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.

TiDB

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