the issue that it takes a long time to build a connection between the MySQL client and TiDB in some cases [#9451](https://github.com/pingcap/tidb/pull/9451)
++ DDL
+    - Fix some issues when canceling the `DROP COLUMN` operation [#9352](https://github.com/pingcap/tidb/pull/9352)
+    - Fix some issues when canceling the `DROP` or `ADD` partitioned table operation [#9376](https://github.com/pingcap/tidb/pull/9376)
+    - Fix the issue that `ADMIN CHECK TABLE` mistakenly reports the data index inconsistency in some cases [#9399](https://github.com/pingcap/tidb/pull/9399)
+    - Fix the time zone issue of the `TIMESTAMP` default value [#9108](https://github.com/pingcap/tidb/pull/9108)
+
+## PD
+
+- Provide the `exclude_tombstone_stores` option in the `GetAllStores` interface to remove the Tombstone store from the returned result [#1444](https://github.com/pingcap/pd/pull/1444)
+
+## TiKV
+
+- Fix the issue that Importer fails to import data in some cases [#4223](https://github.com/tikv/tikv/pull/4223)
+- Fix the `KeyNotInRegion` error in some cases [#4125](https://github.com/tikv/tikv/pull/4125)
+- Fix the panic issue caused by Region merge in some cases [#4235](https://github.com/tikv/tikv/pull/4235)
+- Add the detailed `StoreNotMatch` error message [#3885](https://github.com/tikv/tikv/pull/3885)
+
+## Tools
+
++ Lightning 
+    - Do not report an error or exit when a Tombstone store exists in the cluster [#4223](https://github.com/tikv/tikv/pull/4223)
++ TiDB-Binlog
+    - Update the DDL binlog replication plan to guarantee the correctness of DDL event replication [#9304](https://github.com/pingcap/tidb/issues/9304)

releases/rn.md

@@ -5,6 +5,7 @@ category: release
 
 # TiDB Release Notes
 
+- [2.1.5](../releases/2.1.5.md)
 - [2.1.4](../releases/2.1.4.md)
 - [2.1.3](../releases/2.1.3.md)
 - [3.0 Beta](../releases/3.0beta.md)