Mysql：8.0.19：Upgrading Mysql：升级

2.11 Upgrading MySQL

2.11.1 Before You Begin
2.11.2 Upgrade Paths
2.11.3 What the MySQL Upgrade Process Upgrades
2.11.4 Changes in MySQL 8.0
2.11.5 Preparing Your Installation for Upgrade
2.11.6 Upgrading MySQL Binary or Package-based Installations on Unix/Linux
2.11.7 Upgrading MySQL with the MySQL Yum Repository
2.11.8 Upgrading MySQL with the MySQL APT Repository
2.11.9 Upgrading MySQL with the MySQL SLES Repository
2.11.10 Upgrading MySQL on Windows
2.11.11 Upgrading a Docker Installation of MySQL
2.11.12 Upgrade Troubleshooting
2.11.13 Rebuilding or Repairing Tables or Indexes
2.11.14 Copying MySQL Databases to Another Machine

This section describes the steps to upgrade a MySQL installation.

Upgrading is a common procedure, as you pick up bug fixes within the same MySQL release series or significant features between major MySQL releases. You perform this procedure first on some test systems to make sure everything works smoothly, and then on the production systems.

Note

In the following discussion, MySQL commands that must be run using a MySQL account with administrative privileges include -u root on the command line to specify the MySQL root user. Commands that require a password for root also include a -p option. Because -p is followed by no option value, such commands prompt for the password. Type the password when prompted and press Enter.

SQL statements can be executed using the mysql command-line client (connect as root to ensure that you have the necessary privileges).

2.11.1 Before You Begin

Review the information in this section before upgrading. Perform any recommended actions.

2.11.2 Upgrade Paths

  • Upgrade from MySQL 5.7 to 8.0 is supported. However, upgrade is only supported between General Availability (GA) releases. For MySQL 8.0, it is required that you upgrade from a MySQL 5.7 GA release (5.7.9 or higher). Upgrades from non-GA releases of MySQL 5.7 are not supported.

  • Upgrading to the latest release is recommended before upgrading to the next version. For example, upgrade to the latest MySQL 5.7 release before upgrading to MySQL 8.0.

  • Upgrade that skips versions is not supported. For example, upgrading directly from MySQL 5.6 to 8.0 is not supported.

  • Once a release series reaches General Availability (GA) status, upgrade within the release series (from one GA version to another GA version) is supported. For example, upgrading from MySQL 8.0.x to 8.0.y is supported. (Upgrade involving development-status non-GA releases is not supported.) Skipping a release is also supported. For example, upgrading from MySQL 8.0.x to 8.0.z is supported. MySQL 8.0.11 is the first GA status release within the MySQL 8.0 release series.

2.11.3 What the MySQL Upgrade Process Upgrades

Installing a new version of MySQL may require upgrading these parts of the existing installation:

  • The mysql system schema, which contains tables that store information required by the MySQL server as it runs (see Section 5.3, “The mysql System Schema”). mysql schema tables fall into two broad categories:

    • Data dictionary tables, which store database object metadata.

    • System tables (that is, the remaining non-data dictionary tables), which are used for other operational purposes.

  • Other schemas, some of which are built in and may be considered “owned” by the server, and others which are not:

    • The Performance Schema, INFORMATION_SCHEMA, ndbinfo, and sys schema.

    • User schemas.

Two distinct version numbers are associated with parts of the installation that may require upgrading:

  • The data dictionary version. This applies to the data dictionary tables.

  • The server version, also known as the MySQL version. This applies to the system tables and objects in other schemas.

In both cases, the actual version applicable to the existing MySQL installation is stored in the data dictionary, and the current expected version is compiled into the new version of MySQL. When an actual version is lower than the current expected version, those parts of the installation associated with that version must be upgraded to the current version. If both versions indicate an upgrade is needed, the data dictionary upgrade must occur first.

As a reflection of the two distinct versions just mentioned, the upgrade occurs in two steps:

  • Step 1: Data dictionary upgrade.

    This step upgrades:

    • The data dictionary tables in the mysql schema. If the actual data dictionary version is lower than the current expected version, the server creates data dictionary tables with updated definitions, copies persisted metadata to the new tables, atomically replaces the old tables with the new ones, and reinitializes the data dictionary.

    • The Performance Schema, INFORMATION_SCHEMA, and ndbinfo.

  • Step 2: Server upgrade.

    This step comprises all other upgrade tasks. If the server version of the existing MySQL installation is lower than that of the new installed MySQL version, everything else must be upgraded:

    • The system tables in the mysql schema (the remaining non-data dictionary tables).

    • The sys schema.

    • User schemas.

The data dictionary upgrade (step 1) is the responsibility of the server, which performs this task as necessary at startup unless invoked with an option that prevents it from doing so. The option is --upgrade=NONE as of MySQL 8.0.16, --no-dd-upgrade prior to MySQL 8.0.16.

If the data dictionary is out of date but the server is prevented from upgrading it, the server will not run and exits with an error. For example:

[ERROR] [MY-013381] [Server] Server shutting down because upgrade is
required, yet prohibited by the command line option '--upgrade=NONE'.
[ERROR] [MY-010334] [Server] Failed to initialize DD Storage Engine
[ERROR] [MY-010020] [Server] Data Dictionary initialization failed.

Some changes to the responsibility for step 2 occurred in MySQL 8.0.16:

  • Prior to MySQL 8.0.16, mysql_upgrade upgrades the Performance Schema, the INFORMATION_SCHEMA, and the objects described in step 2. The DBA is expected to invoke mysql_upgrade manually after starting the server.

  • As of MySQL 8.0.16, the server performs all tasks previously handled by mysql_upgrade. Although upgrading remains a two-step operation, the server performs them both, resulting in a simpler process.

Depending on the version of MySQL to which you are upgrading, the instructions in In-Place Upgrade and Logical Upgrade indicate whether the server performs all upgrade tasks or whether you must also invoke mysql_upgrade after server startup.

Note

Because the server upgrades the Performance Schema, INFORMATION_SCHEMA, and the objects described in step 2 as of MySQL 8.0.16, mysql_upgrade is unneeded and is deprecated as of that version, and will be removed in a future MySQL version.

Most aspects of what occurs during step 2 are the same prior to and as of MySQL 8.0.16, although different command options may be needed to achieve a particular effect.

As of MySQL 8.0.16, the --upgrade server option controls whether and how the server performs an automatic upgrade at startup:

  • With no option or with --upgrade=AUTO, the server upgrades anything it determines to be out of date (steps 1 and 2).

  • With --upgrade=NONE, the server upgrades nothing (skips steps 1 and 2), but also exits with an error if the data dictionary must be upgraded. It is not possible to run the server with an out-of-date data dictionary; the server insists on either upgrading it or exiting.

  • With --upgrade=MINIMAL, the server upgrades the data dictionary, the Performance Schema, and the INFORMATION_SCHEMA, if necessary (step 1). Note that following an upgrade with this option, Group Replication cannot be started, because system tables on which the replication internals depend are not updated, and reduced functionality might also be apparent in other areas.

  • With --upgrade=FORCE, the server upgrades the data dictionary, the Performance Schema, and the INFORMATION_SCHEMA, if necessary (step 1), and forces an upgrade of everything else (step 2). Expect server startup to take longer with this option because the server checks all objects in all schemas.

FORCE is useful to force step 2 actions to be performed if the server thinks they are not necessary. One way that FORCE differs from AUTO is that with FORCE, the server re-creates system tables such as help tables or time zone tables if they are missing.

The following list shows upgrade commands prior to MySQL 8.0.16 and the equivalent commands for MySQL 8.0.16 and higher:

Prior to MySQL 8.0.16, certain mysql_upgrade options affect the actions it performs. The following table shows which server --upgrade option values to use as of MySQL 8.0.16 to achieve similar effects. (These are not necessarily exact equivalents because a given --upgrade option value may have additional effects.)

mysql_upgrade OptionServer Option
--skip-sys-schema --upgrade=NONE or --upgrade=MINIMAL
--upgrade-system-tables --upgrade=NONE or --upgrade=MINIMAL
--force --upgrade=FORCE

Additional notes about what occurs during upgrade step 2:

  • Step 2 installs the sys schema if it is not installed, and upgrades it to the current version otherwise. An error occurs if a sys schema exists but has no version view, on the assumption that its absence indicates a user-created schema:

    A sys schema exists with no sys.version view. If
you have a user created sys schema, this must be renamed for the
upgrade to succeed.

    To upgrade in this case, remove or rename the existing sys schema first. Then perform the upgrade procedure again. (It may be necessary to force step 2.)

    To prevent the sys schema check:

    • As of MySQL 8.0.16: Start the server with the --upgrade=NONE or --upgrade=MINIMAL option.

    • Prior to MySQL 8.0.16: Invoke mysql_upgrade with the --skip-sys-schema option.

  • Step 2 processes all tables in all user schemas as necessary. Table checking might take a long time to complete. Each table is locked and therefore unavailable to other sessions while it is being processed. Check and repair operations can be time-consuming, particularly for large tables. Table checking uses the FOR UPGRADE option of the CHECK TABLE statement. For details about what this option entails, see Section 13.7.3.2, “CHECK TABLE Statement”.

    To prevent table checking:

    To force table checking:

    • As of MySQL 8.0.16: Start the server with the --upgrade=FORCE option.

    • Prior to MySQL 8.0.16: Invoke mysql_upgrade with the --force option.

  • Step 2 saves the MySQL version number in a file named mysql_upgrade_info in the data directory.

    To ignore the mysql_upgrade_info file and perform the check regardless:

    • As of MySQL 8.0.16: Start the server with the --upgrade=FORCE option.

    • Prior to MySQL 8.0.16: Invoke mysql_upgrade with the --force option.

    Note

    The mysql_upgrade_info file is deprecated and will be removed in a future MySQL version.

  • Step 2 marks all checked and repaired tables with the current MySQL version number. This ensures that the next time upgrade checking occurs with the same version of the server, it can be determined whether there is any need to check or repair a given table again.

  • Step 2 upgrades the system tables to ensure that they have the current structure. This is true whether the server or mysql_upgrade performs the step. With respect to the content of the help tables and time zone tables, mysql_upgrade does not load either type of table, whereas the server loads the help tables, but not the time zone tables. (That is, prior to MySQL 8.0.16, the server loads the help tables only at data directory initialization time. As of MySQL 8.0.16, it loads the help tables at initialization and upgrade time.) The procedure for loading time zone tables is platform dependent and requires decision making by the DBA, so it cannot be done automatically.

2.11.4 Changes in MySQL 8.0

Before upgrading to MySQL 8.0, review the changes described in this section to identify those that apply to your current MySQL installation and applications. Perform any recommended actions.

Changes marked as Incompatible change are incompatibilities with earlier versions of MySQL, and may require your attention before upgrading. Our aim is to avoid these changes, but occasionally they are necessary to correct problems that would be worse than an incompatibility between releases. If an upgrade issue applicable to your installation involves an incompatibility, follow the instructions given in the description.

Data Dictionary Changes

MySQL Server 8.0 incorporates a global data dictionary containing information about database objects in transactional tables. In previous MySQL series, dictionary data was stored in metadata files and nontransactional system tables. As a result, the upgrade procedure requires that you verify the upgrade readiness of your installation by checking specific prerequisites. For more information, see Section 2.11.5, “Preparing Your Installation for Upgrade”. A data dictionary-enabled server entails some general operational differences; see Section 14.7, “Data Dictionary Usage Differences”.

caching_sha2_password as the Preferred Authentication Plugin

The caching_sha2_password and sha256_password authentication plugins provide more secure password encryption than the mysql_native_password plugin, and caching_sha2_password provides better performance than sha256_password. Due to these superior security and performance characteristics of caching_sha2_password, it is as of MySQL 8.0 the preferred authentication plugin, and is also the default authentication plugin rather than mysql_native_password. This change affects both the server and the libmysqlclient client library:

  • For the server, the default value of the default_authentication_plugin system variable changes from mysql_native_password to caching_sha2_password.

    This change applies only to new accounts created after installing or upgrading to MySQL 8.0 or higher. For accounts already existing in an upgraded installation, their authentication plugin remains unchanged. Existing users who wish to switch to caching_sha2_password can do so using the ALTER USER statement:

    ALTER USER user
  IDENTIFIED WITH caching_sha2_password
  BY 'password';

  • The libmysqlclient library treats caching_sha2_password as the default authentication plugin rather than mysql_native_password.

The following sections discuss the implications of the more prominent role of caching_sha2_password:

caching_sha2_password Compatibility Issues and Solutions
Important

If your MySQL installation must serve pre-8.0 clients and you encounter compatibility issues after upgrading to MySQL 8.0 or higher, the simplest way to address those issues and restore pre-8.0 compatibility is to reconfigure the server to revert to the previous default authentication plugin (mysql_native_password). For example, use these lines in the server option file:

[mysqld]
default_authentication_plugin=mysql_native_password

That setting enables pre-8.0 clients to connect to 8.0 servers until such time as the clients and connectors in use at your installation are upgraded to know about caching_sha2_password. However, the setting should be viewed as temporary, not as a long term or permanent solution, because it causes new accounts created with the setting in effect to forego the improved authentication security provided by caching_sha2_password.

The use of caching_sha2_password offers more secure password hashing than mysql_native_password (and consequent improved client connection authentication). However, it also has compatibility implications that may affect existing MySQL installations:

  • Clients and connectors that have not been updated to know about caching_sha2_password may have trouble connecting to a MySQL 8.0 server configured with caching_sha2_password as the default authentication plugin, even to use accounts that do not authenticate with caching_sha2_password. This issue occurs because the server specifies the name of its default authentication plugin to clients. If a client or connector is based on a client/server protocol implementation that does not gracefully handle an unrecognized default authentication plugin, it may fail with an error such as one of these:

    Authentication plugin 'caching_sha2_password' is not supported
    Authentication plugin 'caching_sha2_password' cannot be loaded:
dlopen(/usr/local/mysql/lib/plugin/caching_sha2_password.so, 2):
image not found
    Warning: mysqli_connect(): The server requested authentication
method unknown to the client [caching_sha2_password]

    For information about writing connectors to gracefully handle requests from the server for unknown default authentication plugins, see Authentication Plugin Connector-Writing Considerations.

  • Clients that use an account that authenticates with caching_sha2_password must use either a secure connection (made using TCP using TLS/SSL credentials, a Unix socket file, or shared memory), or an unencrypted connection that supports password exchange using an RSA key pair. This security requirement does not apply to mysql_native_passsword, so the switch to caching_sha2_password may require additional configuration (see Section 6.4.1.2, “Caching SHA-2 Pluggable Authentication”). However, client connections in MySQL 8.0 prefer use of TLS/SSL by default, so clients that already conform to that preference may need no additional configuration.

  • Clients and connectors that have not been updated to know about caching_sha2_password cannot connect to accounts that authenticate with caching_sha2_password because they do not recognize this plugin as valid. (This is a particular instance of how client/server authentication plugin compatibility requirements apply, as discussed at Authentication Plugin Client/Server Compatibility.) To work around this issue, relink clients against libmysqlclient from MySQL 8.0 or higher, or obtain an updated connector that recognizes caching_sha2_password.

  • Because caching_sha2_password is also now the default authentication plugin in the libmysqlclient client library, authentication requires an extra round trip in the client/server protocol for connections from MySQL 8.0 clients to accounts that use mysql_native_password (the previous default authentication plugin), unless the client program is invoked with a --default-auth=mysql_native_password option.

The libmysqlclient client library for pre-8.0 MySQL versions is able to connect to MySQL 8.0 servers (except for accounts that authenticate with caching_sha2_password). That means pre-8.0 clients based on libmysqlclient should also be able to connect. Examples:

  • Standard MySQL clients such as mysql and mysqladmin are libmysqlclient-based.

  • The DBD::mysql driver for Perl DBI is libmysqlclient-based.

  • MySQL Connector/Python has a C Extension module that is libmysqlclient-based. To use it, include the use_pure=False option at connect time.

When an existing MySQL 8.0 installation is upgraded to MySQL 8.0.4 or higher, some older libmysqlclient-based clients may “automatically” upgrade if they are dynamically linked, because they use the new client library installed by the upgrade. For example, if the DBD::mysql driver for Perl DBI uses dynamic linking, it can use the libmysqlclient in place after an upgrade to MySQL 8.0.4 or higher, with this result:

  • Prior to the upgrade, DBI scripts that use DBD::mysql can connect to a MySQL 8.0 server, except for accounts that authenticate with caching_sha2_password.

  • After the upgrade, the same scripts become able to use caching_sha2_password accounts as well.

However, the preceding results occur because libmysqlclient instances from MySQL 8.0 installations prior to 8.0.4 are binary compatible: They both use a shared library major version number of 21. For clients linked to libmysqlclient from MySQL 5.7 or older, they link to a shared library with a different version number that is not binary compatible. In this case, the client must be recompiled against libmysqlclient from 8.0.4 or higher for full compatibility with MySQL 8.0 servers and caching_sha2_password accounts.

MySQL Connector/J 5.1 through 8.0.8 is able to connect to MySQL 8.0 servers, except for accounts that authenticate with caching_sha2_password. (Connector/J 8.0.9 or higher is required to connect to caching_sha2_password accounts.)

Clients that use an implementation of the client/server protocol other than libmysqlclient may need to be upgraded to a newer version that understands the new authentication plugin. For example, in PHP, MySQL connectivity usually is based on mysqlnd, which currently does not know about caching_sha2_password. Until an updated version of mysqlnd is available, the way to enable PHP clients to connect to MySQL 8.0 is to reconfigure the server to revert to mysql_native_password as the default authentication plugin, as previously discussed.

If a client or connector supports an option to explicitly specify a default authentication plugin, use it to name a plugin other than caching_sha2_password. Examples:

  • Some MySQL clients support a --default-auth option. (Standard MySQL clients such as mysql and mysqladmin support this option but can successfully connect to 8.0 servers without it. However, other clients may support a similar option. If so, it is worth trying it.)

  • Programs that use the libmysqlclient C API can call the mysql_options() function with the MYSQL_DEFAULT_AUTH option.

  • MySQL Connector/Python scripts that use the native Python implementation of the client/server protocol can specify the auth_plugin connection option. (Alternatively, use the Connector/Python C Extension, which is able to connect to MySQL 8.0 servers without the need for auth_plugin.)

caching_sha2_password-Compatible Clients and Connectors

If a client or connector is available that has been updated to know about caching_sha2_password, using it is the best way to ensure compatibility when connecting to a MySQL 8.0 server configured with caching_sha2_password as the default authentication plugin.

These clients and connectors have been upgraded to support caching_sha2_password:

  • The libmysqlclient client library in MySQL 8.0 (8.0.4 or higher). Standard MySQL clients such as mysql and mysqladmin are libmysqlclient-based, so they are compatible as well.

  • The libmysqlclient client library in MySQL 5.7 (5.7.23 or higher). Standard MySQL clients such as mysql and mysqladmin are libmysqlclient-based, so they are compatible as well.

  • MySQL Connector/C++ 1.1.11 or higher or 8.0.7 or higher.

  • MySQL Connector/J 8.0.9 or higher.

  • MySQL Connector/NET 8.0.10 or higher (through the classic MySQL protocol).

  • MySQL Connector/Node.js 8.0.9 or higher.

  • PHP: the X DevAPI PHP extension (mysql_xdevapi) supports caching_sha2_password.

    PHP: the PDO_MySQL and ext/mysqli extensions do not support caching_sha2_password. In addition, when used with PHP versions before 7.1.16 and PHP 7.2 before 7.2.4, they fail to connect with default_authentication_plugin=caching_sha2_password even if caching_sha2_password is not used.

caching_sha2_password and the root Administrative Account

For upgrades to MySQL 8.0, the authentication plugin existing accounts remains unchanged, including the plugin for the 'root'@'localhost' administrative account.

For new MySQL 8.0 installations, when you initialize the data directory (using the instructions at Section 2.10.1, “Initializing the Data Directory”), the 'root'@'localhost' account is created, and that account uses caching_sha2_password by default. To connect to the server following data directory initialization, you must therefore use a client or connector that supports caching_sha2_password. If you can do this but prefer that the root account use mysql_native_password after installation, install MySQL and initialize the data directory as you normally would. Then connect to the server as root and use ALTER USER as follows to change the account authentication plugin and password:

ALTER USER 'root'@'localhost'
  IDENTIFIED WITH mysql_native_password
  BY 'password';

If the client or connector that you use does not yet support caching_sha2_password, you can use a modified data directory-initialization procedure that associates the root account with mysql_native_password as soon as the account is created. To do so, use either of these techniques:

caching_sha2_password and Replication

In replication scenarios for which all servers have been upgraded to MySQL 8.0.4 or higher, slave/replica connections to master/primary servers can use accounts that authenticate with caching_sha2_password. For such connections, the same requirement applies as for other clients that use accounts that authenticate with caching_sha2_password: Use a secure connection or RSA-based password exchange.

To connect to a caching_sha2_password account for master/slave replication:

  • Use any of the following CHANGE MASTER TO options:

    MASTER_SSL = 1
GET_MASTER_PUBLIC_KEY = 1
MASTER_PUBLIC_KEY_PATH='path to RSA public key file'

  • Alternatively, you can use the RSA public key-related options if the required keys are supplied at server startup.

To connect to a caching_sha2_password account for Group Replication:

  • For MySQL built using OpenSSL, set any of the following system variables:

    SET GLOBAL group_replication_recovery_use_ssl = ON;
SET GLOBAL group_replication_recovery_get_public_key = 1;
SET GLOBAL group_replication_recovery_public_key_path = 'path to RSA public key file';

  • Alternatively, you can use the RSA public key-related options if the required keys are supplied at server startup.

Configuration Changes

  • Incompatible change: A MySQL storage engine is now responsible for providing its own partitioning handler, and the MySQL server no longer provides generic partitioning support. InnoDB and NDB are the only storage engines that provide a native partitioning handler that is supported in MySQL 8.0. A partitioned table using any other storage engine must be altered—either to convert it to InnoDB or NDB, or to remove its partitioning—before upgrading the server, else it cannot be used afterwards.

    For information about converting MyISAM tables to InnoDB, see Section 15.6.1.5, “Converting Tables from MyISAM to InnoDB”.

    A table creation statement that would result in a partitioned table using a storage engine without such support fails with an error (ER_CHECK_NOT_IMPLEMENTED) in MySQL 8.0. If you import databases from a dump file created in MySQL 5.7 (or earlier) using mysqldump into a MySQL 8.0 server, you must make sure that any statements creating partitioned tables do not also specify an unsupported storage engine, either by removing any references to partitioning, or by specifying the storage engine as InnoDB or allowing it to be set as InnoDB by default.

    Note

    The procedure given at Section 2.11.5, “Preparing Your Installation for Upgrade”, describes how to identify partitioned tables that must be altered before upgrading to MySQL 8.0.

    See Section 23.6.2, “Partitioning Limitations Relating to Storage Engines”, for further information.

  • Incompatible change: Several server error codes are not used and have been removed (for a list, see Features Removed in MySQL 8.0). Applications that test specifically for any of them should be updated.

  • Important change: The default character set has changed from latin1 to utf8mb4. These system variables are affected:

    As a result, the default character set and collation for new objects differ from previously unless an explicit character set and collation are specified. This includes databases and objects within them, such as tables, views, and stored programs. Assuming that the previous defaults were used, one way to preserve them is to start the server with these lines in the my.cnf file:

    [mysqld]
character_set_server=latin1
collation_server=latin1_swedish_ci

    In a replicated setting, when upgrading from MySQL 5.7 to 8.0, it is advisable to change the default character set back to the character set used in MySQL 5.7 before upgrading. After the upgrade is completed, the default character set can be changed to utf8mb4.

  • Incompatible change: As of MySQL 8.0.11, it is prohibited to start the server with a lower_case_table_names setting that is different from the setting used when the server was initialized. The restriction is necessary because collations used by various data dictionary table fields are based on the lower_case_table_names setting that was defined when the server was initialized, and restarting the server with a different setting would introduce inconsistencies with respect to how identifiers are ordered and compared.

Server Changes

  • In MySQL 8.0.11, several deprecated features related to account management have been removed, such as use of the GRANT statement to modify nonprivilege characteristics of user accounts, the NO_AUTO_CREATE_USER SQL mode, the PASSWORD() function, and the old_passwords system variable.

    Replication from MySQL 5.7 to 8.0 of statements that refer to these removed features can cause replication failure. Applications that use any of the removed features should be revised to avoid them and use alternatives when possible, as described in Features Removed in MySQL 8.0.

    To avoid a startup failure on MySQL 8.0, remove any instance of NO_AUTO_CREATE_USER from sql_mode system variable settings in MySQL option files.

    Loading a dump file that includes the NO_AUTO_CREATE_USER SQL mode in stored program definitions into a MySQL 8.0 server causes a failure. As of MySQL 5.7.24 and MySQL 8.0.13, mysqldump removes NO_AUTO_CREATE_USER from stored program definitions. Dump files created with an earlier version of mysqldump must be modified manually to remove instances of NO_AUTO_CREATE_USER.

  • In MySQL 8.0.11, these deprecated compatibility SQL modes were removed: DB2, MAXDB, MSSQL, MYSQL323, MYSQL40, ORACLE, POSTGRESQL, NO_FIELD_OPTIONS, NO_KEY_OPTIONS, NO_TABLE_OPTIONS. They can no longer be assigned to the sql_mode system variable or used as permitted values for the mysqldump --compatible option.

    Removal of MAXDB means that the TIMESTAMP data type for CREATE TABLE or ALTER TABLE is no longer treated as DATETIME.

    Replication from MySQL 5.7 to 8.0 of statements that refer to the removed SQL modes can cause replication failure. This includes replication of CREATE statements for stored programs (stored procedures and functions, triggers, and events) that are executed while the current sql_mode value includes any of the removed modes. Applications that use any of the removed modes should be revised to avoid them.

  • As of MySQL 8.0.3, spatial data types permit an SRID attribute, to explicitly indicate the spatial reference system (SRS) for values stored in the column. See Section 11.4.1, “Spatial Data Types”.

    A spatial column with an explicit SRID attribute is SRID-restricted: The column takes only values with that ID, and SPATIAL indexes on the column become subject to use by the optimizer. The optimizer ignores SPATIAL indexes on spatial columns with no SRID attribute. See Section 8.3.3, “SPATIAL Index Optimization”. If you want the optimizer to consider SPATIAL indexes on spatial columns that are not SRID-restricted, each such column should be modified:

    • Verify that all values within the column have the same SRID. To determine the SRIDs contained in a geometry column col_name, use the following query:

      SELECT DISTINCT ST_SRID(col_name) FROM tbl_name;

      If the query returns more than one row, the column contains a mix of SRIDs. In that case, modify its contents so all values have the same SRID.

    • Redefine the column to have an explicit SRID attribute.

    • Recreate the SPATIAL index.

  • Several spatial functions were removed in MySQL 8.0.0 due to a spatial function namespace change that implemented an ST_ prefix for functions that perform an exact operation, or an MBR prefix for functions that perform an operation based on minimum bounding rectangles. The use of removed spatial functions in generated column definitions could cause an upgrade failure. Before upgrading, run mysqlcheck --check-upgrade for removed spatial functions and replace any that you find with their ST_ or MBR named replacements. For a list of removed spatial functions, refer to Features Removed in MySQL 8.0.

  • The BACKUP_ADMIN privilege is automatically granted to users with the RELOAD privilege when performing an in-place upgrade to MySQL 8.0.3 or higher.

  • From MySQL 8.0.13, because of differences between row-based or mixed replication mode and statement-based replication mode in the way that temporary tables are handled, there are new restrictions on switching the binary logging format at runtime.

    • SET @@SESSION.binlog_format cannot be used if the session has any open temporary tables.

    • SET @@global.binlog_format and SET @@persist.binlog_format cannot be used if any replication channel has any open temporary tables. SET @@persist_only.binlog_format is allowed if replication channels have open temporary tables, because unlike PERSIST, PERSIST_ONLY does not modify the runtime global system variable value.

    • SET @@global.binlog_format and SET @@persist.binlog_format cannot be used if any replication channel applier is running. This is because the change only takes effect on a replication channel when its applier is restarted, at which time the replication channel might have open temporary tables. This behavior is more restrictive than before. SET @@persist_only.binlog_format is allowed if any replication channel applier is running.

InnoDB Changes

  • INFORMATION_SCHEMA views based on InnoDB system tables were replaced by internal system views on data dictionary tables. Affected InnoDB INFORMATION_SCHEMA views were renamed:

    Table 2.15 Renamed InnoDB Information Schema Views

    Old NameNew Name
    INNODB_SYS_COLUMNS INNODB_COLUMNS
    INNODB_SYS_DATAFILES INNODB_DATAFILES
    INNODB_SYS_FIELDS INNODB_FIELDS
    INNODB_SYS_FOREIGN INNODB_FOREIGN
    INNODB_SYS_FOREIGN_COLS INNODB_FOREIGN_COLS
    INNODB_SYS_INDEXES INNODB_INDEXES
    INNODB_SYS_TABLES INNODB_TABLES
    INNODB_SYS_TABLESPACES INNODB_TABLESPACES
    INNODB_SYS_TABLESTATS INNODB_TABLESTATS
    INNODB_SYS_VIRTUAL INNODB_VIRTUAL

    After upgrading to MySQL 8.0.3 or higher, update any scripts that reference previous InnoDB INFORMATION_SCHEMA view names.

  • The zlib library version bundled with MySQL was raised from version 1.2.3 to version 1.2.11.

    The zlib compressBound() function in zlib 1.2.11 returns a slightly higher estimate of the buffer size required to compress a given length of bytes than it did in zlib version 1.2.3. The compressBound() function is called by InnoDB functions that determine the maximum row size permitted when creating compressed InnoDB tables or inserting and updating rows in compressed InnoDB tables. As a result, CREATE TABLE ... ROW_FORMAT=COMPRESSED, INSERT, and UPDATE operations with row sizes very close to the maximum row size that were successful in earlier releases could now fail. To avoid this issue, test CREATE TABLE statements for compressed InnoDB tables with large rows on a MySQL 8.0 test instance prior to upgrading.

  • With the introduction of the --innodb-directories feature, the location of file-per-table and general tablespace files created with an absolute path or in a location outside of the data directory should be added to the innodb_directories argument value. Otherwise, InnoDB is not able to locate these files during recovery. To view tablespace file locations, query the INFORMATION_SCHEMA.FILES table: 

    SELECT TABLESPACE_NAME, FILE_NAME FROM INFORMATION_SCHEMA.FILES G

  • Undo logs can no longer reside in the system tablespace. In MySQL 8.0, undo logs reside in two undo tablespaces by default. For more information, see Section 15.6.3.4, “Undo Tablespaces”.

    When upgrading from MySQL 5.7 to MySQL 8.0, any undo tablespaces that exist in the MySQL 5.7 instance are removed and replaced by two new default undo tablespaces. Default undo tablespaces are created in the location defined by the innodb_undo_directory variable. If the innodb_undo_directory variable is undefined, undo tablespaces are created in the data directory. Upgrade from MySQL 5.7 to MySQL 8.0 requires a slow shutdown which ensures that undo tablespaces in the MySQL 5.7 instance are empty, permitting them to be removed safely.

    When upgrading to MySQL 8.0.14 or later from an earlier MySQL 8.0 release, undo tablespaces that exist in the pre-upgrade instance as a result of an innodb_undo_tablespaces setting greater than 2 are treated as user-defined undo tablespaces, which can be deactivated and dropped using ALTER UNDO TABLESPACE and DROP UNDO TABLESPACE syntax, respectively, after upgrading. Upgrade within the MySQL 8.0 release series may not always require a slow shutdown which means that existing undo tablespaces could contain undo logs. Therefore, existing undo tablespaces are not removed by the upgrade process.

  • Incompatible change: As of MySQL 8.0.17, the CREATE TABLESPACE ... ADD DATAFILE clause does not permit circular directory references. For example, the circular directory reference (/../) in the following statement is not permitted: 

    CREATE TABLESPACE ts1 ADD DATAFILE ts1.ibd 'any_directory/../ts1.ibd';

    An exception to the restriction exists on Linux, where a circular directory reference is permitted if the preceding directory is a symbolic link. For example, the data file path in the example above is permitted if any_directory is a symbolic link. (It is still permitted for data file paths to begin with '../'.)

    To avoid upgrade issues, remove any circular directory references from tablespace data file paths before upgrading to MySQL 8.0.17 or higher. To inspect tablespace paths, query the INFORMATION_SCHEMA.INNODB_DATAFILES table.

  • Due to a regression introduced in MySQL 8.0.14, in-place upgrade on a case sensitive file system from MySQL 5.7 or a MySQL 8.0 release prior to MySQL 8.0.14 to MySQL 8.0.16 failed for instances with partitioned tables and lower_case_table_names=1. The failure was caused by a case mismatch issue related to partitioned table file names. The fix that introduced the regression was reverted, which permits upgrades to MySQL 8.0.17 from MySQL 5.7 or MySQL 8.0 releases prior to MySQL 8.0.14 to function as normal. However, the regression is still present in the MySQL 8.0.14, 8.0.15, and 8.0.16 releases.

    In-place upgrade on a case sensitive file system from MySQL 8.0.14, 8.0.15, or 8.0.16 to MySQL 8.0.17 fails with the following error when starting the server after upgrading binaries or packages to MySQL 8.0.17 if partitioned tables are present and lower_case_table_names=1:

    Upgrading from server version version_number with 
partitioned tables and lower_case_table_names == 1 on a case sensitive file 
system may cause issues, and is therefore prohibited. To upgrade anyway, restart 
the new server version with the command line option 'upgrade=FORCE'. When 
upgrade is completed, please execute 'RENAME TABLE part_table_name 
TO new_table_name; RENAME TABLE new_table_name 
TO part_table_name;' for each of the partitioned tables. 
Please see the documentation for further information.

    If you encounter this error when upgrading to MySQL 8.0.17, perform the following workaround:

    1. Restart the server with --upgrade=force to force the upgrade operation to proceed.

    2. Identify partitioned table file names with lowercase partition name delimiters (#p# or #sp#):

      mysql> SELECT FILE_NAME FROM INFORMATION_SCHEMA.FILES WHERE FILE_NAME LIKE '%#p#%' OR FILE_NAME LIKE '%#sp#%';

    3. For each file identified, rename the associated table using a temporary name, then rename the table back to its original name.

      mysql> RENAME TABLE table_name TO temporary_table_name; 
mysql> RENAME TABLE temporary_table_name TO table_name;

    4. Verify that there are no partitioned table file names lowercase partition name delimiters (an empty result set should be returned).

      mysql> SELECT FILE_NAME FROM INFORMATION_SCHEMA.FILES WHERE FILE_NAME LIKE '%#p#%' OR FILE_NAME LIKE '%#sp#%';
Empty set (0.00 sec)

    5. Run ANALYZE TABLE on each renamed table to update the optimizer statistics in the mysql.innodb_index_stats and mysql.innodb_table_stats tables.

    Because of the regression still present in the MySQL 8.0.14, 8.0.15, and 8.0.16 releases, importing partitioned tables from MySQL 8.0.14, 8.0.15, or 8.0.16 to MySQL 8.0.17 is not supported on case sensitive file systems where lower_case_table_names=1. Attempting to do so results in a “Tablespace is missing for table” error.

  • MySQL uses delimiter strings when constructing tablespace names and file names for table partitions. A “#p#” delimiter string precedes partition names, and an “#sp#” delimiter string precedes subpartition names, as shown: 

    schema_name.table_name#p#partition_name#sp#subpartition_name
table_name#p#partition_name#sp#subpartition_name.ibd

    Historically, delimiter strings have been uppercase (#P# and #SP#) on case-sensitive file systems such as Linux, and lowercase (#p# and #sp#) on case-insensitive file systems such as Windows. As of MySQL 8.0.19, delimiter strings are lowercase on all file systems. This change prevents issues when migrating data directories between case-sensitive and case-insensitive file systems. Uppercase delimiter strings are no longer used.

    Additionally, partition tablespace names and file names generated based on user-specified partition or subpartition names, which can be specified in uppercase or lowercase, are now generated (and stored internally) in lowercase regardless of the lower_case_table_names setting to ensure case-insensitivity. For example, if a table partition is created with the name PART_1, the tablespace name and file name are generated in lowercase:

    schema_name.table_name#p#part_1
table_name#p#part_1.ibd

    During upgrade, MySQL checks and modifies if necessary:

    • Partition file names on disk and in the data dictionary to ensure lowercase delimiters and partition names.

    • Partition metadata in the data dictionary for related issues introduced by previous bug fixes.

    • InnoDB statistics data for related issues introduced by previous bug fixes.

    During tablespace import operations, partition tablespace file names on disk are checked and modified if necessary to ensure lowercase delimiters and partition names.

SQL Changes

  • Incompatible change: As of MySQL 8.0.13, the deprecated ASC or DESC qualifiers for GROUP BY clauses have been removed. Queries that previously relied on GROUP BY sorting may produce results that differ from previous MySQL versions. To produce a given sort order, provide an ORDER BY clause.

    Queries and stored program definitions from MySQL 8.0.12 or lower that use ASC or DESC qualifiers for GROUP BY clauses should be amended. Otherwise, upgrading to MySQL 8.0.13 or higher may fail, as may replicating to MySQL 8.0.13 or higher slave servers.

  • Some keywords may be reserved in MySQL 8.0 that were not reserved in MySQL 5.7. See Section 9.3, “Keywords and Reserved Words”. This can cause words previously used as identifiers to become illegal. To fix affected statements, use identifier quoting. See Section 9.2, “Schema Object Names”.

  • After upgrading, it is recommended that you test optimizer hints specified in application code to ensure that the hints are still required to achieve the desired optimization strategy. Optimizer enhancements can sometimes render certain optimizer hints unnecessary. In some cases, an unnecessary optimizer hint may even be counterproductive.

  • Incompatible change: In MySQL 5.7, specifying a FOREIGN KEY definition for an InnoDB table without a CONSTRAINT symbol clause, or specifying the CONSTRAINT keyword without a symbol, causes InnoDB to use a generated constraint name. That behavior changed in MySQL 8.0, with InnoDB using the FOREIGN KEY index_name value instead of a generated name. Because constraint names must be unique per schema (database), the change caused errors due to foreign key index names that were not unique per schema. To avoid such errors, the new constraint naming behavior has been reverted in MySQL 8.0.16, and InnoDB once again uses a generated constraint name.

    For consistency with InnoDB, NDB releases based on MySQL 8.0.16 or higher use a generated constraint name if the CONSTRAINT symbol clause is not specified, or the CONSTRAINT keyword is specified without a symbol. NDB releases based on MySQL 5.7 and earlier MySQL 8.0 releases used the FOREIGN KEY index_name value.

    The changes described above may introduce incompatibilities for applications that depend on the previous foreign key constraint naming behavior.

2.11.5 Preparing Your Installation for Upgrade

Before upgrading to the latest MySQL 8.0 release, ensure the upgrade readiness of your current MySQL 5.7 or MySQL 8.0 server instance by performing the preliminary checks described below. The upgrade process may fail otherwise.

The same checks and others can be performed using the MySQL Shell upgrade checker utility. For more information, see Upgrade Checker Utility.

Preliminary checks:

  1. The following issues must not be present:

    • There must be no tables that use obsolete data types or functions.

      In-place upgrade to MySQL 8.0 is not supported if tables contain old temporal columns in pre-5.6.4 format (TIME, DATETIME, and TIMESTAMP columns without support for fractional seconds precision). If your tables still use the old temporal column format, upgrade them using REPAIR TABLE before attempting an in-place upgrade to MySQL 8.0. For more information, see Server Changes.

    • There must be no orphan .frm files.

    • Triggers must not have a missing or empty definer or an invalid creation context (indicated by the character_set_client, collation_connection, Database Collation attributes displayed by SHOW TRIGGERS or the INFORMATION_SCHEMA TRIGGERS table). Any such triggers must be dumped and restored to fix the issue.

    To check for these issues, execute this command:

    mysqlcheck -u root -p --all-databases --check-upgrade

    If mysqlcheck reports any errors, correct the issues.

  2. There must be no partitioned tables that use a storage engine that does not have native partitioning support. To identify such tables, execute this query:

    SELECT TABLE_SCHEMA, TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE ENGINE NOT IN ('innodb', 'ndbcluster')
AND CREATE_OPTIONS LIKE '%partitioned%';

    Any table reported by the query must be altered to use InnoDB or be made nonpartitioned. To change a table storage engine to InnoDB, execute this statement:

    ALTER TABLE table_name ENGINE = INNODB;

    For information about converting MyISAM tables to InnoDB, see Section 15.6.1.5, “Converting Tables from MyISAM to InnoDB”.

    To make a partitioned table nonpartitioned, execute this statement:

    ALTER TABLE table_name REMOVE PARTITIONING;

  3. Some keywords may be reserved in MySQL 8.0 that were not reserved previously. See Section 9.3, “Keywords and Reserved Words”. This can cause words previously used as identifiers to become illegal. To fix affected statements, use identifier quoting. See Section 9.2, “Schema Object Names”.

  4. There must be no tables in the MySQL 5.7 mysql system database that have the same name as a table used by the MySQL 8.0 data dictionary. To identify tables with those names, execute this query:

    SELECT TABLE_SCHEMA, TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE LOWER(TABLE_SCHEMA) = 'mysql'
and LOWER(TABLE_NAME) IN
(
'catalogs',
'character_sets',
'check_constraints',
'collations',
'column_statistics',
'column_type_elements',
'columns',
'dd_properties',
'events',
'foreign_key_column_usage',
'foreign_keys',
'index_column_usage',
'index_partitions',
'index_stats',
'indexes',
'parameter_type_elements',
'parameters',
'resource_groups',
'routines',
'schemata',
'st_spatial_reference_systems',
'table_partition_values',
'table_partitions',
'table_stats',
'tables',
'tablespace_files',
'tablespaces',
'triggers',
'view_routine_usage',
'view_table_usage'
);

    Any tables reported by the query must be dropped or renamed (use RENAME TABLE). This may also entail changes to applications that use the affected tables.

  5. There must be no tables that have foreign key constraint names longer than 64 characters. Use this query to identify tables with constraint names that are too long:

    SELECT TABLE_SCHEMA, TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME IN
  (SELECT LEFT(SUBSTR(ID,INSTR(ID,'/')+1),
               INSTR(SUBSTR(ID,INSTR(ID,'/')+1),'_ibfk_')-1)
   FROM INFORMATION_SCHEMA.INNODB_SYS_FOREIGN
   WHERE LENGTH(SUBSTR(ID,INSTR(ID,'/')+1))>64);

    For a table with a constraint name that exceeds 64 characters, drop the constraint and add it back with constraint name that does not exceed 64 characters (use ALTER TABLE).

  6. The must be no obsolete SQL modes defined in your sql_mode system variable setting. Attempting to use an obsolete SQL mode will cause a startup failure on MySQL 8.0. Applications that use obsolete SQL modes should also be revised to avoid them. For information about SQL modes removed in MySQL 8.0, see Server Changes.

  7. There must be no views with explicitly defined columns names that exceed 64 characters (views with column names up to 255 characters were permitted in MySQL 5.7). To avoid upgrade errors, such views should be altered before upgrading. Currently, the only method of identify views with column names that exceed 64 characters is to inspect the view definition using SHOW CREATE VIEW. You can also inspect view definitions by querying the INFORMATION_SCHEMA.VIEWS table.

  8. There must be no tables or stored procedures with individual ENUM or SET column elements that exceed 255 characters or 1020 bytes in length. Prior to MySQL 8.0, the maximum combined length of ENUM or SET column elements was 64K. In MySQL 8.0, the maximum character length of an individual ENUM or SET column element is 255 characters, and the maximum byte length is 1020 bytes. (The 1020 byte limit supports multitibyte character sets). Before upgrading to MySQL 8.0, modify any ENUM or SET column elements that exceed the new limits. Failing to do so causes the upgrade to fail with an error.

  9. Before upgrading to MySQL 8.0.13 or higher, there must be no table partitions that reside in shared InnoDB tablespaces, which include the system tablespace and general tablespaces. Identify table partitions in shared tablespaces by querying INFORMATION_SCHEMA:

    If upgrading from MySQL 5.7, run this query:

    SELECT DISTINCT NAME, SPACE, SPACE_TYPE FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES 
  WHERE NAME LIKE '%#P#%' AND SPACE_TYPE NOT LIKE 'Single';

    If upgrading from an earlier MySQL 8.0 release, run this query:

    SELECT DISTINCT NAME, SPACE, SPACE_TYPE FROM INFORMATION_SCHEMA.INNODB_TABLES 
  WHERE NAME LIKE '%#P#%' AND SPACE_TYPE NOT LIKE 'Single';

    Move table partitions from shared tablespaces to file-per-table tablespaces using ALTER TABLE ... REORGANIZE PARTITION:

    ALTER TABLE table_name REORGANIZE PARTITION partition_name 
  INTO (partition_definition TABLESPACE=innodb_file_per_table);

  10. There must be no queries and stored program definitions from MySQL 8.0.12 or lower that use ASC or DESC qualifiers for GROUP BY clauses. Otherwise, upgrading to MySQL 8.0.13 or higher may fail, as may replicating to MySQL 8.0.13 or higher slave servers. For additional details, see SQL Changes.

  11. Your MySQL 5.7 installation must not use features that are not supported by MySQL 8.0. Any changes here are necessarily installation specific, but the following example illustrates the kind of thing to look for:

    Some server startup options and system variables have been removed in MySQL 8.0. See Features Removed in MySQL 8.0, and Section 1.5, “Server and Status Variables and Options Added, Deprecated, or Removed in MySQL 8.0”. If you use any of these, an upgrade requires configuration changes.

    Example: Because the data dictionary provides information about database objects, the server no longer checks directory names in the data directory to find databases. Consequently, the --ignore-db-dir option is extraneous and has been removed. To handle this, remove any instances of --ignore-db-dir from your startup configuration. In addition, remove or move the named data directory subdirectories before upgrading to MySQL 8.0. (Alternatively, let the 8.0 server add those directories to the data dictionary as databases, then remove each of those databases using DROP DATABASE.)

  12. If you intend to change the lower_case_table_names setting to 1 at upgrade time, ensure that schema and table names are lowercase before upgrading. Otherwise, a failure could occur due to a schema or table name lettercase mismatch. You can use the following queries to check for schema and table names containing uppercase characters:

    mysql> SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME != LOWER(TABLE_NAME) AND TABLE_TYPE = 'BASE TABLE';
mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME != LOWER(SCHEMA_NAME);

    As of MySQL 8.0.19, if lower_case_table_names=1, table and schema names are checked by the upgrade process to ensure that all characters are lowercase. If table or schema names are found to contain uppercase characters, the upgrade process fails with an error.

    Note

    Changing the lower_case_table_names setting at upgrade time is not recommended.

If upgrade to MySQL 8.0 fails due to any of the issues outlined above, the server reverts all changes to the data directory. In this case, remove all redo log files and restart the MySQL 5.7 server on the existing data directory to address the errors. The redo log files (ib_logfile*) reside in the MySQL data directory by default. After the errors are fixed, perform a slow shutdown (by setting innodb_fast_shutdown=0) before attempting the upgrade again.

2.11.11 Upgrading a Docker Installation of MySQL

To upgrade a Docker installation of MySQL, refer to Upgrading a MySQL Server Container.

2.11.12 Upgrade Troubleshooting

  • A schema mismatch in a MySQL 5.7 instance between the .frm file of a table and the InnoDB data dictionary can cause an upgrade to MySQL 8.0 to fail. Such mismatches may be due to .frm file corruption. To address this issue, dump and restore affected tables before attempting the upgrade again.

  • If problems occur, such as that the new mysqld server does not start, verify that you do not have an old my.cnf file from your previous installation. You can check this with the --print-defaults option (for example, mysqld --print-defaults). If this command displays anything other than the program name, you have an active my.cnf file that affects server or client operation.

  • If, after an upgrade, you experience problems with compiled client programs, such as Commands out of sync or unexpected core dumps, you probably have used old header or library files when compiling your programs. In this case, check the date for your mysql.h file and libmysqlclient.a library to verify that they are from the new MySQL distribution. If not, recompile your programs with the new headers and libraries. Recompilation might also be necessary for programs compiled against the shared client library if the library major version number has changed (for example, from libmysqlclient.so.20 to libmysqlclient.so.21).

  • If you have created a user-defined function (UDF) with a given name and upgrade MySQL to a version that implements a new built-in function with the same name, the UDF becomes inaccessible. To correct this, use DROP FUNCTION to drop the UDF, and then use CREATE FUNCTION to re-create the UDF with a different nonconflicting name. The same is true if the new version of MySQL implements a built-in function with the same name as an existing stored function. See Section 9.2.5, “Function Name Parsing and Resolution”, for the rules describing how the server interprets references to different kinds of functions.

  • If upgrade to MySQL 8.0 fails due to any of the issues outlined in Section 2.11.5, “Preparing Your Installation for Upgrade”, the server reverts all changes to the data directory. In this case, remove all redo log files and restart the MySQL 5.7 server on the existing data directory to address the errors. The redo log files (ib_logfile*) reside in the MySQL data directory by default. After the errors are fixed, perform a slow shutdown (by setting innodb_fast_shutdown=0) before attempting the upgrade again.

2.11.13 Rebuilding or Repairing Tables or Indexes

This section describes how to rebuild or repair tables or indexes, which may be necessitated by:

  • Changes to how MySQL handles data types or character sets. For example, an error in a collation might have been corrected, necessitating a table rebuild to update the indexes for character columns that use the collation.

  • Required table repairs or upgrades reported by CHECK TABLE, mysqlcheck, or mysql_upgrade.

Methods for rebuilding a table include:

Dump and Reload Method

If you are rebuilding tables because a different version of MySQL will not handle them after a binary (in-place) upgrade or downgrade, you must use the dump-and-reload method. Dump the tables before upgrading or downgrading using your original version of MySQL. Then reload the tables after upgrading or downgrading.

If you use the dump-and-reload method of rebuilding tables only for the purpose of rebuilding indexes, you can perform the dump either before or after upgrading or downgrading. Reloading still must be done afterward.

If you need to rebuild an InnoDB table because a CHECK TABLE operation indicates that a table upgrade is required, use mysqldump to create a dump file and mysql to reload the file. If the CHECK TABLE operation indicates that there is a corruption or causes InnoDB to fail, refer to Section 15.21.2, “Forcing InnoDB Recovery” for information about using the innodb_force_recovery option to restart InnoDB. To understand the type of problem that CHECK TABLE may be encountering, refer to the InnoDB notes in Section 13.7.3.2, “CHECK TABLE Statement”.

To rebuild a table by dumping and reloading it, use mysqldump to create a dump file and mysql to reload the file:

mysqldump db_name t1 > dump.sql
mysql db_name < dump.sql

To rebuild all the tables in a single database, specify the database name without any following table name:

mysqldump db_name > dump.sql
mysql db_name < dump.sql

To rebuild all tables in all databases, use the --all-databases option:

mysqldump --all-databases > dump.sql
mysql < dump.sql

ALTER TABLE Method

To rebuild a table with ALTER TABLE, use a “null” alteration; that is, an ALTER TABLE statement that “changes” the table to use the storage engine that it already has. For example, if t1 is an InnoDB table, use this statement: 

ALTER TABLE t1 ENGINE = InnoDB;

If you are not sure which storage engine to specify in the ALTER TABLE statement, use SHOW CREATE TABLE to display the table definition.

REPAIR TABLE Method

The REPAIR TABLE method is only applicable to MyISAM, ARCHIVE, and CSV tables.

You can use REPAIR TABLE if the table checking operation indicates that there is a corruption or that an upgrade is required. For example, to repair a MyISAM table, use this statement:

REPAIR TABLE t1;

mysqlcheck --repair provides command-line access to the REPAIR TABLE statement. This can be a more convenient means of repairing tables because you can use the --databases or --all-databases option to repair all tables in specific databases or all databases, respectively:

mysqlcheck --repair --databases db_name ...
mysqlcheck --repair --all-databases

2.11.14 Copying MySQL Databases to Another Machine

In cases where you need to transfer databases between different architectures, you can use mysqldump to create a file containing SQL statements. You can then transfer the file to the other machine and feed it as input to the mysql client.

Use mysqldump --help to see what options are available.

Note

If GTIDs are in use on the server where you create the dump (gtid_mode=ON), by default, mysqldump includes the contents of the gtid_executed set in the dump to transfer these to the new machine. The results of this can vary depending on the MySQL Server versions involved. Check the description for mysqldump's --set-gtid-purged option to find what happens with the versions you are using, and how to change the behavior if the outcome of the default behavior is not suitable for your situation.

The easiest (although not the fastest) way to move a database between two machines is to run the following commands on the machine on which the database is located:

mysqladmin -h 'other_hostname' create db_name
mysqldump db_name | mysql -h 'other_hostname' db_name

If you want to copy a database from a remote machine over a slow network, you can use these commands:

mysqladmin create db_name
mysqldump -h 'other_hostname' --compress db_name | mysql db_name

You can also store the dump in a file, transfer the file to the target machine, and then load the file into the database there. For example, you can dump a database to a compressed file on the source machine like this:

mysqldump --quick db_name | gzip > db_name.gz

Transfer the file containing the database contents to the target machine and run these commands there:

mysqladmin create db_name
gunzip < db_name.gz | mysql db_name

You can also use mysqldump and mysqlimport to transfer the database. For large tables, this is much faster than simply using mysqldump. In the following commands, DUMPDIR represents the full path name of the directory you use to store the output from mysqldump.

First, create the directory for the output files and dump the database:

mkdir DUMPDIR
mysqldump --tab=DUMPDIR db_name

Then transfer the files in the DUMPDIR directory to some corresponding directory on the target machine and load the files into MySQL there:

mysqladmin create db_name           # create database
cat DUMPDIR/*.sql | mysql db_name   # create tables in database
mysqlimport db_name DUMPDIR/*.txt   # load data into tables

Do not forget to copy the mysql database because that is where the grant tables are stored. You might have to run commands as the MySQL root user on the new machine until you have the mysql database in place.

After you import the mysql database on the new machine, execute mysqladmin flush-privileges so that the server reloads the grant table information.

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原文地址：https://www.cnblogs.com/jinzhenshui/p/12488777.html