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