releases, readme: add 2.1 RC2 release notes (#621)

Author: lilin90

README.md

@@ -135,8 +135,9 @@
 - [Frequently Asked Questions (FAQ)](FAQ.md)
 - [TiDB Best Practices](https://pingcap.github.io/blog/2017/07/24/tidbbestpractice/)
 + [Releases](releases/rn.md)
+  - [2.1 RC2](releases/21rc2.md)
   - [2.0.7](releases/207.md)
-  - [2.1 RC1](releases/21rc1.md) 
+  - [2.1 RC1](releases/21rc1.md)
   - [2.0.6](releases/206.md)
   - [2.0.5](releases/205.md)
   - [2.1 Beta](releases/21beta.md)

releases/21rc2.md

@@ -0,0 +1,119 @@
+---
+title: TiDB 2.1 RC2 Release Notes
+category: Releases
+---
+
+# TiDB 2.1 RC2 Release Notes
+
+On September 14, 2018, TiDB 2.1 RC2 is released. Compared with TiDB 2.1 RC1, this release has great improvement in stability, SQL optimizer, statistics information, and execution engine.
+
+## TiDB
+
+* SQL Optimizer
+    * Put forward a proposal of the next generation Planner [#7543](https://github.com/pingcap/tidb/pull/7543)
+    * Improve the optimization rules of constant propagation [#7276](https://github.com/pingcap/tidb/pull/7276)
+    * Enhance the computing logic of `Range` to enable it to handle multiple `IN` or `EQUAL` conditions simultaneously [#7577](https://github.com/pingcap/tidb/pull/7577)
+    * Fix the issue that the estimation result of `TableScan` is incorrect when `Range` is empty [#7583](https://github.com/pingcap/tidb/pull/7583)
+    * Support the `PointGet` operator for the `UPDATE` statement [#7586](https://github.com/pingcap/tidb/pull/7586)
+    * Fix the panic issue during the process of executing the `FirstRow` aggregate function in some conditions [#7624](https://github.com/pingcap/tidb/pull/7624)
+* SQL Execution Engine
+    * Fix the potential `DataRace` issue when the `HashJoin` operator encounters an error [#7554](https://github.com/pingcap/tidb/pull/7554)
+    * Make the `HashJoin` operator read the inner table and build the hash table simultaneously [#7544](https://github.com/pingcap/tidb/pull/7544)
+    * Optimize the performance of Hash aggregate operators [#7541](https://github.com/pingcap/tidb/pull/7541)
+    * Optimize the performance of Join operators [#7493](https://github.com/pingcap/tidb/pull/7493), [#7433](https://github.com/pingcap/tidb/pull/7433)
+    * Fix the issue that the result of `UPDATE JOIN` is incorrect when the Join order is changed [#7571](https://github.com/pingcap/tidb/pull/7571)
+    * Improve the performance of Chunk’s iterator [#7585](https://github.com/pingcap/tidb/pull/7585)
+* Statistics
+    * Fix the issue that the auto Analyze work repeatedly analyzes the statistics [#7550](https://github.com/pingcap/tidb/pull/7550)
+    * Fix the statistics update error that occurs when there is no statistics change [#7530](https://github.com/pingcap/tidb/pull/7530)
+    * Use the RC isolation level and low priority when building `Analyze` requests [#7496](https://github.com/pingcap/tidb/pull/7496)
+    * Support enabling statistics auto-analyze on certain period of a day [#7570](https://github.com/pingcap/tidb/pull/7570)
+    * Fix the panic issue when logging the statistics information [#7588](https://github.com/pingcap/tidb/pull/7588)
+    * Support configuring the number of buckets in the histogram using the `ANALYZE TABLE WITH BUCKETS` statement [#7619](https://github.com/pingcap/tidb/pull/7619)
+    * Fix the panic issue when updating an empty histogram [#7640](https://github.com/pingcap/tidb/pull/7640)
+    * Update `information_schema.tables.data_length` using the statistics information [#7657](https://github.com/pingcap/tidb/pull/7657)
+* Server
+    * Add Trace related dependencies [#7532](https://github.com/pingcap/tidb/pull/7532)
+    * Enable the `mutex profile` feature of Golang  [#7512](https://github.com/pingcap/tidb/pull/7512)
+    * The `Admin` statement requires the `Super_priv` privilege [#7486](https://github.com/pingcap/tidb/pull/7486)
+    * Forbid users to `Drop` crucial system tables [#7471](https://github.com/pingcap/tidb/pull/7471)
+    * Switch from `juju/errors` to `pkg/errors` [#7151](https://github.com/pingcap/tidb/pull/7151)
+    * Complete the functional prototype of SQL Tracing [#7016](https://github.com/pingcap/tidb/pull/7016)
+    * Remove the goroutine pool [#7564](https://github.com/pingcap/tidb/pull/7564)
+    * Support viewing the goroutine information using the `USER1` signal [#7587](https://github.com/pingcap/tidb/pull/7587)
+    * Set the internal SQL to high priority while TiDB is started [#7616](https://github.com/pingcap/tidb/pull/7616)
+    * Use different labels to filter internal SQL and user SQL in monitoring metrics [#7631](https://github.com/pingcap/tidb/pull/7631)
+    * Store the top 30 slow queries in the last week to the TiDB server [#7646](https://github.com/pingcap/tidb/pull/7646)
+    * Put forward a proposal of setting the global system time zone for the TiDB cluster [#7656](https://github.com/pingcap/tidb/pull/7656)
+    * Enrich the error message of “GC life time is shorter than transaction duration” [#7658](https://github.com/pingcap/tidb/pull/7658)
+    * Set the global system time zone when starting the TiDB cluster [#7638](https://github.com/pingcap/tidb/pull/7638)
+* Compatibility
+    * Add the unsigned flag for the `Year` type [#7542](https://github.com/pingcap/tidb/pull/7542)
+    * Fix the issue of configuring the result length of the `Year` type in the `Prepare`/`Execute` mode [#7525](https://github.com/pingcap/tidb/pull/7525)
+    * Fix the issue of inserting zero timestamp in the `Prepare`/`Execute` mode [#7506](https://github.com/pingcap/tidb/pull/7506)
+    * Fix the error handling issue of the integer division [#7492](https://github.com/pingcap/tidb/pull/7492)
+    * Fix the compatibility issue when processing `ComStmtSendLongData` [#7485](https://github.com/pingcap/tidb/pull/7485)
+    * Fix the error handling issue during the process of converting string to integer [#7483](https://github.com/pingcap/tidb/pull/7483)
+    * Optimize the accuracy of values in the `information_schema.columns_in_table` table [#7463](https://github.com/pingcap/tidb/pull/7463)
+    * Fix the compatibility issue when writing or updating the string type of data using the MariaDB client [#7573](https://github.com/pingcap/tidb/pull/7573)
+    * Fix the compatibility issue of aliases of the returned value [#7600](https://github.com/pingcap/tidb/pull/7600)
+    * Fix the issue that the `NUMERIC_SCALE` value of the float type is incorrect in the `information_schema.COLUMNS` table [#7602](https://github.com/pingcap/tidb/pull/7602)
+    * Fix the issue that Parser reports an error when the single line comment is empty [#7612](https://github.com/pingcap/tidb/pull/7612)
+* Expressions
+    * Check the value of `max_allowed_packet` in the `insert` function [#7528](https://github.com/pingcap/tidb/pull/7528)
+    * Support the built-in function `json_contains`  [#7443](https://github.com/pingcap/tidb/pull/7443)
+    * Support the built-in function `json_contains_path` [#7596](https://github.com/pingcap/tidb/pull/7596)
+    * Support the built-in function `encode/decode` [#7622](https://github.com/pingcap/tidb/pull/7622)
+    * Fix the issue that some time related functions are not compatible with the MySQL behaviors in some cases [#7636](https://github.com/pingcap/tidb/pull/7636)
+    * Fix the compatibility issue of parsing the time type of data in string [#7654](https://github.com/pingcap/tidb/pull/7654)
+    * Fix the issue that the time zone is not considered when computing the default value of the `DateTime` data [#7655](https://github.com/pingcap/tidb/pull/7655)
+* DML
+    * Set correct `last_insert_id` in the `InsertOnDuplicateUpdate` statement [#7534](https://github.com/pingcap/tidb/pull/7534)
+    * Reduce the cases of updating the `auto_increment_id` counter [#7515](https://github.com/pingcap/tidb/pull/7515)
+    * Optimize the error message of `Duplicate Key` [#7495](https://github.com/pingcap/tidb/pull/7495)
+    * Fix the `insert...select...on duplicate key update` issue [#7406](https://github.com/pingcap/tidb/pull/7406)
+    * Support the `LOAD DATA IGNORE LINES` statement [#7576](https://github.com/pingcap/tidb/pull/7576)
+* DDL
+    * Add the DDL job type and the current schema version information in the monitor [#7472](https://github.com/pingcap/tidb/pull/7472)
+    * Complete the design of the `Admin Restore Table` feature [#7383](https://github.com/pingcap/tidb/pull/7383)
+    * Fix the issue that the default value of the `Bit` type exceeds 128 [#7249](https://github.com/pingcap/tidb/pull/7249)
+    * Fix the issue that the default value of the `Bit` type cannot be `NULL` [#7604](https://github.com/pingcap/tidb/pull/7604)
+    * Reduce the interval of checking `CREATE TABLE/DATABASE` in the DDL queue [#7608](https://github.com/pingcap/tidb/pull/7608)
+    * Use the `ddl/owner/resign` HTTP interface ro release the DDL owner and start electing a new owner [#7649](https://github.com/pingcap/tidb/pull/7649)
+* TiKV Go Client
+    * Support the issue that the `Seek` operation only obtains `Key` [#7419](https://github.com/pingcap/tidb/pull/7419)
+* [Table Partition](https://github.com/pingcap/tidb/projects/6) (Experimental)
+    * Fix the issue that the `Bigint` type cannot be used as the partition key  [#7520](https://github.com/pingcap/tidb/pull/7520)
+    * Support the rollback operation when an issue occurs during adding an index in the partitioned table [#7437](https://github.com/pingcap/tidb/pull/7437)
+
+## PD
+
+* Features
+    * Support the `GetAllStores` interface [#1228](https://github.com/pingcap/pd/pull/1228)
+    * Add the statistics of scheduling estimation in Simulator [#1218](https://github.com/pingcap/pd/pull/1218)
+* Improvements
+    * Optimize the handling process of down stores to make up replicas as soon as possible [#1222](https://github.com/pingcap/pd/pull/1222)
+    * Optimize the start of Coordinator to reduce the unnecessary scheduling caused by restarting PD [#1225](https://github.com/pingcap/pd/pull/1225)
+    * Optimize the memory usage to reduce the overhead caused by heartbeats [#1195](https://github.com/pingcap/pd/pull/1195)
+    * Optimize error handling and improve the log information [#1227](https://github.com/pingcap/pd/pull/1227)
+    * Support querying the Region information of a specific store in pd-ctl [#1231](https://github.com/pingcap/pd/pull/1231)
+    * Support querying the topN Region information based on version comparasion in pd-ctl [#1233](https://github.com/pingcap/pd/pull/1233)
+    * Support more accurate TSO decoding in pd-ctl [#1242](https://github.com/pingcap/pd/pull/1242)
+* Bug fix
+    * Fix the issue that pd-ctl uses the `hot store` command to exit wrongly [#1244](https://github.com/pingcap/pd/pull/1244)
+
+## TiKV
+
+* Performance
+    * Support splitting Regions based on statistics estimation to reduce the I/O cost [#3511](https://github.com/tikv/tikv/pull/3511)
+    * Reduce clone in the transaction scheduler [#3530](https://github.com/tikv/tikv/pull/3530)
+* Improvements
+    * Add the pushdown support for a large number of built-in functions
+    * Add the `leader-transfer-max-log-lag` configuration to fix the failure issue of leader scheduling in specific scenarios [#3507](https://github.com/tikv/tikv/pull/3507)
+    * Add the `max-open-engines` configuration to limit the number of engines opened by `tikv-importer` simultaneously [#3496](https://github.com/tikv/tikv/pull/3496)
+    * Limit the cleanup speed of garbage data to reduce the impact on `snapshot apply` [#3547](https://github.com/tikv/tikv/pull/3547)
+    * Broadcast the commit message for crucial Raft messages to avoid unnecessary delay [#3592](https://github.com/tikv/tikv/pull/3592)
+* Bug fixes
+    * Fix the leader election issue caused by discarding the `PreVote` message of the newly split Region [#3557](https://github.com/tikv/tikv/pull/3557)
+    * Fix follower related statistics after merging Regions [#3573](https://github.com/tikv/tikv/pull/3573)
+    * Fix the issue that the local reader uses obsolete Region information [#3565](https://github.com/tikv/tikv/pull/3565)

releases/rn.md

@@ -5,6 +5,7 @@ category: release
 
 # TiDB Release Notes
 
+  - [2.1 RC2](21rc2.md)
   - [2.0.7](207.md)
   - [2.1 RC1](21rc1.md)
   - [2.0.6](206.md)