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TiDB 2.1.18 Release Notes
/docs/dev/releases/release-2.1.18/
/docs/dev/releases/2.1.18/
TiDB 2.1.18 was released on November 4, 2019. The release includes various fixes and optimizations for SQL optimizer, SQL engine, server, DDL, monitor, and tools. Some notable improvements include support for using parameters in ORDER BY, GROUP BY, and LIMIT OFFSET, and adding new metrics for monitoring Add Index operation progress. The TiDB Ansible version 2.1.18 also includes updates and new monitoring items for TiDB Binlog.

TiDB 2.1.18 Release Notes

Release date: November 4, 2019

TiDB version: 2.1.18

TiDB Ansible version: 2.1.18

TiDB

  • SQL Optimizer
    • Fix the issue that invalid query ranges might appear when split by feedback #12172
    • Fix the issue that the privilege check is incorrect in point get plan #12341
    • Optimize execution performance of the select ... limit ... offset … statement by pushing the Limit operator down to the IndexLookUpReader execution logic #12380
    • Support using parameters in ORDER BY, GROUP BY and LIMIT OFFSET #12514
    • Fix the issue that IndexJoin on the partition table returns incorrect results #12713
    • Fix the issue that the str_to_date function in TiDB returns a different result from MySQL when the date string and the format string do not match #12757
    • Fix the issue that outer join is incorrectly converted to inner join when the cast function is included in the query conditions #12791
    • Fix incorrect expression passing in the join condition of AntiSemiJoin #12800
  • SQL Engine
    • Fix the incorrectly rounding of time (for example, 2019-09-11 11:17:47.999999666 should be rounded to 2019-09-11 11:17:48) #12259
    • Fix the issue that the duration by sql_type for the PREPARE statement is not shown in the monitoring record #12329
    • Fix the panic issue when the from_unixtime function handles null #12572
    • Fix the compatibility issue that when an invalid value is inserted as the YEAR type, the result is NULL instead of 0000 #12744
    • Improve the behavior of the AutoIncrement column when it is implicitly allocated, to keep it consistent with the default mode of MySQL auto-increment locking ("consecutive" lock mode): for the implicit allocation of multiple AutoIncrement IDs in a single-line Insert statement, TiDB guarantees the continuity of the allocated values. This improvement ensures that the JDBC getGeneratedKeys() method will get the correct results in any scenario #12619
    • Fix the issue that the query is hanged when HashAgg serves as a child node of Apply #12769
    • Fix the issue that the AND and OR logical expressions return incorrect results when it comes to type conversion #12813
  • Server
    • Fix the issue that the SLEEP() function is invalid for the KILL TIDB QUERY statements #12159
    • Fix the issue that no error is reported when AUTO_INCREMENT incorrectly allocates MAX int64 and MAX uint64 #12210
    • Fix the issue that the slow query logs are not recorded when the log level is ERROR #12373
    • Adjust the number of times that TiDB caches schema changes and corresponding changed table information from 100 to 1024, and support modification by using the tidb_max_delta_schema_count system variable #12515
    • Change the query start time from the point of "starting to execute" to "starting to compile" to make SQL statistics more accurate #12638
    • Add the record of set session autocommit in TiDB logs #12568
    • Record SQL query start time in SessionVars to prevent it from being reset during plan execution #12676
    • Support ? placeholder in ORDER BY, GROUP BY and LIMIT OFFSET #12514
    • Add the Prev_stmt field in slow query logs to output the previous statement when the last statement is COMMIT #12724
    • Record the last statement before COMMIT into the log when the COMMIT fails in an explicitly committed transaction #12747
    • Optimize the saving method of the previous statement when the TiDB server executes a SQL statement to improve performance #12751
    • Fix the panic issue caused by FLUSH PRIVILEGES statements under the skip-grant-table=true configuration #12816
    • Increase the default minimum step of applying AutoID from 1000 to 30000 to avoid performance bottleneck when there are many write requests in a short time #12891
    • Fix the issue that the failed Prepared statement is not print in the error log when TiDB panics #12954
    • Fix the issue that the COM_STMT_FETCH time record in slow query logs is inconsistent with that in MySQL #12953
    • Add an error code in the error message for write conflicts to quickly locate the cause #12878
  • DDL
    • Disallow dropping the AUTO INCREMENT attribute of a column by default. Modify the value of the tidb_allow_remove_auto_inc variable if you do need to drop this attribute. See System Variables for more details. #12146
    • Support multiple uniques when creating a unique index in the Create Table statement #12469
    • Fix a compatibility issue that if the foreign key constraint in CREATE TABLE statement has no schema, schema of the created table should be used instead of returning a No Database selected error #12678
    • Fix the issue that the invalid list index error is reported when executing ADMIN CANCEL DDL JOBS #12681
  • Monitor
    • Add types for backoff monitoring and supplement the backoff time that is not recorded before, such as the backoff time when committing #12326
    • Add a new metric to monitor Add Index operation progress #12389

PD

  • Improve the --help command output of pd-ctl #1772

Tools

  • TiDB Binlog
    • Fix the issue that ALTER DATABASE related DDL operations cause Drainer to exit abnormally #770
    • Support querying the transaction status information for Commit binlog to improve replication efficiency #761
    • Fix the issue that a Pump panic might occur when Drainer's start_ts is greater than Pump's largest commit_ts #759

TiDB Ansible

  • Add two monitoring items "queue size" and "query histogram" for TiDB Binlog #952
  • Update TiDB alerting rules #961
  • Check the configuration file before the deployment and upgrade #973
  • Add a new metric to monitor index speed in TiDB #987
  • Update TiDB Binlog monitoring dashboard to make it compatible with Grafana v4.6.3 #993