TiDB 2.0 RC1 Release Notes

On March 9, 2018, TiDB 2.0 RC1 is released. This release has great improvement in MySQL compatibility, SQL optimization and stability.

TiDB

Support limiting the memory usage by a single SQL statement, to reduce the risk of OOM
Support pushing the Stream Aggregate operator down to TiKV
Support validating the configuration file
Support obtaining the information of TiDB configuration through HTTP API
Compatible with more MySQL syntax in Parser
Improve the compatibility with Navicat
Improve the optimizer and extract common expressions with multiple OR conditions, to choose better query plan
Improve the optimizer and convert subqueries to Join operators in more scenarios, to choose better query plan
Resolve Lock in the Batch mode to increase the garbage collection speed
Fix the length of Boolean field to improve compatibility
Optimize the Add Index operation and give lower priority to all write and read operations, to reduce the impact on online business

Optimize the logic of code used to check the Region status to improve performance
Optimize the output of log information in abnormal conditions to facilitate debugging
Fix the monitor statistics that the disk space of TiKV nodes is not enough
Fix the wrong reporting issue of the health interface when TLS is enabled
Fix the issue that concurrent addition of replicas might exceed the threshold value of configuration, to improve stability

Fix the issue that gRPC call is not cancelled when PD leaders switch
Protect important configuration which cannot be changed after initial configuration
Add gRPC APIs used to obtain metrics
Check whether SSD is used when you start the cluster
Optimize the read performance using ReadPool, and improve the performance by 30% in the raw get test
Improve metrics and optimize the usage of metrics