- Introduction
- Concepts
- Architecture
- Key Features
- Horizontal Scalability
- MySQL Compatible Syntax
- Replicate from and to MySQL
- Distributed Transactions with Strong Consistency
- Cloud Native Architecture
- Minimize ETL with HTAP
- Fault Tolerance & Recovery with Raft
- Automatic Rebalancing
- Deployment and Orchestration with Ansible, Kubernetes, Docker
- JSON Support
- Spark Integration
- Read Historical Data Without Restoring from Backup
- Fast Import and Restore of Data
- Hybrid of Column and Row Storage
- SQL Plan Management
- Open Source
- Online Schema Changes
- How-to
- Get Started
- Deploy
- Hardware Recommendations
- From Binary Tarball
- Orchestrated Deployment
- Geographic Redundancy
- Data Migration with Ansible
- Configure
- Secure
- Transport Layer Security (TLS)
- Generate Self-signed Certificates
- Monitor
- Migrate
- Maintain
- Common Ansible Operations
- Backup and Restore
- Identify Abnormal Queries
- Scale
- Upgrade
- Troubleshoot
- Reference
- SQL
- MySQL Compatibility
- SQL Language Structure
- Data Types
- Functions and Operators
- Function and Operator Reference
- Type Conversion in Expression Evaluation
- Operators
- Control Flow Functions
- String Functions
- Numeric Functions and Operators
- Date and Time Functions
- Bit Functions and Operators
- Cast Functions and Operators
- Encryption and Compression Functions
- Information Functions
- JSON Functions
- Aggregate (GROUP BY) Functions
- Window Functions
- Miscellaneous Functions
- Precision Math
- List of Expressions for Pushdown
- SQL Statements
ADD COLUMN
ADD INDEX
ADMIN
ADMIN CANCEL DDL
ADMIN CHECKSUM TABLE
ADMIN CHECK [TABLE|INDEX]
ADMIN SHOW DDL [JOBS|QUERIES]
ALTER DATABASE
ALTER TABLE
ALTER USER
ANALYZE TABLE
BEGIN
CHANGE COLUMN
COMMIT
CREATE DATABASE
CREATE INDEX
CREATE ROLE
CREATE TABLE LIKE
CREATE TABLE
CREATE USER
CREATE VIEW
DEALLOCATE
DELETE
DESC
DESCRIBE
DO
DROP COLUMN
DROP DATABASE
DROP INDEX
DROP ROLE
DROP TABLE
DROP USER
DROP VIEW
EXECUTE
EXPLAIN ANALYZE
EXPLAIN
FLUSH PRIVILEGES
FLUSH STATUS
FLUSH TABLES
GRANT <privileges>
GRANT <role>
INSERT
KILL [TIDB]
LOAD DATA
LOAD STATS
MODIFY COLUMN
PREPARE
RECOVER TABLE
RENAME INDEX
RENAME TABLE
REPLACE
REVOKE <privileges>
REVOKE <role>
ROLLBACK
SELECT
SET DEFAULT ROLE
SET [NAMES|CHARACTER SET]
SET PASSWORD
SET ROLE
SET TRANSACTION
SET [GLOBAL|SESSION] <variable>
SHOW ANALYZE STATUS
SHOW CHARACTER SET
SHOW COLLATION
SHOW [FULL] COLUMNS FROM
SHOW CREATE TABLE
SHOW CREATE USER
SHOW DATABASES
SHOW ENGINES
SHOW ERRORS
SHOW [FULL] FIELDS FROM
SHOW GRANTS
SHOW INDEXES [FROM|IN]
SHOW INDEX [FROM|IN]
SHOW KEYS [FROM|IN]
SHOW PRIVILEGES
SHOW [FULL] PROCESSSLIST
SHOW SCHEMAS
SHOW STATUS
SHOW [FULL] TABLES
SHOW TABLE REGIONS
SHOW TABLE STATUS
SHOW [GLOBAL|SESSION] VARIABLES
SHOW WARNINGS
SPLIT REGION
START TRANSACTION
TRACE
TRUNCATE
UPDATE
USE
- Constraints
- Generated Columns
- Partitioning
- Character Set
- SQL Mode
- Views
- Configuration
- Security
- Transactions
- System Databases
- Errors Codes
- Supported Client Drivers
- Garbage Collection (GC)
- Performance
- Overview
- Understanding the Query Execution Plan
- The Blocklist of Optimization Rules and Expression Pushdown
- Introduction to Statistics
- TopN and Limit Push Down
- Optimizer Hints
- Check the TiDB Cluster Status Using SQL Statements
- Execution Plan Binding
- Statement Summary Table
- Tune TiKV
- Operating System Tuning
- Column Pruning
- Key Monitoring Metrics
- Alert Rules
- Best Practices
- TiSpark
- TiKV
- TiDB Binlog
- Tools
- TiDB in Kubernetes
- FAQs
- Support
- Contribute
- Releases
- All Releases
- v3.0
- v2.1
- v2.0
- v1.0
- Glossary
You are viewing the documentation of an older version of the TiDB database (TiDB v3.0).
TiDB 2.1 GA Release Notes
On November 30, 2018, TiDB 2.1 GA is released. See the following updates in this release. Compared with TiDB 2.0, this release has great improvements in stability, performance, compatibility, and usability.
TiDB
SQL Optimizer
Optimize the selection range of
Index Join
to improve the execution performanceOptimize the selection of outer table for
Index Join
and use the table with smaller estimated value of Row Count the as the outer tableOptimize Join Hint
TIDB_SMJ
so that Merge Join can be used even without proper index availableOptimize Join Hint
TIDB_INLJ
to specify the Inner table to JoinOptimize 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
andDELETE
statementSupport pushing down more functions:
ABS
/CEIL
/FLOOR
/IS TRUE
/IS FALSE
Optimize the constant folding algorithm for the
IF
andIFNULL
built-in functionsOptimize 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
andHash
aggregation operatorsImplement the parallel
Hash Aggregate
operators and improve the computing performance by 350% in some scenariosImplement the parallel
Project
operators and improve the performance by 74% in some scenariosRead the data of the Inner table and Outer table of
Hash Join
concurrently to improve the execution performanceOptimize the execution speed of the
REPLACE INTO
statement and increase the performance nearly by 10 timesOptimize 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
statementOptimize 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 AnalyzeAdd the
tidb_retry_limit
system variable to control the automatic retry times of transactionsSupport using
admin show slow
statement to obtain the slow queriesAdd the
tidb_slow_log_threshold
environment variable to set the threshold of slow log automatically
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 scenariosSupport the
select tidb_is_ddl_owner()
statement to facilitate deciding whether TiDB isDDL Owner
Support the
ALTER TABLE FORCE
syntaxSupport the
ALTER TABLE RENAME KEY TO
syntaxAdd the table name and database name in the output information of
admin show ddl jobs
Compatibility
Support more MySQL syntaxes
Make the
BIT
aggregate function support theALL
parameterSupport the
SHOW PRIVILEGES
statementSupport the
CHARACTER SET
syntax in theLOAD DATA
statementSupport the
IDENTIFIED WITH
syntax in theCREATE USER
statementSupport the
LOAD DATA IGNORE LINES
statementThe
Show ProcessList
statement returns more accurate information
Placement Driver (PD)
Optimize availability
Introduce the version control mechanism and support rolling update of the cluster compatibly
Enable
Raft PreVote
among PD nodes to avoid leader reelection when network recovers after network isolationEnable
raft learner
by default to lower the risk of unavailable data caused by machine failure during schedulingTSO allocation is no longer affected by the system clock going backwards
Support the
Region merge
feature to reduce the overhead brought by metadata
Optimize the scheduler
Optimize the processing of Down Store to speed up making up replicas
Optimize the hotspot scheduler to improve its adaptability when traffic statistics information jitters
Optimize the start of Coordinator to reduce the unnecessary scheduling caused by restarting PD
Optimize the issue that Balance Scheduler schedules small Regions frequently
Optimize Region merge to consider the number of rows within the Region
Improve PD simulator to simulate the scheduling scenarios
API and operation tools
Add the
GetPrevRegion
interface to support theTiDB reverse scan
featureAdd the
BatchSplitRegion
interface to speed up TiKV Region splittingAdd the
GCSafePoint
interface to support distributed GC in TiDBAdd the
GetAllStores
interface, to support distributed GC in TiDB
pd-ctl supports:
- pd-recover doesn't need to provide the
max-replica
parameter
Metrics
Add related metrics for
Filter
Add metrics about etcd Raft state machine
Performance
Optimize the performance of Region heartbeat to reduce the memory overhead brought by heartbeats
Optimize the Region tree performance
Optimize the performance of computing hotspot statistics
TiKV
Coprocessor
Add more built-in functions
Add Coprocessor
ReadPool
to improve the concurrency in processing the requestsFix the time function parsing issue and the time zone related issues
Optimize the memory usage for pushdown aggregation computing
Transaction
Optimize the read logic and memory usage of MVCC to improve the performance of the scan operation and the performance of full table scan is 1 time better than that in TiDB 2.0
Fold the continuous Rollback records to ensure the read performance
Add the
UnsafeDestroyRange
API to support to collecting space for the dropping table/indexSeparate the GC module to reduce the impact on write
Add the
upper bound
support in thekv_scan
command
Raftstore
Improve the snapshot writing process to avoid RocksDB stall
Add the
LocalReader
thread to process read requests and reduce the delay for read requestsSupport
BatchSplit
to avoid large Region brought by large amounts of writeSupport
Region Split
according to statistics to reduce the I/O overheadSupport
Region Split
according to the number of keys to improve the concurrency of index scanImprove the Raft message process to avoid unnecessary delay brought by
Region Split
Enable the
PreVote
feature by default to reduce the impact of network isolation on services
Storage Engine
Fix the
CompactFiles
bug in RocksDB and reduce the impact on importing data using LightningUpgrade RocksDB to v5.15 to fix the possible issue of snapshot file corruption
Improve
IngestExternalFile
to avoid the issue that flush could block write
tikv-ctl
The
compact
command supports specifying whether to compact data in the bottommost level
Tools
Fast full import of large amounts of data: TiDB Lightning
Support new TiDB Binlog
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, check if there is any ongoing DDL operation, especially the time consuming
Add Index
operation, because the DDL operations slow down the upgrading process. If there is ongoing DDL operation, wait for the DDL operation finishes and then roll update.