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TiDB 2.0 RC3 Release Notes

On March 23, 2018, TiDB 2.0 RC3 is released. This release has great improvement in MySQL compatibility, SQL optimization and stability.


  • Fix the wrong result issue of MAX/MIN in some scenarios
  • Fix the issue that the result of Sort Merge Join does not show in order of Join Key in some scenarios
  • Fix the error of comparison between uint and int in boundary conditions
  • Optimize checks on length and precision of the floating point type, to improve compatibility with MySQL
  • Improve the parsing error log of time type and add more error information
  • Improve memory control and add statistics about IndexLookupExecutor memory
  • Optimize the execution speed of ADD INDEX to greatly increase the speed in some scenarios
  • Use the Stream Aggregation operator when the GROUP BY substatement is empty, to increase the speed
  • Support closing the Join Reorder optimization in the optimizer using STRAIGHT_JOIN
  • Output more detailed status information of DDL jobs in ADMIN SHOW DDL JOBS
  • Support querying the original statements of currently running DDL jobs using ADMIN SHOW DDL JOB QUERIES
  • Support recovering the index data using ADMIN RECOVER INDEX for disaster recovery
  • Attach a lower priority to the ADD INDEX operation to reduce the impact on online business
  • Support aggregation functions with JSON type parameters, such as SUM/AVG
  • Support modifying the lower_case_table_names system variable in the configuration file, to support the OGG data replication tool
  • Improve compatibility with the Navicat management tool
  • Support using implicit RowID in CRUD operations


  • Support Region Merge, to merge empty Regions or small Regions after deleting data
  • Ignore the nodes that have a lot of pending peers during adding replicas, to improve the speed of restoring replicas or making nodes offline
  • Fix the frequent scheduling issue caused by a large number of empty Regions
  • Optimize the scheduling speed of leader balance in scenarios of unbalanced resources within different labels
  • Add more statistics about abnormal Regions


  • Support Region Merge
  • Inform PD immediately once the Raft snapshot process is completed, to speed up balancing
  • Add the Raw DeleteRange API
  • Add the GetMetric API
  • Reduce the I/O fluctuation caused by RocksDB sync files
  • Optimize the space reclaiming mechanism after deleting data
  • Improve the data recovery tool tikv-ctl
  • Fix the issue that it is slow to make nodes down caused by snapshot
  • Support streaming in Coprocessor
  • Support Readpool and increase the raw_get/get/batch_get by 30%
  • Support configuring the request timeout of Coprocessor
  • Support streaming aggregation in Coprocessor
  • Carry time information in Region heartbeats
  • Limit the space usage of snapshot files to avoid consuming too much disk space
  • Record and report the Regions that cannot elect a leader for a long time
  • Speed up garbage cleaning when starting the server
  • Update the size information about the corresponding Region according to compaction events
  • Limit the size of scan lock to avoid request timeout
  • Use DeleteRange to speed up Region deletion
  • Support modifying RocksDB parameters online

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