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TiDB 3.0.0-rc.1 Release Notes
Release Date: May 10, 2019
TiDB version: 3.0.0-rc.1
TiDB Ansible version: 3.0.0-rc.1
Overview
On May 10, 2019, TiDB 3.0.0-rc.1 is released. The corresponding TiDB Ansible version is 3.0.0-rc.1. Compared with TiDB 3.0.0-beta.1, this release has greatly improved the stability, usability, features, the SQL optimizer, statistics, and the execution engine.
TiDB
SQL Optimizer
- Improve the accuracy of cost estimates by using order correlation between columns; introduce a heuristic parameter
tidb_opt_correlation_exp_factor
to control the preference for index scans for scenarios when correlation cannot be directly used for estimation. #9839 - Match more prefix columns of the indexes when extracting access conditions of composite indexes if there are relevant columns in the filter #10053
- Use the dynamic programming algorithm to specify the execution order of join operations when the number of tables participating in the join is less than the value of
tidb_opt_join_reorder_threshold
. #8816 - Match more prefix columns of the indexes in the inner tables that build the index join when using composite indexes as the access conditions #8471
- Improve the accuracy of row count estimation for single-column indexes with NULL values #9474
- Specially handle
GROUP_CONCAT
when eliminating aggregate functions during the logical optimization phase to prevent incorrect executions #9967 - Properly push the filter down to child nodes of the join operator if the filter is a constant #9848
- Specially handle some functions such as
RAND()
when pruning columns during the logical optimization phase to prevent incompatibilities with MySQL #10064 - Support
FAST ANALYZE
, which speeds up statistics collection by sampling the region instead of scanning the entire region. This feature is controlled by the variabletidb_enable_fast_analyze
. #10258 - Support SQL Plan Management, which ensures execution stability by performing execution plan binding for SQL statements. This feature is currently in beta and only supports bound execution plans for SELECT statements. It is not recommended to use it in the production environment. #10284
- Improve the accuracy of cost estimates by using order correlation between columns; introduce a heuristic parameter
Execution Engine
- Support tracking and controlling memory usage in three operators -
TableReader
,IndexReader
andIndexLookupReader
#10003 - Support showing more information about coprocessor tasks in the slow log such as the number of tasks in coprocessor, the average/longest/90% of execution/waiting time and the addresses of the TiKVs which take the longest execution time or waiting time #10165
- Support the prepared DDL statements with no placeholders #10144
- Support tracking and controlling memory usage in three operators -
Server
- Only allow the DDL owner to execute bootstrap when TiDB is started #10029
- Add the variable
tidb_skip_isolation_level_check
to prevent TiDB from reporting errors when setting the transaction isolation level to SERIALIZABLE #10065 - Merge the implicit commit time and the SQL execution time in the slow log #10294
- Support
GRANT ROLE
#9721 - Fix the
ConnectionEvent
error from thewhitelist
plugin that makes TiDB exit #9889 - Fix the issue of mistakenly adding read-only statements to the transaction history #9723
- Improve
kill
statements to stop SQL execution and release resources more quickly #9844 - Add a startup option
config-check
to check the validity of the configuration file #9855 - Fix the validity check of inserting NULL fields when the strict SQL mode is disabled #10161
DDL
- Add the
pre_split_regions
option forCREATE TABLE
statements; this option supports pre-splitting the Table Region when creating a table to avoid write hot spots caused by lots of writes after the table creation #10138 - Optimize the execution performance of some DDL statements #10170
- Add the warning that full-text indexes are not supported for
FULLTEXT KEY
#9821 - Fix the compatibility issue for the UTF8 and UTF8MB4 charsets in the old versions of TiDB #9820
- Fix the potential bug in
shard_row_id_bits
of a table #9868 - Fix the bug that the column charset is not changed after the table charset is changed #9790
- Fix a potential bug in
SHOW COLUMN
when usingBINARY
/BIT
as the column default value #9897 - Fix the compatibility issue in displaying
CHARSET
/COLLATION
descriptions in theSHOW FULL COLUMNS
statement #10007 - Fix the issue that the
SHOW COLLATIONS
statement only lists collations supported by TiDB #10186
- Add the
PD
- Upgrade ETCD #1452
- Unify the log format of etcd and PD server
- Fix the issue of failing to elect Leader by PreVote
- Support fast dropping the “propose” and “read” requests that are to fail to avoid blocking the subsequent requests
- Fix the deadlock issue of Lease
- Fix the issue that a hot store makes incorrect statistics of keys #1487
- Support forcibly rebuilding a PD cluster from a single PD node #1485
- Fix the issue that
regionScatterer
might generate an invalidOperatorStep
#1482 - Fix the too short timeout issue of the
MergeRegion
operator #1495 - Support giving high priority to hot region scheduling #1492
- Add the metrics for recording the time of handling TSO requests on the PD server side #1502
- Add the corresponding Store ID and Address to the metrics related to the store #1506
- Support the
GetOperator
service #1477 - Fix the issue that the error cannot be sent in the Heartbeat stream because the store cannot be found #1521
TiKV
Engine
- FIx the issue that may cause incorrect statistics on read traffic #4436
- Fix the issue that may cause prefix extractor panic when deleting a range #4503
- Optimize memory management to reduce memory allocation and copying for
Iterator Key Bound Option
#4537 - Fix the issue that failing to consider learner log gap may in some cases cause panic #4559
- Support
block cache
sharing among differentcolumn families
#4612
Server
RaftStore
- Support configurable
properties index distance
#4517
- Support configurable
Coprocessor
- Add batch index scan executor #4419
- Add vectorized evaluation framework #4322
- Add execution summary framework for batch executors #4433
- Check the maximum column when constructing the RPN expression to avoid invalid column offset that may cause evaluation panic #4481
- Add
BatchLimitExecutor
#4469 - Replace the original
futures-cpupool
withtokio-threadpool
in ReadPool to reduce context switch #4486 - Add batch aggregation framework #4533
- Add
BatchSelectionExecutor
#4562 - Add batch aggression function
AVG
#4570 - Add RPN function
LogicalAnd
#4575
Misc
- Support
tcmalloc
as a memory allocator #4370
- Support
Tools
TiDB Binlog
- Fix the replication abortion issue when binlog data for the primary key column of unsigned int type is negative #573
- Provide no compression option when downstream is
pb
; modify the downstream name frompb
tofile
#559 - Add the
storage.sync-log
configuration item in Pump that allows asynchronous flush on local storage #509 - Support traffic compression for communications between Pump and Drainer #495
- Add the
syncer.sql-mode
configuration item in Drainer to support parsing DDL queries in different sql-mode #511 - Add the
syncer.ignore-table
configuration item to support filtering out tables that do not require replication #520
Lightning
- Use row IDs or default column values to populate the column data missed in the dump file #170
- Fix the bug in Importer that import success may still be returned even if part of the SST failed to be imported #4566
- Support speed limit in Importer when uploading SST to TiKV #4412
- Support importing tables by size to reduce impacts on the cluster brought by Checksum and Analyze for big tables, and improve the success rate for Checksum and Analyze #156
- Improve Lightning’s SQL encoding performance by 50% by directly parsing data source file as types.Datum of TiDB and saving extra parsing overhead from the KV encoder #145
- Change log format to Unified Log Format #162
- Add some command line options for use when the configuration file is missing #157
sync-diff-inspector
TiDB Ansible
- Support more TiKV monitoring panels and update versions for Ansible, Grafana, and Prometheus #727
- Summary dashboard for viewing cluster status
- trouble_shooting dashboard for troubleshooting issues
- Details dashboard for developers to analyze issues
- Fix the bug that causes the downloading failure of TiDB Binlog of Kafka version #730
- Modify version limits on supported operating systems as CentOS 7.0+ and later, and Red Hat 7.0 and later #733
- Change version detection mode during the rolling update to multi-concurrent #736
- Update documentation links in README #740
- Remove redundant TiKV monitoring metrics; add new metrics for troubleshooting #735
- Optimize
table-regions.py
script to display leader distribution by table #739 - Update configuration file for Drainer #745
- Optimize TiDB monitoring with new panels that display latencies by SQL categories #747
- Update the Lightning configuration file and add the
tidb_lightning_ctl
script #1e946f8
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