releases, readme: add the release notes for 2.0.3 (#481)

README.md

@@ -125,6 +125,7 @@
 - [Frequently Asked Questions (FAQ)](FAQ.md)
 - [TiDB Best Practices](https://pingcap.github.io/blog/2017/07/24/tidbbestpractice/)
 + [Releases](releases/rn.md)
+  - [2.0.3](releases/203.md)
   - [2.0.2](releases/202.md)
   - [2.0.1](releases/201.md)
   - [2.0](releases/2.0ga.md)

releases/203.md

@@ -0,0 +1,37 @@
+---
+title: TiDB 2.0.3 Release Notes
+category: Releases
+---
+
+# TiDB 2.0.3 Release Notes
+
+On June 1, 2018, TiDB 2.0.3 is released. Compared with TiDB 2.0.2, this release has great improvement in system compatibility and stability.
+
+## TiDB
+
+- Support modifying the log level online
+- Support the `COM_CHANGE_USER` command
+- Support using the `TIME` type parameters under the binary protocol
+- Optimize the cost estimation of query conditions with the `BETWEEN` expression
+- Do not display the `FOREIGN KEY` information in the result of `SHOW CREATE TABLE`
+- Optimize the cost estimation for queries with the `LIMIT` clause
+- Fix the issue about the `YEAR` type as the unique index
+- Fix the issue about `ON DUPLICATE KEY UPDATE` in conditions without the unique index
+- Fix the compatibility issue of the `CEIL` function
+- Fix the accuracy issue of the `DIV` calculation in the `DECIMAL` type
+- Fix the false alarm of `ADMIN CHECK TABLE`
+- Fix the panic issue of `MAX`/`MIN` under specific expression parameters
+- Fix the issue that the result of `JOIN` is null in special conditions
+- Fix the `IN` expression issue when building and querying Range
+- Fix a Range calculation issue when using `Prepare` to query and `Plan Cache` is enabled
+- Fix the issue that the Schema information is frequently loaded in abnormal conditions
+
+## PD
+
+- Fix the panic issue when collecting hot-cache metrics in specific conditions
+- Fix the issue about scheduling of the obsolete Regions
+
+## TiKV
+
+- Fix the bug that the learner flag mistakenly reports to PD
+- Report an error instead of getting a result if `divisor/dividend` is 0 in `do_div_mod`

releases/rn.md

@@ -5,6 +5,7 @@ category: release
 
 # TiDB Release Notes
 
+  - [2.0.3](203.md)
   - [2.0.2](202.md)
   - [2.0.1](201.md)
   - [2.0](2.0ga.md)