TiDB 2.1.17 Release Notes

Release date: September 11, 2019

TiDB version: 2.1.17

TiDB Ansible version: 2.1.17

• New features

  • Add the WHERE clause in TiDB’s SHOW TABLE REGIONS syntax
  • Add the config-check feature in TiKV and PD to check the configuration items
  • Add the remove-tombstone command in pd-ctl to clear tombstone store records
  • Add the worker-count and txn-batch configuration items in Reparo to control the recovery speed

• Improvements

  • Optimize PD’s scheduling process by supporting actively pushing operators
  • Optimize TiKV’s starting process to reduce jitters caused by restarting nodes

• Changed behaviors

  • Change start ts in TiDB slow query logs from the last retry time to the first execution time
  • Replace the Index_ids field in TiDB slow query logs with the Index_names field to improve the usability of slow query logs
  • Add the split-region-max-num parameter in TiDB’s configuration files to modify the maximum number of Regions allowed by the SPLIT TABLE syntax, which is increased from 1,000 to 10,000 in the default configuration

TiDB

• SQL Optimizer
  • Fix the issue that the error message is not returned correctly when an error occurs during EvalSubquery building Executor #11811
  • Fix the issue that the query result might be incorrect when the number of rows in the outer table is greater than that in a single batch in Index Lookup Join; expand the functional scope of Index Lookup Join; UnionScan can be used as a subnode of IndexJoin #11843
  • Add the display of invalid keys (like invalid encoded key flag 252 ) in the SHOW STAT_BUCKETS syntax, for the situation where invalid keys might occur during the statistics feedback process #12098
• SQL Execution Engine
  • Fix some incorrect results (like select cast(13835058000000000000 as double)) caused by the number value that is first converted to UINT when the CAST function is converting the number value type #11712
  • Fix the issue that the calculation result might be incorrect when the dividend of the DIV calculation is a decimal and this calculation contains a negative number #11812
  • Add the ConvertStrToIntStrict function to fix the MySQL incompatibility issue caused by some strings being converted to the INT type when executing the SELECT/EXPLAIN statement #11892
  • Fix the issue that the Explain result might be incorrect caused by wrong configuration of stmtCtx when EXPLAIN ... FOR CONNECTION is used #11978
  • Fix the issue that the result returned by the unaryMinus function is incompatible with MySQL, caused by the non-decimal result when the integer result overflows #11990
  • Fix the issue that last_insert_id() might be incorrect, caused by the counting order when the LOAD DATA statement is being executed #11994
  • Fix the issue that last_insert_id() might be incorrect when the user writes auto-increment column data in an explicit-implicit mixed way #12001
  • Fix an over-quoted bug for the JSON_UNQUOTE function: only values enclosed by double quote marks (") should be unquoted. For example, the result of “SELECT JSON_UNQUOTE("\\\\")” should be “\\” (not changed) #12096
• Server
  • Change start ts recorded in slow query logs from the last retry time to the first execution time when retrying TiDB transactions #11878
  • Add the number of keys of a transaction in LockResolver to avoid the scan operation on the whole Region and reduce costs of resolving locking when the number of keys is reduced #11889
  • Fix the issue that the succ field value might be incorrect in slow query logs #11886
  • Replace the Index_ids filed in slow query logs with the Index_names field to improve the usability of slow query logs #12063
  • Fix the connection break issue caused by TiDB parsing - into EOF Error when Duration contains - (like select time(‘--’)) #11910
  • Remove an invalid Region from RegionCache more quickly to reduce the number of requests sent to this Region #11931
  • Fix the connection break issue caused by incorrectly handling the OOM panic issue when oom-action = "cancel" and OOM occurs in the Insert Into … Select syntax #12126
• DDL
  • Add the reverse scan interface for tikvSnapshot to efficiently query DDL history jobs. After using this interface, the execution time of ADMIN SHOW DDL JOBS is remarkably decreased #11789
  • Improve the CREATE TABLE ... PRE_SPLIT_REGION syntax: change the number of pre-splitting Regions from 2^(N-1) to 2^N when PRE_SPLIT_REGION = N #11797
  • Decrease the default parameter value for the background worker thread of the Add Index operation to avoid great impacts on online workloads #11875
  • Improve the SPLIT TABLE syntax behavior: generate N data Region(s) and one index Region when SPLIT TABLE ... REGIONS N is used to divide Regions #11929
  • Add the split-region-max-num parameter (10000 by default) in the configuration file to make the maximum number of Regions allowed by the SPLIT TABLE syntax adjustable #12080
  • Fix the issue that the CREATE TABLE clause cannot be parsed by the downstream MySQL, caused by uncommented PRE_SPLIT_REGIONS in this clause when the system writes the binlog #12121
  • Add the WHERE sub-clause in SHOW TABLE … REGIONS and SHOW TABLE .. INDEX … REGIONS #12124
• Monitor
  • Add the connection_transient_failure_count monitoring metric to count gRPC connection errors of tikvclient #12092

TiKV

• Fix the incorrect result of counting keys in a Region in some cases #5415
• Add the config-check option in TiKV to check whether the TiKV configuration item is valid #5391
• Optimize the starting process to reduce jitters caused by restarting nodes #5277
• Optimize the resolving locking process in some cases to speed up resolving locking for transactions #5339
• Optimize the get_txn_commit_info process to speed up committing transactions #5062
• Simplify Raft-related logs #5425
• Resolve the issue that TiKV exits abnormally in some cases #5441

PD

• Add the config-check option in PD to check whether the PD configuration item is valid #1725
• Add the remove-tombstone command in pd-ctl to support clearing tombstone store records #1705
• Support actively pushing operators to speed up scheduling #1686

Tools

• TiDB Binlog
  • Add worker-count and txn-batch configuration items in Reparo to control the recovery speed #746
  • Optimize the memory usage of Drainer to improve the parallel execution efficiency #735
  • Fix the bug that Pump cannot quit normally in some cases #739
  • Optimize the processing logic of LevelDB in Pump to improve the execution efficiency of GC #720
• TiDB Lightning
  • Fix the bug that tidb-lightning might crash caused by re-importing data from the checkpoint #239

TiDB Ansible

• Update the Spark version to 2.4.3, and update the TiSpark version to 2.2.0 that is compatible with Spark 2.4.3 #914, #919
• Fix the issue that there is a long waiting time when the remote machine password has expired #937, #948