TiDB 3.0.0 Beta.1 Release Notes

Release Date: March 26, 2019

TiDB version: 3.0.0-beta.1

TiDB Ansible version: 3.0.0-beta.1

Overview

On March 26, 2019, TiDB 3.0.0 Beta.1 is released. The corresponding TiDB Ansible version is 3.0.0 Beta.1. Compared with TiDB 3.0.0 Beta, this release has greatly improved the stability, usability, features, the SQL optimizer, statistics, and the execution engine.

TiDB

SQL Optimizer
- Support calculating the Cartesian product by using Sort Merge Join #9032
- Support Skyline Pruning, with some rules to prevent the execution plan from relying too heavily on statistics #9337
- Support Window Functions
  - NTILE #9682
  - LEAD and LAG #9672
  - PERCENT_RANK #9671
  - NTH_VALUE #9596
  - CUME_DIST #9619
  - FIRST_VALUE and LAST_VALUE #9560
  - RANK and DENSE_RANK #9500
  - RANGE FRAMED #9450
  - ROW FRAMED #9358
  - ROW NUMBER #9098
- Add a type of statistic that indicates the order correlation between columns and the handle column #9315
SQL Execution Engine
- Add built-in functions
  - JSON_QUOTE #7832
  - JSON_ARRAY_APPEND #9609
  - JSON_MERGE_PRESERVE #8931
  - BENCHMARK #9252
  - COALESCE #9087
  - NAME_CONST #9261
- Optimize the Chunk size based on the query context, to reduce the execution time of SQL statements and resources consumption of the cluster #6489
Privilege management
- Support SET ROLE and CURRENT_ROLE #9581
- Support DROP ROLE #9616
- Support CREATE ROLE #9461
Server
- Add the /debug/zip HTTP interface to get information of the current TiDB instance #9651
- Support the show pump status and show drainer status SQL statements to check the Pump or Drainer status 9456
- Support modifying the Pump or Drainer status by using SQL statements #9789
- Support adding HASH fingerprints to SQL text for easy tracking of slow SQL statements #9662
- Add the log_bin system variable (“0” by default) to control the enabling state of binlog; only support checking the state currently #9343
- Support managing the sending binlog strategy by using the configuration file #9864
- Support querying the slow log by using the INFORMATION_SCHEMA.SLOW_QUERY memory table #9290
- Change the MySQL version displayed in TiDB from 5.7.10 to 5.7.25 #9553
- Unify the log format for easy collection and analysis by tools
- Add the high_error_rate_feedback_total monitoring item to record the difference between the actual data volume and the estimated data volume based on statistics #9209
- Add the QPS monitoring item in the database dimension, which can be enabled by using a configuration item #9151
DDL
- Add the ddl_error_count_limit global variable (“512” by default) to limit the number of DDL task retries (If this number exceeds the limit, the DDL task is canceled) #9295
- Support ALTER ALGORITHM INPLACE/INSTANT #8811
- Support the SHOW CREATE VIEW statement #9309
- Support the SHOW CREATE USER statement #9240

PD

Unify the log format for easy collection and analysis by tools
Simulator
- Support different heartbeat intervals in different stores #1418
- Add a case about importing data #1263
Make hotspot scheduling configurable #1412
Add the store address as the dimension monitoring item to replace the previous Store ID #1429
Optimize the GetStores overhead to speed up the Region inspection cycle #1410
Add an interface to delete the Tombstone Store #1472

TiKV

Optimize the Coprocessor calculation execution framework and implement the TableScan section, with the Single TableScan performance improved by 5% ~ 30%
- Implement the definition of the BatchRows row and the BatchColumn column #3660
- Implement VectorLike to support accessing encoded and decoded data in the same way #4242
- Define the BatchExecutor to interface and implement the way of converting requests to BatchExecutor #4243
- Implement transforming the expression tree into the RPN format #4329
- Implement the BatchTableScanExecutor vectorization operator to accelerate calculation #4351
Unify the log format for easy collection and analysis by tools
Support using the Local Reader to read in the Raw Read interface #4222
Add metrics about configuration information #4206
Add metrics about key exceeding bound #4255
Add an option to control panic or return an error when encountering the key exceeding bound error #4254
Add support for the INSERT operation, make prewrite succeed only when keys do not exist, and eliminate Batch Get #4085
Use more fair batch strategy in the Batch System #4200
Support Raw scan in tikv-ctl #3825

Tools

TiDB Binlog
- Add the Arbiter tool that supports reading binlog from Kafka and replicate the data into MySQL
- Support filtering files that do not need to be replicated
- Support replicating generated columns
Lightning
- Support disabling TiKV periodic Level-1 compaction, and when the TiKV cluster version is 2.1.4 or later, Level-1 compaction is automatically executed in the import mode #119, #4199
- Add the table_concurrency configuration item to limit the number of import engines (“16” by default) and avoid overusing the importer disk space #119
- Support saving the intermediate state SST to the disk, to reduce memory usage #4369
- Optimize the import performance of TiKV-Importer and support separate import of data and indexes for large tables #132
- Support importing CSV files #111
Data replication comparison tool (sync-diff-inspector)
- Support using TiDB statistics to split chunks to be compared #197
- Support using multiple columns to split chunks to be compared #197