tidb-server v2.0.0

• SQL Optimizer
  • Use more compact data structure to reduce the memory usage of statistics information
  • Speed up the loading statistics information when starting a tidb-server process
  • Support updating statistics information dynamically [experimental]
  • Optimize the cost model to provide more accurate query cost evaluation
  • Use Count-Min Sketch to estimate the cost of point queries more accurately
  • Support analyzing more complex conditions to make full use of indexes
  • Support manually specifying the Join order using the STRAIGHT_JOIN syntax
  • Use the Stream Aggregation operator when the GROUP BY clause is empty to improve the performance
  • Support using indexes for the MAX/MIN function
  • Optimize the processing algorithms for correlated subqueries to support decorrelating more types of correlated subqueries and transform them to Left Outer Join
  • Extend IndexLookupJoin to be used in matching the index prefix
• SQL Execution Engine
  • Refactor all operators using the Chunk architecture, improve the execution performance of analytical queries, and reduce memory usage.There is a significant improvement in the TPC-H benchmark result.
  • Support the Streaming Aggregation operators pushdown
  • Optimize the Insert Into Ignore statement to improve the performance by over 10 times
  • Optimize the Insert On Duplicate Key Update statement to improve the performance by over 10 times
  • Optimize Load Data to improve the performance by over 10 times
  • Push down more data types and functions to TiKV
  • Support computing the memory usage of physical operators, and specifying the processing behavior in the configuration file and system variables when the memory usage exceeds the threshold
  • Support limiting the memory usage by a single SQL statement to reduce the risk of OOM
  • Support using implicit RowID in CRUD operations
  • Improve the performance of point queries
• Server
  • Support the Proxy Protocol
  • Add more monitoring metrics and refine the log
  • Support validating the configuration files
  • Support obtaining the information of TiDB parameters through HTTP API
  • Resolve Lock in the Batch mode to speed up garbage collection
  • Support multi-threaded garbage collection
  • Support TLS
• Compatibility
  • Support more MySQL syntaxes
  • Support modifying the lower_case_table_names system variable in the configuration file to support the OGG data synchronization tool
  • Improve compatibility with the Navicat management tool
  • Support displaying the table creating time in Information_Schema
  • Fix the issue that the return types of some functions/expressions differ from MySQL
  • Improve compatibility with JDBC
  • Support more SQL Modes
• DDL
  • Optimize the Add Index operation to greatly improve the execution speed in some scenarios
  • Attach a lower priority to the Add Index operation to reduce the impact on online business
  • Output more detailed status information of the DDL jobs in Admin Show DDL Jobs
  • Support querying the original statements of currently running DDL jobs using Admin Show DDL Job Queries JobID
  • Support recovering the index data using Admin Recover Index for disaster recovery
  • Support modifying Table Options using the Alter statement

tidb-server v1.0.9

• Fix a panic error in the Drop Column or Add Column statement
• Fix the issue that Alter Table Modify Column reports an error in extreme conditions
• Fix the issue that the NULL value is inserted while adding NOT NULL columns

tidb-server v2.0.0-rc.6

• Fix an issue about rolling update to release candidate version higher than 2.0.0-rc4

tidb-server v2.0.0-rc.5

• Fix the issue about applying the Top-N pushdown rule
• Fix the estimation of the number of rows for the columns that contain NULL values
• Fix the zero value of the Binary type
• Fix the BatchGet issue within a transaction
• Clean up the written data while rolling back the Add Index operation, to reduce consumed space
• Optimize the insert on duplicate key update statement to improve the performance by 10 times
• Fix the issue about the type of the results returned by the UNIX_TIMESTAMP function
• Fix the issue that the NULL value is inserted while adding NOT NULL columns
• Support showing memory usage of the executing statements in the Show Process List statement
• Fix the issue that Alter Table Modify Column reports an error in extreme conditions
• Support setting the table comment using the Alter statement

tidb-server v2.0.0-rc.4

• Support SHOW GRANTS FOR CURRENT_USER();
• Fix the issue that the Expression in UnionScan is not cloned
• Support the SET TRANSACTION syntax
• Fix the potential goroutine leak issue in copIterator
• Fix the issue that admin check table misjudges the unique index including null
• Support displaying floating point numbers using scientific notation
• Fix the type inference issue during binary literal computing
• Fix the issue in parsing the CREATE VIEW statement
• Fix the panic issue when one statement contains both ORDER BY and LIMIT 0
• Improve the execution performance of DecodeBytes
• Optimize LIMIT 0 to TableDual, to avoid building useless execution plans

tidb-server v2.0.0-rc.3

• 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 bypass 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 synchronization tool
• Improve compatibility with the Navicat management tool
• Support using implicit RowID in CRUD operations

tidb-server v2.0.0-rc.1

• 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 configuration of TiDB 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 a better query plan
• Improve the optimizer and convert subqueries to Join operators in more scenarios, to choose a 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

tidb-server v1.1.0-beta

• Add more monitoring metrics and refine the log
• Compatible with more MySQL syntax
• Support displaying the table creating time in information_schema
• Optimize queries containing the MaxOneRow operator
• Configure the size of intermediate result sets generated by Join, to further reduce the memory used by Join
• Add the tidb_config session variable to output the current TiDB configuration
• Fix the panic issue in the Union and Index Join operators
• Fix the wrong result issue of the Sort Merge Join operator in some scenarios
• Fix the issue that the Show Index statement shows indexes that are in the process of adding
• Fix the failure of the Drop Stats statement
• Optimize the query performance of the SQL engine to improve the test result of the Sysbench -
  Select/OLTP by 10%
• Improve the computing speed of subqueries in the optimizer using the new execution engine; compared with TiDB 1.0, TiDB 1.1 Beta has great improvement in tests like TPC-H and TPC-DS

tidb-server v1.0.8

• Fix issues in the Outer Join result in some scenarios
• Optimize the performance of the InsertIntoIgnore statement
• Fix the issue in the ShardRowID option
• Add limitation (Configurable, the default value is 5000) to the DML statements number within a transaction
• Fix an issue in the Table/Column aliases returned by the Prepare statement
• Fix an issue in updating statistics delta
• Fix a panic error in the Drop Column statement
• Fix an DML issue when running the Add Column After statement
• Improve the stability of the GC process by ignoring the regions with GC errors
• Run GC concurrently to accelerate the GC process
• Provide syntax support for the CREATE INDEX statement

tidb-server v1.1.0-alpha.1

• SQL parser
  • Support more syntax
• SQL query optimizer
  • Use more compact structure to reduce statistics info memory usage
  • Speed up loading statistics info when starting the tidb-server
  • Provide more accurate query cost evaluation
  • Use Count-Min Sketch to evaluate the cost of queries using unique index more accurately
  • Support more complex conditions to make full use of index
• SQL executor
  • Refactor all executor operators using Chunk architecture, improve the execution performance of analytical statements and reduce memory usage
  • Optimize performance of the INSERT IGNORE statement
  • Push down more types and functions to TiKV
  • Support more SQL_MODE
  • Optimize the Load Data performance to increase the speed by 10 times
  • Optimize the Use Database performance
  • Support statistics on the memory usage of physical operators
• Server
  • Support the PROXY protocol