New changes released in MySQL8.0.3 RC version

MySQL 8.0.3 is about to be released, let’s take a look at what new changes there are

MySQL 8.0.3 is about to release the RC version, which indicates that the 8.0 version is closer to GA It's getting closer.

Let’s share some important new features and changes in version 8.0.3:

1. Directly Abolish query cache (should just If you close the entrance and compile the source code yourself, you can enable it again)

2. The query optimizer supports using the SET_VAR HINT syntax to modify certain session-level parameters directly in SQL. Options, such as:

   - SELECT /*+ SET_VAR(sort_buffer_size = 16M) */ name FROM people ORDER BY name;

   - INSERT /*+ SET_VAR(foreign_key_checks=OFF) */ INTO t2 VALUES(2);

   (This function is super practical. It can be modified directly in SQL. You don’t have to write another SQL and worry about affecting others)

3. The query optimizer now supports storing the histogram of each column's statistical results in the column_statistics data dictionary in order to construct the execution plan. With this histogram, it can be used to compare the column and the constant.

4. New flag bits in the query optimizer use_invisible_indexes are used to control the execution of the construction Whether to consider the factor of invisible indexes when planning

5. InnoDB has added a new backup-specific lock. In the past, if the InnoDB table was online hot standby and DML was performed at the same time, it might cause The snapshots of InnoDB files are inconsistent. With this backup lock, you don't have to worry. The backup lock usage is LOCK INSTANCE FOR BACKUP, UNLOCK INSTANCE, which requires BACKUP_ADMIN permission

6. InnoDB now supports the atomicity of table DDL, that is, DDL on the InnoDB table can also achieve transaction integrity, either failed and rolled back, or successfully submitted, without There is a partial success problem when DDL occurs. In addition, supports the crash-safe feature (this feature is very praised)

7. If it is delayed initialization group replication (GR, Group Replication ), that is, in single-primary mode, data can be written to the secondary node through the asynchronous replication channel, which is not allowed during normal initialization of the group replication plug-in (Bug #26314756, this is an internal BUG ID, we cannot see it Yes, don’t bother. But there is also the universal github, you can also see the relevant description, see: https://github.com/mysql/mysql-server/commit/acbf1d13ecd1d89557f8ca62116f06e8633dc90d)

8. Several views such as FILES, PARTITIONS, REFERENTIAL_CONSTRAINTS in the system library INFORMATION_SCHEMA have been re-implemented (this is not too specific, it may have something to do with all DDL being put into InnoDB, no longer Use FRM files to store DDL information)

9. Due to the transformation of the foreign key constraint lock function, the column renaming function on the parent table involving foreign key constraints will be temporarily disabled for a period of time (estimated in a few days) A small version can be used normally)

10. InnoDB general table space has new renaming syntax: ALTER TABLESPACE ... RENAME TO (As a MySQL DBA, it seems like nothing People who play with general table spaces may be more accustomed to using it after transferring from Oracle DBA)

11. On the slave node replicated by MySQL, the log_slave_updates option default value is changed to ON ( This is also more practical, making it easier to use the slave directly as a relay node) The global scope of the

12. option sql_log_bin is changed to a session-level scope, that is Modifying this option only affects this session and no longer affects the global situation (this option is generally used at the session level)

13. Option max_allowed_packet The default value is increased from 4M to 64M (This seems to be more practical)

14. Option event_scheduler The default value is changed from OFF to ON, so that the event scheduler function is enabled by default (I think the event function is quite good) , but it seems that not many people use event)

15. Option max_error_count The default value has been increased from 64 to 1024 (I don’t feel it)

16. Last one, the utf8mb4 character set adds a Russian check set (newly added utf8mb4_ru_0900_ai_ci, utf8mb4_ru_0900_as_cs two collations sets)

Let’s look forward to the release of 8.0.3!

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