tidb-server v2.1.0-beta

• SQL Optimizer
  • Optimize the selection range of Index Join to improve the execution performance
  • Optimize correlated subquery, push down Filter, and extend the index range, to improve the efficiency of some queries by orders of magnitude
  • Support Index Hint and Join Hint in the UPDATE and DELETE statements
  • Validate Hint TIDM_SMJ when no available index exists
  • Support pushdown of the ABS, CEIL, FLOOR, IS TRUE, and IS FALSE functions
  • Handle the IF and IFNULL functions especially in the constant folding process
• SQL Execution Engine
  • Implement parallel Hash Aggregate operators and improve the computing performance of Hash Aggregate by 350% in some scenarios
  • Implement parallel Project operators and improve the performance by 74% in some scenarios
  • Read the data of the Inner table and Outer table of Hash Join concurrently to improve the execution performance
  • Fix incorrect results of INSERT … ON DUPLICATE KEY UPDATE … in some scenarios
  • Fix incorrect results of the CONCAT_WS, FLOOR, CEIL, and DIV built-in functions
• Server
  • Add the HTTP API to scatter the distribution of table Regions in the TiKV cluster
  • Add the auto_analyze_ratio system variable to control the threshold value of automatic Analyze
  • Add the HTTP API to control whether to open the general log
  • Add the HTTP API to modify the log level online
  • Add the user information in the general log and the slow query log
  • Support the server side cursor
• Compatibility
  • Support more MySQL syntax
  • Make the bit aggregate function support the ALL parameter
  • Support the SHOW PRIVILEGES statement
• DML
  • Decrease the memory usage of the INSERT INTO SELECT statement
  • Fix the performance issue of PlanCache
  • Add the tidb_retry_limit system variable to control the automatic retry times of transactions
  • Add the tidb_disable_txn_auto_retry system variable to control whether the transaction tries automatically
  • Fix the accuracy issue of the written data of the time type
  • Support the queue of locally conflicted transactions to optimize the conflicted transaction performance
  • Fix Affected Rows of the UPDATE statement
  • Optimize the statement performance of insert ignore on duplicate key update
• DDL
  • Optimize the execution speed of the CreateTable statement
  • Optimize the execution speed of ADD INDEX and improve it greatly in some scenarios
  • Fix the issue that the number of added columns by Alter table add column exceeds the limit of the number of table columns
  • Fix the issue that DDL job retries lead to an increasing pressure on TiKV in abnormal conditions
  • Fix the issue that TiDB continuously reloads the schema information in abnormal conditions
  • Do not output the FOREIGN KEY related information in the result of SHOW CREATE TABLE
  • Support the select tidb_is_ddl_owner() statement to facilitate judging whether TiDB is DDL Owner
  • Fix the issue that the index is deleted in the Year type in some scenarios
  • Fix the renaming table issue in the concurrent execution scenario
  • Support the AlterTableForce syntax
  • Support the AlterTableRenameIndex syntax with FromKey and ToKey
  • Add the table name and database name in the output information of admin show ddl jobs