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TiDB 3.0.0-rc.3 Release Notes
/docs/dev/releases/release-3.0.0-rc.3/
/docs/dev/releases/3.0.0-rc.3/
TiDB 3.0.0-rc.3 was released on June 21, 2019, with improvements in stability, usability, features, SQL optimizer, statistics, and execution engine. Fixes and new features were added to TiDB, PD, TiKV, and TiDB Ansible. Notable improvements include automatic loading statistics, manual splitting of table and index regions, and support for pessimistic transactions in TiKV.

TiDB 3.0.0-rc.3 Release Notes

Release date: June 21, 2019

TiDB version: 3.0.0-rc.3

TiDB Ansible version: 3.0.0-rc.3

Overview

On June 21, 2019, TiDB 3.0.0-rc.3 is released. The corresponding TiDB Ansible version is 3.0.0-rc.3. Compared with TiDB 3.0.0-rc.2, this release has greatly improved the stability, usability, features, the SQL optimizer, statistics, and the execution engine.

TiDB

  • SQL Optimizer

    • Remove the feature of collecting virtual generated column statistics #10629
    • Fix the issue that the primary key constant overflows during point queries #10699
    • Fix the issue that using uninitialized information in fast analyze causes panic #10691
    • Fix the issue that executing the create view statement using prepare causes panic because of wrong column information #10713
    • Fix the issue that the column information is not cloned when handling window functions #10720
    • Fix the wrong estimation for the selectivity rate of the inner table selection in index join #10854
    • Support automatic loading statistics when the stats-lease variable value is 0 #10811

  • Execution Engine

    • Fix the issue that resources are not correctly released when calling the Close function in StreamAggExec #10636
    • Fix the issue that the order of table_option and partition_options is incorrect in the result of executing the show create table statement for partitioned tables #10689
    • Improve the performance of admin show ddl jobs by supporting scanning data in reverse order #10687
    • Fix the issue that the result of the show grants statement in RBAC is incompatible with that of MySQL when this statement has the current_user field #10684
    • Fix the issue that UUIDs might generate duplicate values on multiple nodes #10712
    • Fix the issue that the show view privilege is not considered in explain #10635
    • Add the split table region statement to manually split the table Region to alleviate the hotspot issue #10765
    • Add the split index region statement to manually split the index Region to alleviate the hotspot issue #10764
    • Fix the incorrect execution issue when you execute multiple statements such as create user, grant, or revoke consecutively #10737
    • Add a blocklist to prohibit pushing down expressions to Coprocessor #10791
    • Add the feature of printing the expensive query log when a query exceeds the memory configuration limit #10849
    • Add the bind-info-lease configuration item to control the update time of the modified binding execution plan #10727
    • Fix the OOM issue in high concurrent scenarios caused by the failure to quickly release Coprocessor resources, resulted from the execdetails.ExecDetails pointer #10832
    • Fix the panic issue caused by the kill statement in some cases #10876

  • Server

    • Fix the issue that goroutine might leak when repairing GC #10683
    • Support displaying the host information in slow queries #10693
    • Support reusing idle links that interact with TiKV #10632
    • Fix the support for enabling the skip-grant-table option in RBAC #10738
    • Fix the issue that pessimistic-txn configuration goes invalid #10825
    • Fix the issue that the actively canceled ticlient requests are still retried #10850
    • Improve performance in the case where pessimistic transactions conflict with optimistic transactions #10881

  • DDL

    • Fix the issue that modifying charset using alter table causes the blob type change #10698
    • Add a feature to use SHARD_ROW_ID_BITS to scatter row IDs when the column contains an AUTO_INCREMENT attribute to alleviate the hotspot issue #10794
    • Prohibit adding stored generated columns by using the alter table statement #10808
    • Optimize the invalid survival time of DDL metadata to shorten the period during which the DDL operation is slower after cluster upgrade #10795

PD

  • Add the enable-two-way-merge configuration item to allow only one-way merging #1583
  • Add scheduling operations for AddLightLearner and AddLightPeer to make Region Scatter scheduling unrestricted by the limit mechanism #1563
  • Fix the issue of insufficient reliability because the data might only have one replica replication when the system is started #1581
  • Optimize configuration check logic to avoid configuration item errors #1585
  • Adjust the definition of the store-balance-rate configuration to the upper limit of the number of balance operators generated per minute #1591
  • Fix the issue that the store might have been unable to generate scheduled operations #1590

TiKV

  • Engine

    • Fix the issue that incomplete snapshots are generated in the system caused by the iterator not checking the status #4936
    • Fix the data loss issue caused by a delay of flushing data to the disk when receiving snapshots after a power failure in abnormal conditions #4850

  • Server

    • Add a feature to check the validity of the block-size configuration #4928
    • Add READ_INDEX-related monitoring metrics #4830
    • Add GC worker-related monitoring metrics #4922

  • Raftstore

    • Fix the issue that the cache of the local reader is not cleared correctly #4778
    • Fix the issue that the request delay might be increased when transferring the leader and changing conf #4734
    • Fix the issue that a stale command is wrongly reported #4682
    • Fix the issue that the command might be pending for a long time #4810
    • Fix the issue that files are damaged after a power failure, which is caused by a delay of synchronizing the snapshot file to the disk #4807, #4850

  • Coprocessor

    • Support Top-N in vector calculation #4827
    • Support Stream aggregation in vector calculation #4786
    • Support the AVG aggregate function in vector calculation #4777
    • Support the First aggregate function in vector calculation #4771
    • Support the SUM aggregate function in vector calculation #4797
    • Support the MAX/MIN aggregate function in vector calculation #4837
    • Support the Like expression in vector calculation #4747
    • Support the MultiplyDecimal expression in vector calculation #4849
    • Support the BitAnd/BitOr/BitXor expression in vector calculation #4724
    • Support the UnaryNot expression in vector calculation #4808

  • Transaction

    • Fix the issue that an error occurs caused by non-pessimistic locking conflicts in pessimistic transactions #4801, #4883
    • Reduce unnecessary calculation for optimistic transactions after enabling pessimistic transactions to improve the performance #4813
    • Add a feature of single statement rollback to ensure that the whole transaction does not need a rollback operation in a deadlock situation #4848
    • Add pessimistic transaction-related monitoring items #4852
    • Support using the ResolveLockLite command to resolve lightweight locks to improve the performance when severe conflicts exist #4882

  • tikv-ctl

    • Add the bad-regions command to support checking more abnormal conditions #4862
    • Add a feature of forcibly executing the tombstone command #4862

  • Misc

    • Add the dist_release compiling command #4841

Tools

  • TiDB Binlog
    • Fix the wrong offset issue caused by Pump not checking the returned value when it fails to write data #640
    • Add the advertise-addr configuration in Drainer to support the bridge mode in the container environment #634
    • Add the GetMvccByEncodeKey function in Pump to speed up querying the transaction status #632

TiDB Ansible

  • Add a monitoring item to predict the maximum QPS value of the cluster ("hide" by default) #f5cfa4d