tidb-server v2.0.10

• Fix the possible issue caused by canceling a DDL job #8513
• Fix the issue that the ORDER BY and UNION clauses cannot quote the column including a table name #8514
• Fix the issue that the UNCOMPRESS function does not judge the incorrect input length #8607
• Fix the issue encountered by ANSI_QUOTES SQL_MODE when upgrading TiDB #8575
• Fix the issue that SELECT returns the wrong result in some cases #8570
• Fix the possible issue that TiDB cannot exit when it receives the exit signal #8501
• Fix the issue that IndexLookUpJoin returns the wrong result in some cases #8508
• Avoid pushing down the filter containing GetVar or SetVar #8454
• Fix the issue that the result length of the UNION clauses is incorrect in some cases #8491
• Fix the issue of PREPARE FROM @var_name #8488
• Fix the panic issue when dumping statistics information in some cases #8464
• Fix the statistics estimation issue of point queries in some cases #8493
• Fix the panic issue when the returned default enum value is a string #8476
• Fix the issue that too much memory is consumed in the scenario of wide tables #8467
• Fix the issue encountered when Parser incorrectly formats the mod opcode #8431
• Fix the panic issue caused by adding foreign key constraints in some cases #8421 #8410
• Fix the issue that the YEAR column type incorrectly converts the zero value #8396
• Fix the panic issue occurred when the argument of the VALUES function is not a column #8404
• Disable Plan Cache for statements containing subqueries #8395

tidb-server v2.1.1

SQL Optimizer/Executor

• Fix the round error of the negative date #8574
• Fix the issue that the uncompress function does not check the data length #8606
• Reset bind arguments of the prepare statement after the execute command is executed #8652
• Support automatically collecting the statistics information of a partition table #8649
• Fix the wrongly configured integer type when pushing down the abs function #8628
• Fix the data race on the JSON column #8660

Server

• Fix the issue that the transaction obtained TSO is incorrect when PD breaks down #8567
• Fix the bootstrap failure caused by the statement that does not conform to ANSI standards #8576
• Fix the issue that incorrect parameters are used in transaction retries #8638

DDL

• Change the default character set and collation of tables into utf8mb4 #8590
• Add the ddl_reorg_batch_size variable to control the speed of adding indexes #8614
• Make the character set and collation options content in DDL case-insensitive #8611
• Fix the issue of adding indexes for generated columns #8655

tidb-server v2.1.0

Upgrade caveat

• TiDB 2.1 does not support downgrading to v2.0.x or earlier due to the adoption of the new storage engine
• Parallel DDL is enabled in TiDB 2.1, so the clusters with TiDB version earlier than 2.0.1 cannot upgrade to 2.1 using rolling update. You can choose either of the following two options:
  • Stop the cluster and upgrade to 2.1 directly
  • Roll update to 2.0.1 or later 2.0.x versions, and then roll update to the 2.1 version
• If you upgrade from TiDB 2.0.6 or earlier to TiDB 2.1, make sure if there is any ongoing DDL operation, especially the time consuming Add Index operation, because the DDL operations slow down the upgrading process.

SQL Optimizer

• Optimize the selection range of Index Join to improve the execution performance
• Optimize the selection of outer table for Index Join and use the table with smaller estimated value of Row Count as the outer table
• Optimize Join Hint TIDB_SMJ so that Merge Join can be used even without proper index available
• Optimize Join Hint TIDB_INLJ to specify the Inner table to Join
• Optimize correlated subquery, push down Filter, and extend the index selection range, to improve the efficiency of some queries by orders of magnitude
• Support using Index Hint and Join Hint in the UPDATE and DELETE statement
• Support pushing down more functions:ABS / CEIL / FLOOR / IS TRUE / IS FALSE
• Optimize the constant folding algorithm for the IF and IFNULL built-in functions
• Optimize the output of the EXPLAIN statement and use hierarchy structure to show the relationship between operators

SQL executor

• Refactor all the aggregation functions and improve execution efficiency of the Stream and Hash aggregation operators
• Implement the parallel Hash Aggregate operators and improve the computing performance by 350% in some scenarios
• Implement the 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
• Optimize the execution speed of the REPLACE INTO statement and increase the performance nearly by 10 times
• Optimize the memory usage of the time data type and decrease the memory usage of the time data type by fifty percent
• Optimize the point select performance and improve the point select efficiency result of Sysbench by 60%
• Improve the performance of TiDB on inserting or updating wide tables by 20 times
• Support configuring the memory upper limit of a single statement in the configuration file
• Optimize the execution of Hash Join, if the Join type is Inner Join or Semi Join and the inner table is empty, return the result without reading data from the outer table
• Support using the EXPLAIN ANALYZE statement to check the runtime statistics including the execution time and the number of returned rows of each operator

Statistics

• Support enabling auto ANALYZE statistics only during certain period of the day
• Support updating the table statistics automatically according to the feedback of the queries
• Support configuring the number of buckets in the histogram using the ANALYZE TABLE WITH BUCKETS statement
• Optimize the Row Count estimation algorithm using histogram for mixed queries of equality query and range queries

Expressions

• Support following built-in function:
  • json_contains
  • json_contains_path
  • encode/decode

Server

• Support queuing the locally conflicted transactions within tidb-server instance to optimize the performance of conflicted transactions
• Support Server Side Cursor
• Add the HTTP API
  • Scatter the distribution of table Regions in the TiKV cluster
  • Control whether to open the general log
  • Support modifying the log level online
  • Check the TiDB cluster information
• Add the auto_analyze_ratio system variables to contorl the ratio of Analyze
• 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 retries automatically
• Support using admin show slow statement to obtain the slow queries
• Add the tidb_slow_log_threshold environment variable to set the threshold of slow log automatically
• Add the tidb_query_log_max_len environment variable to set the length of the SQL statement to be truncated in the log dynamically

DDL

• Support the parallel execution of the add index statement and other statements to avoid the time consuming add index operation blocking other operations
• Optimize the execution speed of ADD INDEX and improve it greatly in some scenarios
• Support the select tidb_is_ddl_owner() statement to facilitate deciding whether TiDB is DDL Owner
• Support the ALTER TABLE FORCE syntax
• Support the ALTER TABLE RENAME KEY TO syntax
• Add the table name and database name in the output information of admin show ddl jobs
• Support using the ddl/owner/resign HTTP interface to release the DDL owner and start electing a new DDL owner

Compatibility

• Support more MySQL syntaxes
• Make the BIT aggregate function support the ALL parameter
• Support the SHOW PRIVILEGES statement
• Support the CHARACTER SET syntax in the LOAD DATA statement
• Support the IDENTIFIED WITH syntax in the CREATE USER statement
• Support the LOAD DATA IGNORE LINES statement
• The Show ProcessList statement returns more accurate information

tidb-server v2.0.9

• Fix the issue caused by the empty statistics histogram #7927
• Fix the panic issue of the UNION ALL statement in some cases #7942
• Fix the stack overflow issue caused by wrong DDL Jobs #7959
• Add the slow log for the Commit operation #7983
• Fix the panic issue caused by the too large Limit value #8004
• Support specifying the utf8mb4 character set in the USING clause #8048
• Make the TRUNCATE built-in function support parameters of unsigned integer type #8069
• Fix the selectivity estimation issue of the primary key for the statistics module in some cases #8150
• Add the Session variable to control whether _tidb_rowid is allowed to be written in #8126
• Fix the panic issue of PhysicalProjection in some cases #8154
• Fix the unstable results of the Union statement in some cases #8168
• Fix the issue that NULL is not returned by values in the non-Insert statement #8179
• Fix the issue that the statistics module cannot clear the outdated data in some cases #8184
• Make the maximum allowed running time for a transaction a configurable option 8209
• Fix the wrong comparison algorithm of expression rewriter in some cases #8288
• Eliminate the extra columns generated by the UNION ORDER BY statement #8307
• Support the admin show next_row_id statement #8274
• Fix the escape issue of special characters in the Show Create Table statement #8321
• Fix the unexpected errors in the UNION statement in some cases #8318
• Fix the issue that canceling a DDL job causes no rollback of a schema in some cases #8312
• Change tidb_max_chunk_size to a global variable #8333
• Add an upper bound to the Scan command of ticlient, to avoid overbound scan #8309, #8310

tidb-server v2.1.0-rc.5

SQL Optimizer

• Fix the issue that IndexReader reads the wrong handle in some cases #8132
• Fix the issue occurred while the IndexScan Prepared statement uses Plan Cache #8055
• Fix the issue that the result of the Union statement is unstable #8165

SQL Execution Engine

• Improve the performance of TiDB on inserting or updating wide tables #8024
• Support the unsigned int flag in the Truncate built-in function #8068
• Fix the error occurred while converting JSON data to the decimal type #8109
• Fix the error occurred when you Update the float type #8170

Statistics

• Fix the incorrect statistics issue during point queries in some cases #8035
• Fix the selectivity estimation of statistics for primary key in some cases #8149
• Fix the issue that the statistics of deleted tables are not cleared up for a long period of time #8182

Server

• Improve the readability of logs and make logs better
  • #8063
  • #8053
  • #8224
• Fix the error occurred when obtaining the table data of infoschema.profiling #8096
• Replace the unix socket with the pumps client to write binlogs #8098
• Add the threshold value for the tidb_slow_log_threshold environment variable, which dynamically sets the slow log #8094
• Add the original length of a SQL statement truncated while the tidb_query_log_max_len environment variable dynamically sets logs 8200
• Add the tidb_opt_write_row_id environment variable to control whether to allow writing _tidb_rowid #8218
• Add an upper bound to the Scan command of ticlient, to avoid overbound scan #8081, #8247

DDL

• Fix the issue that executing DDL statements in transactions encounters an error in some cases #8056
• Fix the issue that executing truncate table in partition tables does not take effect #8103
• Fix the issue that the DDL operation does not roll back correctly after being cancelled in some cases #8057
• Add the admin show next_row_id command to return the next available row ID #8268

tidb-server v2.1.0-rc.4

SQL Optimizer

• Fix the issue that column pruning of UnionAll is incorrect in some cases #7941
• Fix the issue that the result of the UnionAll operator is incorrect in some cases #8007

SQL Execution Engine

• Fix the precision issue of the AVG function #7874
• Support using the EXPLAIN ANALYZE statement to check the runtime statistics including the execution time and the number of returned rows of each operator during the query execution process #7925
• Fix the panic issue of the PointGet operator when a column of a table appears multiple times in the result set #7943
• Fix the panic issue caused by too large values in the Limit subclause #8002
• Fix the panic issue during the execution process of the AddDate/SubDate statement in some cases #8009

Statistics

• Fix the issue of judging the prefix of the histogram low-bound of the combined index as out of range #7856
• Fix the memory leak issue caused by statistics collecting #7873
• Fix the panic issue when the histogram is empty #7928
• Fix the issue that the histogram bound is out of range when the statistics is being uploaded #7944
• Limit the maximum length of values in the statistics sampling process #7982

Server

• Refactor Latch to avoid misjudgment of transaction conflicts and improve the execution performance of concurrent transactions #7711
• Fix the panic issue caused by collecting slow queries in some cases #7874
• Fix the panic issue when ESCAPED BY is an empty string in the LOAD DATA statement #8005
• Complete the “coprocessor error” log information #8006

Compatibility

• Set the Command field of the SHOW PROCESSLIST result to Sleep when the query is empty #7839

Expressions

• Fix the constant folding issue of the SYSDATE function #7895
• Fix the issue that SUBSTRING_INDEX panics in some cases #7897

DDL

• Fix the stack overflow issue caused by throwing the invalid ddl job type error #7958
• Fix the issue that the result of ADMIN CHECK TABLE is incorrect in some cases #7975

tidb-server v2.0.8

Improvements

• Slow down the AUTO_INCREMENT ID increasing speed when the Update statement does not modify the corresponding AUTO_INCREMENT column #7846

Bug fixes

• Quickly create a new etcd session to recover the service when the PD leader goes down #7810
• Fix the issue that the time zone is not considered when the default value of the DateTime type is calculated #7672
• Fix the issue that duplicate key update inserts values incorrectly in some conditions #7685
• Fix the issue that the predicate conditions of UnionScan are not pushed down #7726
• Fix the issue that the time zone is not correctly handled when you add the TIMESTAMP index #7812
• Fix the memory leak issue caused by the statistics module in some conditions #7864
• Fix the issue that the results of ANALYZE cannot be obtained in some abnormal conditions #7871
• Do not fold the function SYSDATE, to ensure the returned results are correct #7894
• Fix the substring_index panic issue in some conditions #7896
• Fix the issue that OUTER JOIN is mistakenly converted to INNER JOIN in some conditions #7899

tidb-server v2.1.0-rc.3

SQL Optimizer

• Fix the incorrect result issue when a statement contains embedded LEFT OUTER JOIN #7689
• Enhance the optimization rule of predicate pushdown on the JOIN statement #7645
• Fix the optimization rule of predicate pushdown for the UnionScan operator #7695
• Fix the issue that the unique key property of the Union operator is not correctly set #7680
• Enhance the optimization rule of constant folding #7696
• Optimize the data source in which the filter is null after propagation to table dual #7756

SQL Execution Engine

• Optimize the performance of read requests in a transaction #7717
• Optimize the cost of allocating Chunk memory in some executors #7540
• Fix the "index out of range" panic caused by the columns where point queries get all NULL values #7790

Server

• Fix the issue that the memory quota in the configuration file does not take effect #7729
• Add the tidb_force_priority system variable to set the execution priority for each statement #7694
• Support using the admin show slow statement to obtain the slow query log #7785

Compatibility

• Fix the issue that the result of charset/collation is incorrect in information_schema.schemata #7751
• Fix the issue that the value of the hostname system variable is empty #7750

Expressions

• Support the init_vecter argument in the AES_ENCRYPT/AES_DECRYPT built-in function #7425
• Fix the issue that the result of Format is incorrect in some expressions #7770
• Support the JSON_LENGTH built-in function #7739
• Fix the incorrect result issue when casting the unsigned integer type to the decimal type #7792

DML

• Fix the issue that the result of the INSERT … ON DUPLICATE KEY UPDATE statement is incorrect while updating the unique key #7675

DDL

• Fix the issue that the index value is not converted between time zones when you create a new index on a new column of the timestamp type #7724
• Support appending new values for the enum type #7767
• Support creating an etcd session quickly, which improves the cluster availability after network isolation #7774

tidb-server v2.1.0-rc.2

SQL Optimizer

• Put forward a proposal of the next generation Planner #7543
• Improve the optimization rules of constant propagation #7276
• Enhance the computing logic of Range to enable it to handle multiple IN or EQUAL conditions simultaneously #7577
• Fix the issue that the estimation result of TableScan is incorrect when Range is empty #7583
• Support the PointGet operator for the UPDATE statement #7586
• Fix the panic issue during the process of executing the FirstRow aggregate function in some conditions #7624

SQL Execution Engine

• Fix the potential DataRace issue when the HashJoin operator encounters an error #7554
• Make the HashJoin operator read the inner table and build the hash table simultaneously #7544
• Optimize the performance of Hash aggregate operators #7541
• Optimize the performance of Join operators #7493, #7433
• Fix the issue that the result of UPDATE JOIN is incorrect when the Join order is changed #7571
• Improve the performance of Chunk’s iterator #7585

Statistics

• Fix the issue that the auto Analyze work repeatedly analyzes the statistics #7550
• Fix the statistics update error that occurs when there is no statistics change #7530
• Use the RC isolation level and low priority when building Analyze requests #7496
• Support enabling statistics auto-analyze on certain period of a day #7570
• Fix the panic issue when logging the statistics information #7588
• Support configuring the number of buckets in the histogram using the ANALYZE TABLE WITH BUCKETS statement #7619
• Fix the panic issue when updating an empty histogram #7640
• Update information_schema.tables.data_length using the statistics information #7657

Server

• Add Trace related dependencies #7532
• Enable the mutex profile feature of Golang #7512
• The Admin statement requires the Super_priv privilege #7486
• Forbid users to Drop crucial system tables #7471
• Switch from juju/errors to pkg/errors #7151
• Complete the functional prototype of SQL Tracing #7016
• Remove the goroutine pool #7564
• Support viewing the goroutine information using the USER1 signal #7587
• Set the internal SQL to high priority while TiDB is started #7616
• Use different labels to filter internal SQL and user SQL in monitoring metrics #7631
• Store the top 30 slow queries in the last week to the TiDB server #7646
• Put forward a proposal of setting the global system time zone for the TiDB cluster #7656
• Enrich the error message of “GC life time is shorter than transaction duration” #7658
• Set the global system time zone when starting the TiDB cluster #7638

Compatibility

• Add the unsigned flag for the Year type #7542
• Fix the issue of configuring the result length of the Year type in the Prepare/Execute mode #7525
• Fix the issue of inserting zero timestamp in the Prepare/Execute mode #7506
• Fix the error handling issue of the integer division #7492
• Fix the compatibility issue when processing ComStmtSendLongData #7485
• Fix the error handling issue during the process of converting string to integer #7483
• Optimize the accuracy of values in the information_schema.columns_in_table table #7463
• Fix the compatibility issue when writing or updating the string type of data using the MariaDB client #7573
• Fix the compatibility issue of aliases of the returned value #7600
• Fix the issue that the NUMERIC_SCALE value of the float type is incorrect in the information_schema.COLUMNS table #7602
• Fix the issue that Parser reports an error when the single line comment is empty #7612

Expressions

• Check the value of max_allowed_packet in the insert function #7528
• Support the built-in function json_contains #7443
• Support the built-in function json_contains_path #7596
• Support the built-in function encode/decode #7622
• Fix the issue that some time related functions are not compatible with the MySQL behaviors in some cases #7636
• Fix the compatibility issue of parsing the time type of data in string #7654
• Fix the issue that the time zone is not considered when computing the default value of the DateTime data #7655

DML

• Set correct last_insert_id in the InsertOnDuplicateUpdate statement #7534
• Reduce the cases of updating the auto_increment_id counter #7515
• Optimize the error message of Duplicate Key #7495
• Fix the insert...select...on duplicate key update issue #7406
• Support the LOAD DATA IGNORE LINES statement #7576

DDL

• Add the DDL job type and the current schema version information in the monitor #7472
• Complete the design of the Admin Restore Table feature #7383
• Fix the issue that the default value of the Bit type exceeds 128 #7249
• Fix the issue that the default value of the Bit type cannot be NULL #7604
• Reduce the interval of checking CREATE TABLE/DATABASE in the DDL queue #7608
• Use the ddl/owner/resign HTTP interface ro release the DDL owner and start electing a new owner #7649

TiKV Go Client

• Support the issue that the Seek operation only obtains Key #7419

Table Partition (Experimental)

• Fix the issue that the Bigint type cannot be used as the partition key #7520
• Support the rollback operation when an issue occurs during adding an index in the partitioned table #7437

tidb-server v2.0.7

New Feature

• Add the PROCESSLIST table in information_schema #7286

Improvements

• Collect more details about SQL statement execution and output the information in the SLOW QUERY log #7364
• Drop the partition information in SHOW CREATE TABLE #7388
• Improve the execution efficiency of the ANALYZE statement by setting it to the RC isolation level and low priority #7500
• Speed up adding a unique index #7562
• Add an option of controlling the DDL concurrency #7563

Bug Fixes

• Fix the issue that USE INDEX(PRIMARY) cannot be used in a table whose primary key is an integer #7298
• Fix the issue that Merge Join and Index Join output incorrect results when the inner row is NULL #7301
• Fix the issue that Join outputs an incorrect result when the chunk size is set too small #7315
• Fix the panic issue caused by a statement of creating a table involving range column #7379
• Fix the issue that admin check table mistakenly reports an error of a time-type column #7457
• Fix the issue that the data with a default value current_timestamp cannot be queried using the = condition #7467
• Fix the issue that the zero-length parameter inserted by using the ComStmtSendLongData command is mistakenly parsed to NULL #7508
• Fix the issue that auto analyze is repeatedly executed in specific scenarios #7556
• Fix the issue that the parser cannot parse a single line comment ended with a newline character #7635