README, releases: add releases notes for TiDB 2.1.2 (pingcap#824)

* README, releases: add releases notes for TiDB 2.1.2

* Update 2.1.2.md

README.md

@@ -158,6 +158,7 @@
 - [Frequently Asked Questions (FAQ)](FAQ.md)
 - [TiDB Best Practices](https://pingcap.com/blog/2017-07-24-tidbbestpractice/)
 + [Releases](releases/rn.md)
+  - [2.1.2](releases/2.1.2.md)
   - [2.0.10](releases/2.0.10.md)
   - [2.1.1](releases/2.1.1.md)
   - [2.1 GA](releases/2.1ga.md)

releases/2.1.2.md

@@ -0,0 +1,39 @@
+---
+title: TiDB 2.1.2 Release Notes
+category: Releases
+---
+
+# TiDB 2.1.2 Release Notes
+
+On December 22, 2018, TiDB 2.1.2 is released. The corresponding TiDB-Ansible 2.1.2 is also released. Compared with TiDB 2.1.1, this release has great improvement in system compatibility and stability.
+
+## TiDB
+
+- Make TiDB compatible with TiDB-Binlog of the Kafka version [#8747](https://github.com/pingcap/tidb/pull/8747)
+- Improve the exit mechanism of TiDB in a rolling update [#8707](https://github.com/pingcap/tidb/pull/8707)
+- Fix the panic issue caused by adding the index for the generated column in some cases [#8676](https://github.com/pingcap/tidb/pull/8676)
+- Fix the issue that the optimizer cannot find the optimal query plan when `TIDB_SMJ Hint` exists in the SQL statement in some cases [#8729](https://github.com/pingcap/tidb/pull/8729)
+- Fix the issue that `AntiSemiJoin` returns an incorrect result in some cases [#8730](https://github.com/pingcap/tidb/pull/8730)
+- Improve the valid character check of the `utf8` character set [#8754](https://github.com/pingcap/tidb/pull/8754)
+- Fix the issue that the field of the time type might return an incorrect result when the write operation is performed before the read operation in a transaction [#8746](https://github.com/pingcap/tidb/pull/8746)
+
+## PD
+
+- Fix the Region information update issue about Region merge
+[#1377](https://github.com/pingcap/pd/pull/1377)
+
+## TiKV
+
+- Support the configuration format in the unit of `DAY` (`d`) and fix the configuration compatibility issue [#3931](https://github.com/tikv/tikv/pull/3931)
+- Fix the possible panic issue caused by `Approximate Size Split` [#3942](https://github.com/tikv/tikv/pull/3942)
+- Fix two issues about Region merge [#3822](https://github.com/tikv/tikv/pull/3822), [#3873](https://github.com/tikv/tikv/pull/3873)
+
+## Tools
+
++ TiDB-Lightning
+    - Make TiDB 2.1.0 the minimum cluster version supported by Lightning
+    - Fix the content error of the file involving parsed `JSON` data in Lightning [#144](https://github.com/pingcap/tidb-tools/issues/144)
+    - Fix the issue that `Too many open engines` occurs after the checkpoint is used to restart Lightning
++ TiDB-Binlog
+    - Eliminate some bottlenecks of Drainer writing data to Kafka
+    - Support the [Kafka version of TiDB-Binlog](https://github.com/pingcap/docs-cn/blob/master/tools/tidb-binlog-kafka.md)

releases/rn.md

@@ -5,6 +5,7 @@ category: release
 
 # TiDB Release Notes
 
+- [2.1.2](../releases/2.1.2.md)
 - [2.0.10](../releases/2.0.10.md)
 - [2.1.1](../releases/2.1.1.md)
 - [2.1 GA](../releases/2.1ga.md)