Some improvements in MySQL 8.0.24 Release Note

On April 20, MySQL 8.0 was updated to version 8.0.24. I read the release notes in the evening and sorted out some improvements. I recorded them here. You can download the corresponding version for testing later.

1. Connection Management

1. More detailed connection information

In previous versions, if a MySQL connection did not interact with the MySQL service for a long time, you would receive an output message saying MySQL Server has gone away, without any specific reason information.

The new version of MySQL Server will write the reason for the connection closing to the client before the connection is closed. The client can see more detailed information to analyze why the connection was closed.

2. The connection error message contains port

This is mainly a change in the connection error message, with an additional port information:

Before modification:
ERROR 2003 (HY000): Can't connect to MySQL server on '127.0.0.1' (10061)
After modification:
ERROR 2003 (HY000): Can't connect to MySQL server on '127.0.0.1:63333'

2. Improvements at the Optimizer Level

MySQL's query optimizer can now optimize subqueries involving derived tables by using outer joins. If the subquery already has explicit groupings, MySQL adds the extra groupings to the end of the existing grouping list.

Here are some examples:

SQL:
SELECT * FROM t1 WHERE (SELECT a FROM t2 WHERE t2.a=t1.a) > 0
After optimization:
SELECT t1.* FROM t1 LEFT OUTER JOIN (SELECT a, COUNT(*) AS ct FROM t2 GROUP BY a) AS derived ON t1.a = derived.a WHERE derived.a > 0.

3. Improvements in Functionality

1. The maximum value of AUTOEXTEND_SIZE is increased from 64MB to 4GB. This option was introduced in MySQL 8.0.23 and defines the maximum capacity that innodb can expand when the tablespace is full. This parameter can be used in create table, alter table, create tablespace, alter tablespace and other syntaxes.

2. The clone_donor_timeout_after_network_failure clone plugin variable defines the time that the donor in the clone plugin allows the recipient to reconnect and restart cloning after a network failure. This timeout was previously fixed at 5 minutes. The timeout can now be extended to 30 minutes to provide more time for network problems to resolve.

3. When the client application uses the set names syntax, if the character set is utf8, it will be displayed as utf8mb3 instead of utf8.

In fact, this change is expected. After all, utf8mb4 has gradually replaced utf8 and become the mainstream.

4. The value of allowlist can be updated during the operation of MGR, and new members can be added to the allowlist of MGR without restarting MGR.

5. The function of the --skip-slave-start parameter is to prevent the automatic startup of the replication relationship when the MySQL service is restarted. In previous versions, this parameter can be modified in my.cnf or by adding parameters in the command line. Both methods inevitably require logging in to the host server where the MySQL Server is located. In the new version of MySQL, this parameter will not be subject to this restriction and can be set using the set persist_only statement in the persistence configuration file. In this way, the modification can be performed from any client. There is no need to log in to the host machine where the MySQL service is located.

4. Performance Schema Optimization

There is not much research done on this area. If you are interested, you can check the official website.

5. Bug fixes

Overall, this version mainly fixes bugs in previous versions, fixing more than 200 bugs. There are not many updates to high-availability components such as MGR.

Speaking of bug fixes, here is a guide for choosing a minor version of MySQL:

Generally, check the release notes of the current MySQL version. If you find that the release notes of the current version have fewer bug fixes, it means that the previous version had fewer bugs. In this case, it is more appropriate to choose the previous MySQL version of the current version or the current version. The current version is preferred because the new version may have new features.

If the current version has many bug fixes, it means that there were many bugs in the previous version and it is not recommended to choose it. The current version has many bug fixes and cannot be guaranteed to be stable, so it is recommended to wait and see or look for a suitable MySQL version.

The above are the details of some improvements in the Release Note of MySQL 8.0.24 version. For more information about the improvements of MySQL Release Note, please pay attention to other related articles on 123WORDPRESS.COM!