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releases, readme: add the release notes for 2.1 beta (#516)
* releases, readme: add the release notes for 2.1 beta * Fix the format
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,85 @@ | ||
| --- | ||
| title: TiDB 2.1 Beta Release Notes | ||
| category: Releases | ||
| --- | ||
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| # TiDB 2.1 Beta Release Notes | ||
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| On June 29, 2018, TiDB 2.1 Beta is released! Compared with TiDB 2.0, this release has great improvement in stability, SQL optimizer, statistics information, and execution engine. | ||
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| ## TiDB | ||
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| - SQL Optimizer | ||
| - Optimize the selection range of `Index Join` to improve the execution performance | ||
| - Optimize correlated subquery, push down `Filter`, and extend the index range, to improve the efficiency of some queries by orders of magnitude | ||
| - Support `Index Hint` and `Join Hint` in the `UPDATE` and `DELETE` statements | ||
| - Validate Hint `TIDM_SMJ` when no available index exists | ||
| - Support pushdown of the `ABS`, `CEIL`, `FLOOR`, `IS TRUE`, and `IS FALSE` functions | ||
| - Handle the `IF` and `IFNULL` functions especially in the constant folding process | ||
| - SQL Execution Engine | ||
| - Implement parallel `Hash Aggregate` operators and improve the computing performance of `Hash Aggregate` by 350% in some scenarios | ||
| - Implement parallel `Project` operators and improve the performance by 74% in some scenarios | ||
| - Read the data of the `Inner` table and `Outer` table of `Hash Join` concurrently to improve the execution performance | ||
| - Fix incorrect results of `INSERT … ON DUPLICATE KEY UPDATE …` in some scenarios | ||
| - Fix incorrect results of the `CONCAT_WS`, `FLOOR`, `CEIL`, and `DIV` built-in functions | ||
| - Server | ||
| - Add the HTTP API to scatter the distribution of table Regions in the TiKV cluster | ||
| - Add the `auto_analyze_ratio` system variable to control the threshold value of automatic `Analyze` | ||
| - Add the HTTP API to control whether to open the general log | ||
| - Add the HTTP API to modify the log level online | ||
| - Add the user information in the general log and the slow query log | ||
| - Support the server side cursor | ||
| - Compatibility | ||
| - Support more MySQL syntax | ||
| - Make the `bit` aggregate function support the `ALL` parameter | ||
| - Support the `SHOW PRIVILEGES` statement | ||
| - DML | ||
| - Decrease the memory usage of the `INSERT INTO SELECT` statement | ||
| - Fix the performance issue of `PlanCache` | ||
| - Add the `tidb_retry_limit` system variable to control the automatic retry times of transactions | ||
| - Add the `tidb_disable_txn_auto_retry` system variable to control whether the transaction tries automatically | ||
| - Fix the accuracy issue of the written data of the `time` type | ||
| - Support the queue of locally conflicted transactions to optimize the conflicted transaction performance | ||
| - Fix `Affected Rows` of the `UPDATE` statement | ||
| - Optimize the statement performance of `insert ignore on duplicate key update` | ||
| - DDL | ||
| - Optimize the execution speed of the `CreateTable` statement | ||
| - Optimize the execution speed of `ADD INDEX` and improve it greatly in some scenarios | ||
| - Fix the issue that the number of added columns by `Alter table add column` exceeds the limit of the number of table columns | ||
| - Fix the issue that DDL job retries lead to an increasing pressure on TiKV in abnormal conditions | ||
| - Fix the issue that TiDB continuously reloads the schema information in abnormal conditions | ||
| - Do not output the `FOREIGN KEY` related information in the result of `SHOW CREATE TABLE` | ||
| - Support the `select tidb_is_ddl_owner()` statement to facilitate judging whether TiDB is `DDL Owner` | ||
| - Fix the issue that the index is deleted in the `Year` type in some scenarios | ||
| - Fix the renaming table issue in the concurrent execution scenario | ||
| - Support the `AlterTableForce` syntax | ||
| - Support the `AlterTableRenameIndex` syntax with `FromKey` and `ToKey` | ||
| - Add the table name and database name in the output information of `admin show ddl jobs` | ||
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| ## PD | ||
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| - Enable Raft PreVote between PD nodes to avoid leader reelection when network recovers after network isolation | ||
| - Optimize the issue that Balance Scheduler schedules small Regions frequently | ||
| - Optimize the hotspot scheduler to improve its adaptability in traffic statistics information jitters | ||
| - Skip the Regions with a large number of rows when scheduling `region merge` | ||
| - Enable `raft learner` by default to lower the risk of unavailable data caused by machine failure during scheduling | ||
| - Remove `max-replica` from `pd-recover` | ||
| - Add `Filter` metrics | ||
| - Fix the issue that Region information is not updated after tikv-ctl unsafe recovery | ||
| - Fix the issue that TiKV disk space is used up caused by replica migration in some scenarios | ||
| - Compatibility notes | ||
| - Do not support rolling back to v2.0.x or earlier due to update of the new version storage engine | ||
| - Enable `raft learner` by default in the new version of PD. If the cluster is upgraded from 1.x to 2.1, the machine should be stopped before upgrade or a rolling update should be first applied to TiKV and then PD | ||
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| ## TiKV | ||
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| - Upgrade Rust to the `nightly-2018-06-14` version | ||
| - Enable `Raft PreVote` to avoid leader reelection generated when network recovers after network isolation | ||
| - Add a metric to display the number of files and `ingest` related information in each layer of RocksDB | ||
| - Print `key` with too many versions when GC works | ||
| - Use `static metric` to optimize multi-label metric performance (YCSB `raw get` is improved by 3%) | ||
| - Remove `box` in multiple modules and use patterns to improve the operating performance (YCSB `raw get` is improved by 3%) | ||
| - Use `asynchronous log` to improve the performance of writing logs | ||
| - Add a metric to collect the thread status | ||
| - Decease memory copy times by decreasing `box` used in the application to improve the performance |
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