TiDB 4.0.0 Beta.1 Release Notes

Release date: February 28, 2020

TiDB version: 4.0.0-beta.1

TiDB Ansible version: 4.0.0-beta.1

Compatibility Changes

• TiDB

  • Modify the type of the log.enable-slow-log configuration item from integer to Boolean #14864
  • Modify the password field name to authentication_string in the mysql.user system table to make it consistent with MySQL 5.7 (This compatibility change means that you cannot roll back to earlier versions.) #14598
  • Adjust the default value of the txn-total-size-limit configuration item from 1GB to 100MB #14522
  • Support dynamically modifying or updating configuration items read from PD #14750 #14303 #14830

• TiKV

  • Add the readpool.unify-read-pool configuration item (True by default) to control whether point queries use the same threads with Coprocessor #6375 #6401 #6534 #6582 #6585 #6593 #6597 #6677

• PD

  • Optimize the HTTP API to make it compatible with the configuration manager #2080

• TiDB Lightning

  • Use the default configurations specified in the document for certain items not configured in the configuration file #255

• TiDB Ansible

  • Rename theflash to tiflash #1130
  • Optimize the default values and related configurations in TiFlash's configuration file #1138

New Features

• TiDB

  • Support querying slow logs of any time in the SLOW_QUERY / CLUSTER_SLOW_QUERY system table #14840 #14878
  • Support SQL performance diagnosis
    • #14843 #14810 #14835 #14801 #14743
    • #14718 #14721 #14670 #14663 #14668
    • #14896
  • Support the Sequence function #14731 #14589 #14674 #14442 #14303 #14830
  • Support dynamically modifying or updating configuration items read from PD #14750 #14303 #14830
  • Add a feature of automatically reading data from different roles according to the load balancing policy and add the leader-and-follower system variable to enable this feature #14761
  • Add the Coercibility function #14739
  • Support setting TiFlash replicas in the partitioned table #14735 #14713 #14644
  • Improve the privilege check for the SLOW_QUERY table #14451
  • Support automatically write the intermediate results to the disk file if the memory is insufficient when using a SQL join #14708 #14279
  • Support checking table partitions by querying the information_schema.PARTITIONS system table #14347
  • Add the json_objectagg aggregate function #11154
  • Support logging rejected connection attempts in the audit log #14594
  • Add the max-server-connections configuration item (4096 by default) to control the number of connections to a single server #14409
  • Support the isolation read specifying multiple storage engines at the server level #14440
  • Optimize the cost model of the Apply operator and the Sort operator to improve stability #13550 #14708

• TiKV

  • Support fetching configuration items from the status port via HTTP API #6480
  • Optimize the performance of Chunk Encoder in Coprocessor #6341

• PD

  • Support accessing to the distribution of hotspots in the cluster through Dashboard UI #2086
  • Support capturing and displaying START_TIME and UPTIME of cluster components #2116
  • Add the information of deployment path and component version in the returned message of the member API #2130
  • Add the component sub-command in pd-ctl to modify and check the configuration of other components (experimental) #2092

• TiDB Binlog

  • Support TLS between the components #904 #894
  • Add the kafka-client-id configuration item in Drainer to configure Kafka's client ID #902
  • Support purging the incremental backup data in Drainer #885

• TiDB Ansible

  • Support deploying multiple Grafana/Prometheus/Alertmanagers in one cluster #1142
  • Add the metric_port configuration item (8234 by default) in TiFlash's configuration file #1145
  • Add the flash_proxy_status_port configuration item (20292 by default) in TiFlash's configuration file #1141
  • Add the TiFlash monitoring dashboard #1147 #1151

Bug Fixes

• TiDB

  • Fix the issue that an error is reported when creating view with a column name that exceeds 64 characters #14850
  • Fix the issue that duplicate data exists in information_schema.views because the create or replace view statement is incorrectly processed #14832
  • Fix the incorrect results of BatchPointGet when plan cache is enabled #14855
  • Fix the issue that data is inserted into the wrong partitioned table after the timezone is modified #14370
  • Fix the panic occurred when rebuilding expression using the invalid name of the IsTrue function during the outer join simplification #14515
  • Fix the the incorrect privilege check for theshow binding statement #14443

• TiKV

  • Fix the inconsistent behaviors of the CAST function in TiDB and TiKV #6463 #6461 #6459 #6474 #6492 #6569

• TiDB Lightning

  • Fix the bug that the web interface does not work outside the Server mode #259