MySQL8.0 brief introduction
MySQL 5.7 To 8.0,Oracle The official jump Major Version Version number , What followed was that MySQL 8.0 A lot of major updates have been made on , On the way to enterprise database , new Data Dictionary Design , Support Atomic DDL, New version upgrade strategy , Strengthen security and account management ,InnoDB Enhancements, etc , At present, the small version has release To 8.0.16, New features are still coming out .
MySQL8.0 Version update
1. The data dictionary
MySQL 8.0 Abandoned Server Layer Defined FRM Files and other non transactional tables , A set of InnoDB Come on Save data dictionary , Support transaction features .
2. Atomic DDL
stay Data Dictionary On the basis of supporting transaction features ,8.0 Added one DDL log Dictionary table , To coordinate in
DDL In the process , For the data dictionary , Modification of file system and transaction system , Be atomic .
from 8.0.16 Start , For system table modification , Abandoned mysql_upgrade Tools , When the system restarts , upgrade .
4. Security and account management
Account number , from 8.0 Start , Support role Convenient management of permissions , And add multiple system permissions , They have been added respectively ROLE_EDGES,GLOBAL_GRANTS Two system tables ;mysql schema The following tables are related to permissions and users Change to InnoDB engine , Support transaction features , Ensure the atomicity of account management statements .
Certification ,caching_sha2_password As the default Authentication plugin, To improve safety , But be careful not to be with 8.0 Previous client For compatibility .
Link encryption , If it's compiled OpenSSL 1.1.1 And above ,MySQL 8.0 SSL Will support to TLSv1.3 edition .
System account number , stay 8.0.16 newly added SYSTEM_USER jurisdiction , Used to distinguish System account or ordinary account , It can be Manage by category .
5. Auto increment Persistence
stay InnoDB In the engine , Added a system table private to the engine innodb_dynamic_metadata, Keep it since you add value In this watch , Make changes to each table auto increment When it's worth it , All use redo log To protect , Doing it heckpoint When , Persist to this system table , Make sure that after the next restart ,auto increment Be able to recover from persistence Come back , And it is not affected by the transaction context rollback .
6. Deadlock detection
In the case of high concurrency ,InnoDB In the engine for Transaction lock Deadlock detection for , It's going to affect performance scale An important factor in ,8.0 A parameter is provided after innodb_deadlock_detect：https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_deadlock_detect, Deadlock detection to turn the engine on or off , Where the business is able to identify the relevant risks , Turn off deadlock detection , It can greatly improve the concurrent ability .
7. A temporary table
stay InnoDB In the engine , Temporary tables created by users will be unified to ibtmp In the temporary table space of the file ; For the temporary memory table generated during the system operation ,8.0 After the launch of the new TempTable engine , Support blob Field , It is better than memory ngine.
SELECT ... FOR SHARE and SELECT ... FOR UPDATE Added NOWAIT and SKIP LOCKED grammar , Reduce long and unnecessary blocking .
9. Instant add column
InnoDB Solved the long-term problems DBA Add fields to copy The whole table data problem . Now you can quickly add fields , Just modify the data dictionary , Instead of modifying the record itself in the table .
10. Parallel queries
InnoDB Currently supported in clustered index Parallel query on , Provide innodb_parallel_read_threads,https://dev.mysql.com/doc/refman/8.0/en/innodb-parameters.html#sysvar_innodb_parallel_read_threads, Parameter control session Within the degree of parallelism .
11. Redo Optimize
Redo The writing of has always been InnoDB The bottleneck in the case of high concurrency ,8.0 Start :
User threads can be concurrent copy redo Log to log buffer in
User threads can put dirty block Add to the dirty block list
Independent write threads complete redo The persistence of
12. Json To strengthen
stay Json On ,8.0 More sex , See MySQL 8.0 Of document.
13. Partial update on lob
InnoDB Continue to optimize partial update on lob data, For those that modify only a few bytes lob Field , Can be big Reduce undo data, And improve efficiency .
14. Optimizers are object related
1) Support invisible index, Convenient for users and DBA debugging statement.
2)descending indexes, Improve the efficiency of descending scanning .
3)Common table expressions, Support with Grammar complete .
4)Window functions, Add a lot of window functions
5)Regular expression, Redesigned support for regular expressions .
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