MySQL 8.0.26 发布

• Previously, each event logged by MySQL Enterprise Audit included the SQL statement literal text. To provide an alternative (because it possible that statements contain sensitive information), the audit log filtering language now supports logging a statement’s digest rather than its literal text. For example, instead of logging this statement:
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  SELECT * FROM orders WHERE some_sensitive_column=1234567

  The audit log plugin can log this digest:

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  SELECT * FROM `orders` WHERE `some_sensitive_column` = ?

  This is similar to what is already logged for prepared statements, for which parameter markers appear rather than actual data values.

  To perform digest logging, use audit filter definitions that replace the statement literal text by its corresponding digest, as discussed in Replacement of Event Field Values.

  Because text replacement occurs at an early auditing stage (during filtering), the choice of whether to log statement literal text or digest values applies regardless of log format written later (that is, whether the audit log plugin produces XML or JSON output). (Bug #31482609)

• For MySQL Enterprise Audit, the new audit_log_format_unix_timestamp system variable enables inclusion of a time field in each audit record. The field value is an integer that represents the UNIX timestamp value indicating the date and time when the audit event was generated. The time field is supported only for JSON-format log files.
• For MySQL Enterprise Audit, the new audit_log_max_size system variable enables audit log file pruning based on combined log file size. To have an effect, audit_log_max_size requires that audit_log_rotate_on_size be greater than 0. If that is true, the pruning algorithm uses audit_log_max_size in conjunction with audit_log_prune_seconds, with nonzero values of audit_log_max_size taking precedence over nonzero values of audit_log_prune_seconds. For details, see Space Management of Audit Log Files.

• Previously, as part of the “hello” packet sent by the server to clients, the server sent the name of the server-side authentication plugin rather than the client-side plugin. The server now sends the client-side name, which is more appropriate for the client’s needs and may help to avoid extra protocol round trips.

• macOS: It is now possible to build MySQL for macOS 11 on ARM (that is, for Apple M1 systems). (Bug #32386050, Bug #102259)
• Building on openSUSE 15 and SLES 15 now requires GCC 9, found in packages gcc-9 and gcc9-c++.

  Building on SLES 12 now requires GCC 10, found in packages gcc-10 and gcc10-c++.

  It is also recommended to use the named GCC version when building third-party applications that are based on the libmysqlclient C API library. (Bug #32886268, Bug #32886439)

• Building on Ubuntu 18.04 (bionic) now requires GCC 8, found in packages gcc-8 and g++-8. It is also recommended to use GCC 8 when building third-party applications that are based on the libmysqlclient C API library. (Bug #32877062)
• It is now possible to build MySQL on Solaris using GCC 10, which becomes the default and recommended compiler. It is also recommended to use GCC 10 when building third-party applications that are based on the libmysqlclient C API library. (Bug #32552988)

• A new component service enables server components to set system variable values. For information about this service, see the MySQL Server Doxygen documentation, available at https://dev.mysql.com/doc/index-other.html (search for s_mysql_mysql_system_variable_update_string and mysql_system_variable_update_string_imp).

• The TLSv1 and TLSv1.1 connection protocols now are deprecated and support for them is subject to removal in a future MySQL version. (For background, refer to the IETF memo Deprecating TLSv1.0 and TLSv1.1.) It is recommended that connections be made using the more-secure TLSv1.2 and TLSv1.3 protocols. TLSv1.3 requires that both the MySQL server and the client application be compiled with OpenSSL 1.1.1 or higher.

  On the server side, this deprecation has the following effects:

  • If the tls_version or admin_tls_version system variable is assigned a value containing a deprecated TLS protocol, the server produces a warning for each deprecated protocol:
    • If the assignment occurs during server startup, the warning appears in the error log.
    • If the assignment occurs at runtime, the warning is added to the result of executing the ALTER INSTANCE RELOAD TLS statement.
  • If a client successfully connects using a deprecated TLS protocol, the server writes a warning to the error log.

  On the client side, the deprecation has no visible effect. Clients do not issue a warning if configured to permit a deprecated TLS protocol. This includes:

  • Client programs that support a --tls-version option for specifying TLS protocols for connections to the MySQL server.
  • Statements that enable replicas to specify TLS protocols for connections to the source server. (CHANGE REPLICATION SOURCE TO has a SOURCE_TLS_VERSION option and CHANGE MASTER TO has a MASTER_TLS_VERSION option.)
  • The group_replication_recovery_tls_version system variable that enables joining members to specify TLS protocols for distributed recovery connections.

  (Bug #32565996)

• The temptable_use_mmap variable is now deprecated and subject to removal in a future MySQL version.
• TLS support in MySQL has been moving toward a channel model using named sets of TLS parameters that apply to different securable ports or protocols. For example, to query the state of a particular TLS channel, use the Performance Schema tls_channel_status table:
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  mysql> SELECT VALUE FROM performance_schema.tls_channel_status
         WHERE CHANNEL = 'mysql_main' AND PROPERTY = 'Enabled';
  +-------+
  | VALUE |
  +-------+
  | Yes   |
  +-------+

  This makes monolithic parameters that apply to TLS support as a whole less applicable, so the following options and system variables are now deprecated and subject to removal in a future MySQL version:

  • The --ssl and --admin-ssl server options.
  • The have_ssl and have_openssl system variables.

  The --ssl and --admin-ssl options are enabled by default, so it is normally unnecessary to specify them. As an alternative to specifying those options in negated form, if it is desired to disable encrypted connections for the main or administrative interface, set the corresponding TLS version system variable to the empty value to indicate that no TLS versions are supported. For example, these lines in the server my.cnf file disable encrypted connections for both interfaces:

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  [mysqld]
  tls_version=''
  admin_tls_version=''

• Information written to the server error log for client timeouts now includes (if available) the timeout value, and client user and host. (Bug #31581289, Bug #100112)

• If the Event Scheduler is enabled, enabling the super_read_only system variable prevents it from updating event “last executed” timestamps in the events data dictionary table. This causes the Event Scheduler to stop the next time it tries to execute a scheduled event, after writing a message to the server error log.

  Previously, if enabling super_read_only caused the Event Scheduler to stop, then after subsequently disabling super_read_only, it was necessary to manually restart the Event Scheduler by enabling it again. As a convenience, the server now automatically restarts the Event Scheduler as needed when super_read_only is disabled. (Bug #31633859)

• In MySQL 8.0.23, MySQL Enterprise Firewall implemented group profiles that each can apply to multiple accounts, in addition to the previously implemented account profiles that each apply to a single account. See Using MySQL Enterprise Firewall.

  A group profile with a single member account is logically equivalent to an account profile for that account, so it is possible to administer the firewall using group profiles exclusively, rather than a mix of account and group profiles. For new firewall installations, that is accomplished by uniformly creating new profiles as group profiles and avoiding account profiles. For upgrades from firewall installations that already contain account profiles, MySQL Enterprise Firewall now includes a stored procedure named sp_migrate_firewall_user_to_group() for converting account profiles to group profiles.

  Due to the greater flexibility offered by group profiles, all aspects of the firewall related to account profiles are now deprecated and subject to removal in a future MySQL version:

  • INFORMATION_SCHEMA tables: MYSQL_FIREWALL_USERS, MYSQL_FIREWALL_WHITELIST
  • mysql system schema tables: firewall_users, firewall_whitelist
  • mysql system schema stored procedures: sp_reload_firewall_rules(), sp_set_firewall_mode()
  • Loadable functions: read_firewall_users(), read_firewall_whitelist(), set_firewall_mode()

  Additionally, if the server detects account profiles at startup, it writes a warning for every successfully loaded account profile.

  For information about converting account profiles to group profiles (which you should do at your earliest convenience), see Migrating Account Profiles to Group Profiles.

• Binary packages that include curl rather than linking to the system curl library have been upgraded to use curl 7.77.0. (Bug #33077562)
• For Ubuntu packages, the AppArmor profile for mysqld was too restrictive regarding PID and socket file names and failed for servers not using the exact names in the profile. Now the profile applies to the directories in which the files live, enabling it to apply for different file names, and multiple servers. (Bug #32857611)
• The dh-systemd package has been removed from Ubuntu 21.04, so the dependency on it has been removed from MySQL packages built for that distribution. (Bug #32688072)
• For Debian packages, an EnvironmentFile directive was added to enable the systemd service to read environmental variables from the /etc/default/mysql file if it is present. (Bug #32082863, Bug #101363)
• Debian packages now use /run rather than /var/run for path names. (Bug #31955638)
• The bundled lz4 library was upgraded to version 1.9.3. (Bug #29747853)
• For Debian packages, the update-alternatives priority of the MySQL configuration file was increased to ensure it replaces an existing file from a previously installed distribution. (Bug #29606955)

• Linux: MySQL Enterprise Edition now supports an authentication method that enables users to authenticate to MySQL Server using Kerberos, provided that appropriate Kerberos tickets are available or can be obtained. For details, see Kerberos Pluggable Authentication.

  This authentication method uses a pair of plugins, authentication_kerberos on the server side and authentication_kerberos_client on the client side. It is available only on MySQL server and client hosts running Linux, but can access Kerberos services running on non-Linux hosts.

• Setting the session value of the innodb_strict_mode system variable is now a restricted operation and the session user must have privileges sufficient to set restricted session variables.

  For information about the privileges required to set restricted session variables, see System Variable Privileges. (Bug #32944980)

• The ST_Buffer() function now permits the geometry argument to have a geographic spatial reference system (SRS), if the geometry is a point value. Previously, ST_Buffer() supported only geometry arguments in a Cartesian SRS. The ST_Difference() and ST_Union() functions now permit the geometry arguments to have a geographic SRS. Previously, ST_Difference() and ST_Union() supported only geometry arguments in a Cartesian SRS. See Spatial Operator Functions.

• When the X DevAPI Session.run_sql() method was used to execute a query that returned multiple results, due to a caching issue, the result.columns property was not updated to reflect the columns present in the active result, although the result.column_names property was. (Bug #32887586)
• During an upgrade process, X Plugin logged a message stating that it was ready for connections once the TCP port and UNIX socket had been allocated. However, connections could not actually be accepted until after the upgrade process was complete. The message is now issued only after the upgrade has finished. (Bug #32814997)

• Incompatible Change: From MySQL 8.0.26, new aliases or replacement names are provided for most remaining identifiers that contain the terms “master”, which is changed to “source”; “slave”, which is changed to “replica”; and “mts” (for “multithreaded slave”), which is changed to “mta” (for “multithreaded applier”). Help text is also changed where applicable to use the new names.

  The following name replacements are visible in the Performance Schema tables, the process list, and the replica status information. These changes are incompatible with earlier releases. Monitoring tools that work with these instrumentation names might be impacted:

  • Instrumented locks (mutexes), visible in the mutex_instances and events_waits_* Performance Schema tables with the prefix wait/synch/mutex/
  • Read/write locks, visible in the rwlock_instances and events_waits_* Performance Schema tables with the prefix wait/synch/rwlock/
  • Instrumented condition variables, visible in the cond_instances and events_waits_* Performance Schema tables with the prefix wait/synch/cond/
  • Instrumented memory allocations, visible in the memory_summary_* Performance Schema tables with the prefix memory/sql/
  • Thread names, visible in the threads Performance Schema table with the prefix thread/sql/
  • Thread stages, visible in the events_stages_* Performance Schema tables with the prefix stage/sql/, and without the prefix in the threads and processlist Performance Schema tables, the output from the SHOW PROCESSLIST statement, the Information Schema processlist table, and the slow query log
  • Thread commands, visible in the events_statements_history* and events_statements_summary_*_by_event_name Performance Schema tables with the prefix statement/com/, and without the prefix in the threads and processlist Performance Schema tables, the output from the SHOW PROCESSLIST statement, the Information Schema processlist table, and the output from the SHOW REPLICA STATUS statement

  If the incompatible changes do have an impact for you, you can set the new system variable terminology_use_previous to BEFORE_8_0_26 to make MySQL Server use the old versions of the names for the objects specified in the previous list. This enables monitoring tools that rely on the old names to continue working until they can be updated to use the new names. The system variable can be set with session scope to support individual functions, or global scope to be a default for all new sessions. When global scope is used, the slow query log contains the old versions of the names.

  For semisynchronous replication, you can choose whether to use the new or the old versions of the system variables and status variables. New versions of the plugins that implement semisynchronous replication, one for the source server and one for the replica, are supplied that replace the terms master and slave with source and replica, and you can install these versions instead of the old ones:

  • The rpl_semi_sync_master plugin (semisync_master.so library) for the source has a new version rpl_semi_sync_source (semisync_source.so library)
  • The rpl_semi_sync_slave plugin (semisync_slave.so library) for the replica has a new version rpl_semi_sync_replica (semisync_replica.so library)

  You cannot have both the new and the old version of the relevant plugin installed on an instance. If you use the new version of the plugins, the new system variables and status variables are available but the old ones are not. If you use the old version of the plugins, the old system variables and status variables are available but the new ones are not.

  The following internal-use items are converted to use the new terms but are not externalized to users or monitoring tools, and MySQL Server handles any necessary resolution internally:

  • C++ filenames in source code
  • Header guards in C++ files
  • Debug symbols
  • User variables passed in the replication protocol handshake by the replica when it connects to a replication source server (the replica sets both the old and the new name)

  The following categories of identifiers have a new alias, and a deprecation warning is issued when the old name is used, although the old name continues to work. Both names are available in Performance Schema tables and status displays, and no deprecation warning is issued when reading these. The new aliases are not affected by the new system variable terminology_use_previous, and can still be used when it is set:

  • System variables that contain the terms “master”, “slave”, or “mts”, with the exception of some that have already been deprecated or are scheduled for deprecation, and those defined by NDB. If these system variables are persisted using a SET PERSIST statement, both the old and the new name are persisted, regardless of which was specified in the statement. With a RESET PERSIST statement, both are reset.
  • Status variables that contain the terms “master”, “slave”, or “mts”, with the exception of those defined by NDB.
  • Command-line options for mysqld that contain the terms “master”, “slave”, or “mts”, with the exception of some that have already been deprecated or are scheduled for deprecation, and those defined by NDB.
  • Command-line options for mysqladmin that contain the terms “master”, “slave”, or “mts”.
  • Command-line options for mysqlbinlog that contain the terms “master”, “slave”, or “mts”.
  • Command-line options for mysqldump that contain the terms “master”, “slave”, or “mts”.
  • An SQL function that contains the term “master”.

  The complete list of identifiers with new aliases (or in the case of semisynchronous replication, replacements) is as follows:

  • System variables:
    • master_verify_checksum now has the alias source_verify_checksum
    • sync_master_info now has the alias sync_source_info
    • init_slave now has the alias init_replica
    • rpl_stop_slave_timeout now has the alias rpl_stop_replica_timeout
    • log_slow_slave_statements now has the alias log_slow_replica_statements
    • slave_max_allowed_packet now has the alias replica_max_allowed_packet
    • slave_compressed_protocol now has the alias replica_compressed_protocol
    • slave_exec_mode now has the alias replica_exec_mode
    • slave_type_conversions now has the alias replica_type_conversions
    • slave_sql_verify_checksum now has the alias replica_sql_verify_checksum
    • slave_parallel_type now has the alias replica_parallel_type
    • slave_preserve_commit_order now has the alias replica_preserve_commit_order
    • log_slave_updates now has the alias log_replica_updates
    • slave_allow_batching now has the alias replica_allow_batching
    • slave_load_tmpdir now has the alias replica_load_tmpdir
    • slave_net_timeout now has the alias replica_net_timeout
    • sql_slave_skip_counter now has the alias sql_replica_skip_counter
    • slave_skip_errors now has the alias replica_skip_errors
    • slave_checkpoint_period now has the alias replica_checkpoint_period
    • slave_checkpoint_group now has the alias replica_checkpoint_group
    • slave_transaction_retries now has the alias replica_transaction_retries
    • slave_parallel_workers now has the alias replica_parallel_workers
    • slave_pending_jobs_size_max now has the alias replica_pending_jobs_size_max
    • pseudo_slave_mode now has the alias pseudo_replica_mode
    • skip_slave_start now has the alias skip_replica_start
  • If the new rpl_semi_sync_source and rpl_semi_sync_replica plugins are used for semisynchronous replication:
    • rpl_semi_sync_slave_enabled is replaced by rpl_semi_sync_replica_enabled
    • rpl_semi_sync_slave_trace_level is replaced by rpl_semi_sync_replica_trace_level
    • rpl_semi_sync_master_wait_for_slave_count is replaced by rpl_semi_sync_source_wait_for_replica_count
    • rpl_semi_sync_master_enabled is replaced by rpl_semi_sync_source_enabled
    • rpl_semi_sync_master_timeout is replaced by rpl_semi_sync_source_timeout
    • rpl_semi_sync_master_trace_level is replaced by rpl_semi_sync_source_trace_level
    • rpl_semi_sync_master_wait_point is replaced by rpl_semi_sync_source_wait_point
  • The following system variables are not changed:
    • ndb_slave_conflict_role (NDB system variables are not changed)
    • binlog_rotate_encryption_master_key_at_startup (“master key” is an accepted term)
    • slave_rows_search_algorithms (This system variable is already deprecated)
    • master_info_repository (This system variable is already deprecated)
  • Status variables:
    • Slave_open_temp_tables now has the alias Replica_open_temp_tables
    • Slave_rows_last_search_algorithm_used now has the alias Replica_rows_last_search_algorithm_used
  • If the new rpl_semi_sync_source and rpl_semi_sync_replica plugins are used for semisynchronous replication:
    • Rpl_semi_sync_slave_status is replaced by Rpl_semi_sync_replica_status
    • Rpl_semi_sync_master_status is replaced by Rpl_semi_sync_source_status
    • Rpl_semi_sync_master_clients is replaced by Rpl_semi_sync_source_clients
    • Rpl_semi_sync_master_yes_tx is replaced by Rpl_semi_sync_source_yes_tx
    • Rpl_semi_sync_master_no_tx is replaced by Rpl_semi_sync_source_no_tx
    • Rpl_semi_sync_master_wait_sessions is replaced by Rpl_semi_sync_source_wait_sessions
    • Rpl_semi_sync_master_no_times is replaced by Rpl_semi_sync_source_no_times
    • Rpl_semi_sync_master_timefunc_failures is replaced by Rpl_semi_sync_source_timefunc_failures
    • Rpl_semi_sync_master_wait_pos_backtraverse is replaced by Rpl_semi_sync_source_wait_pos_backtraverse
    • Rpl_semi_sync_master_tx_wait_time is replaced by Rpl_semi_sync_source_tx_wait_time
    • Rpl_semi_sync_master_tx_waits is replaced by Rpl_semi_sync_source_tx_waits
    • Rpl_semi_sync_master_tx_avg_wait_time is replaced by Rpl_semi_sync_source_tx_avg_wait_time
    • Rpl_semi_sync_master_net_wait_time is replaced by Rpl_semi_sync_source_net_wait_time
    • Rpl_semi_sync_master_net_waits is replaced by Rpl_semi_sync_source_net_waits
    • Rpl_semi_sync_master_net_avg_wait_time is replaced by Rpl_semi_sync_source_net_avg_wait_time
  • NDB-related status variables are not changed.
  • For mysqld, the command-line versions of all the aliased and replaced system variables in the lists above have equivalent command-line aliases or replacements, plus the following command-line option that is not a system variable:
    • show-slave-auth-info has the alias show-replica-auth-info
  • The following command-line options are not changed:
    • abort-slave-event-count (This command-line option is scheduled for deprecation)
    • disconnect-slave-event-count (This command-line option is scheduled for deprecation)
    • master-info-file (This command-line option is already deprecated)
    • master-retry-count (This command-line option is already deprecated)
  • For mysqladmin, the option start-slave now has the alias start-replica, and the option stop-slave now has the alias stop-replica.
  • For mysqlbinlog, the option read-from-remote-master now has the alias read-from-remote-source.
  • For mysqldump, the following command-line options have new aliases:
    • apply-slave-statements now has the alias apply-replica-statements
    • delete-master-logs now has the alias delete-source-logs
    • dump-slave now has the alias dump-replica
    • include-master-host-port now has the alias include-source-host-port
    • master-data now has the alias source-data
  • The built-in SQL function MASTER_POS_WAIT has a new alias SOURCE_POS_WAIT.
• InnoDB: The new innodb_segment_reserve_factor system variable permits configuring the percentage of tablespace file segment pages that are reserved as empty pages. For more information, see Configuring the Percentage of Reserved File Segment Pages.

  Thanks to Facebook for the contribution. (Bug #32312743, Bug #102044)

• The URL for downloading Boost was updated. Thanks to Marcelo Altmann for the contribution. (Bug #32856104, Bug #103611)
• These statements now report utf8mb3 rather than utf8 when writing character set names: EXPLAIN, SHOW CREATE PROCEDURE, SHOW CREATE EVENT.

  Stored program definitions retrieved from the data dictionary now report utf8mb3 rather than utf8 in character set references. This affects any output produced from those definitions, such as SHOW CREATE statements.

  This error message now reports utf8mb3 rather than utf8 when writing character set names: ER_INVALID_CHARACTER_STRING. (Bug #32233614, Bug #32392077, Bug #32392209, Bug #32428538, Bug #32428598)

• For Group Replication, a group in single-primary mode can now be configured to stay in super read-only mode, so that it only accepts replicated transactions and does not accept any direct writes from clients. This setup means that when a group’s purpose is to provide a secondary backup to another group for disaster tolerance, you can ensure that the secondary group remains synchronized with the first. You can configure the group to remain in super read-only mode when a new primary is elected, by disabling the action that normally takes place to remove that mode on the primary.

  Administrators can configure a group in this way using the new Group Replication functions group_replication_enable_member_action and group_replication_disable_member_action, which can enable and disable actions for members of a group to take in specified situations. The functions can also be used on servers that are not part of a group, as long as the Group Replication plugin is installed. Member actions are configured on the primary and propagated to other group members and joining members using group messages. Another function group_replication_reset_member_actions is available to reset the member actions configuration to the default setting for all member actions.

• The system variable transaction_write_set_extraction is now deprecated, and a warning message is issued if you attempt to set it or read its value. The system variable will be removed in a future MySQL version. This system variable was used on a replication source server that has multithreaded replicas, to specify the algorithm used to hash the writes extracted for a transaction’s write set. The XXHASH64 algorithm, which is the default in MySQL 8.0 and is required for Group Replication, is selected when the system variable is not used.
• You can now select an alternative UUID to form part of the GTIDs that are used when Group Replication’s internally generated transactions for view changes (View_change_log_event) are written to the binary log. The new Group Replication system variable group_replication_view_change_uuid specifies a UUID that is used instead of the group name (the value of the group_replication_group_name system variable). The alternative UUID makes it easier to distinguish view change events from transactions received by the group from clients. This can be useful if your setup allows for failover between groups, and you need to identify and discard transactions that were specific to the backup group. Note that all members of the group must have the same alternative UUID specified, so groups set up in this way cannot include members at releases below MySQL 8.0.26.
• On platforms that support fdatasync() system calls, the new innodb_use_fdatasync variable permits using fdatasync() instead of fsync() for operating system flushes. An fdatasync() system call does not flush changes to file metadata unless required for subsequent data retrieval, providing a potential performance benefit. The innodb_use_fdatasync variable can be set dynamically using a SET statement.

• Incompatible Change: Within trigger bodies, INSERT or UPDATE statements containing a SET clause that used OLD or NEW values as assignment targets could raise an assertion or lead to a server exit. Such assignments are no longer permitted. (Bug #32803211)
• Performance: Internal functions used to copy values between columns have been improved such that computations not necessary when the values are of similar types are no longer performed. Queries using temporary tables should be noticeably faster with this enhancement. Our internal testing has shown such queries being executed up to 11% faster than previously; as always, your results may differ from these depending on environment, configuration, and other factors. (Bug #32742537)
• InnoDB: To reduce the number of unnecessary warning messages in the error log, instances of the fil_space_acquire() function in the InnoDB sources were replaced by the fil_space_acquire_silent() function where possible. (Bug #32944543)
• InnoDB: The TRX_FORCE_ROLLBACK_ASYNC flag in the InnoDB sources, which indicates whether a transaction was rolled back asynchronously or by the owning thread, was found to be redundant and has been removed. (Bug #32912595)
• InnoDB: Use of the ut_delete symbol instead of the UT_DELETE macro in the InnoDB sources caused a failure in builds that disable Performance Schema memory tracing (-DDISABLE_PSI_MEMORY=ON). (Bug #32910699)
• InnoDB: Dictionary system mutex_enter and mutex_exit calls in the InnoDB sources were renamed to dict_sys_mutex_enter() and dict_sys_mutex_exit(), respectively. (Bug #32907980)
• InnoDB: Legacy UNIV_INLINE and UNIV_MATERIALIZE artifacts were removed from InnoDB sources. UNIV_HOTBACKUP was added to method declarations in some header files. (Bug #32894165)
• InnoDB: The lock_sys sharded rw_lock index used random index values generated by the ut_rnd_interval() function, which was not optimal for low-concurrency workloads. (Bug #32880577)
• InnoDB: A string value setting for the innodb_redo_log_encrypt variable was not handled properly. (Bug #32851525)
• InnoDB: Read-write transaction set (trx_sys->rw_trx_set) shards, each with a dedicated mutex, were introduced to alleviate transaction system mutex (trx_sys->mutex) contention caused by transaction set insertions and removals. Related enhancements include moving transaction set modifiers to less critical locations, eliminating heap allocation inside of the TrxUndoRsegs constructor, converting transaction state (trx->state) and transaction start time (trx->start_time) fields to std::atomic fields, and new assertion code to validate threads that operate on transactions. (Bug #32832196)
• InnoDB: Record buffer logic for the InnoDB memcached GET command was revised. (Bug #32828352)
• InnoDB: The ut_list base member in the InnoDB sources now locates list nodes using the element portion of the list type rather than storing a member pointer in the base node of a list at runtime, which waisted resources. The patch also includes other ut_list related code improvements. (Bug #32820458)
• InnoDB: A deadlock between a user thread and purge thread involving a undo log page and rollback segment page occurred after an undo tablespace truncate operation was initiated. The deadlock caused a long semaphore wait and an eventual failure. (Bug #32800020)
• InnoDB: Type-safe enhancements for PSI_memory_key identifiers were introduced. PSI_memory_key identifiers are used by Performance Schema for instrumentation of memory operations. With this enhancement, ut::aligned_name library functions are able to report type errors at compile time. (Bug #32797838)
• InnoDB: The buf_get_LRU_mutex() function was optimized to avoid acquiring the LRU mutex unnecessarily when flushing from the flush list. (Bug #32797451, Bug #103391)
• InnoDB: In debug builds, an access to Fil_shard::m_deleted_spaces (deleted tablespaces vector) was not protected by the Fil_shard mutex, causing a failure. (Bug #32792816)
• InnoDB: Enabling innodb_dedicated_server on a machine with 2GB of RAM resulted in a single redo log file being created, causing a startup failure. The innodb_dedicated_server automated configuration logic was revised to ensure that a minimum of two log files are created.

  Thanks to Adam Cable for the contribution. (Bug #32788772, Bug #103372)

• InnoDB: A failure occurred when truncating a partitioned table after an operation that added too many columns to the table, exceeding the column limit. The number of columns added is now evaluated before an ADD COLUMN operation is permitted. (Bug #32788564, Bug #103363)
• InnoDB: On platforms that support punch hole where the disk is near full, creating a tablespace with a large AUTOEXTEND_SIZE setting could lead to a no space on device failure and a subsequent InnoDB recovery failures. (Bug #32771235)
• InnoDB: The list of table locks requested by a transaction (trx->lock.table_locks), which is a subset of the transaction lock list (trx->lock.trx_locks), was removed. Table locks requested by a transaction are now are now listed at the beginning of the transaction lock list instead. (Bug #32762881)
• InnoDB: A failure occurred during recovery with the disk being near full, leaving the data in an inconsistent state. The failure occurred in the fil_tablespace_redo_extend() function, which is used to redo a tablespace extension operation. (Bug #32749974, Bug #32748733)
• InnoDB: After relocating a file-per-table tablespace offline and making the new location known to InnoDB using the innodb_directories option, an ALTER TABLE operation that used the COPY algorithm failed with a storage engine error. The failure was due to a renaming check, which searched the data directory instead of the new directory location. (Bug #32721533)
• InnoDB: ut_allocator() compliance issues with the C++ standard template library (STL) were addressed. (Bug #32715698)
• InnoDB: Instances of ut_allocator::allocate() instantiated by std::vector in the InnoDB sources failed to trace memory allocations and deallocations performed implicitly by std::vector. The same issue was found for other C++ standard template library (STL) and STL-like data-structures. (Bug #32715688)
• InnoDB: The ut_allocator::construct() interface in the InnoDB sources, which is a custom interface implemented in a pre-C++11 style, caused unnecessary overhead. The interface was not necessary and has been removed. (Bug #32715381)
• InnoDB: The ut_list length member variable in the InnoDB sources was replaced by an atomic field to permit lock free access without undefined behavior. The default ut_list constructor was replaced by a new constructor that performs all list initialization. (Bug #32715371)
• InnoDB: The ut_allocator() out of memory reporting mechanism in the InnoDB sources was not reliable and has been removed. (Bug #32715359)
• InnoDB: Implicit handling of Performance Schema metadata was implemented for ut_allocator::allocate_large() and ut_allocator::deallocate_large() functions in the InnoDB sources. This modification aligns Performance Schema metadata handling with that of similar allocation functions. (Bug #32714144)
• InnoDB: Stalls were caused by concurrent SELECT COUNT(*) queries where the number of parallel read threads exceeded the number of machine cores. A patch for this issue was provided for Windows builds in MySQL 8.0.24. The MySQL 8.0.26 patch addresses the same issue on other affected platforms. (Bug #32678019)

  References: See also: Bug #32224707.

• InnoDB: To avoid costly calls to the rec_get_offsets() function, which determines the offsets for each field in a record, caching of offsets is extended to indexes that meet certain requirements such as having a fixed length, no virtual columns, instant columns, and so on. (Bug #32673649)
• InnoDB: When starting the server with a data directory that was restored by MySQL Enterprise Backup, the doublewrite buffer (controlled by the innodb_doublewrite variable) remained disabled until the next server restart. (Bug #32642866)
• InnoDB: “Too many open files” errors were encountered when creating a large number of tables. (Bug #32634620)

  References: This issue is a regression of: Bug #32541241.

• InnoDB: InnoDB recovery was unable to proceed due to a page tracking system recovery failure, which should have been non-blocking. (Bug #32630875)
• InnoDB: An integer underflow issue was addressed in the InnoDB mecached plugin sources. (Bug #32620378, Bug #32620398)
• InnoDB: When a transaction started waiting for lock, the InnoDB lock system provided information to the server about the transaction currently holding the lock but failed to inform the server after releasing the lock and grating it to another waiting transaction. As a result, the replication applier thread coordinator was unable to detect potential deadlocks in the intended transaction commit order that could occur if the third transaction in this scenario committed after the initial waiting transaction. (Bug #32618301)
• InnoDB: When inserting a record into a unique secondary index, the index record locks taken to prevent concurrent transactions from inserting a conflicting record into the affected range included an unnecessary gap lock on the first record after the range. (Bug #32617942)
• InnoDB: InnoDB code that creates dynamically allocated over-aligned types was replaced by ut::aligned_name library functions. (Bug #32601599)
• InnoDB: Memory allocation functions belonging to the API that handles dynamic storage of over-aligned types (ut::aligned_name library functions) were extended to support memory tracing using Performance Schema. The HAVE_PSI_MEMORY_INTERFACE source configuration option enables the memory tracing module.

  An aligned_zalloc() library function, which provides support for zero-initialized memory allocations, was added to the API. (Bug #32600981)

  References: See also: Bug #32601599, Bug #32246061, Bug #32246200.

• InnoDB: Sampling of InnoDB data for the purpose of generating histogram statistics is now supported with all transaction isolation levels supported by InnoDB. Previously, sampling was performed using only the READ UNCOMMITTED isolation level. (Bug #32555575)
• InnoDB: An index with a key prefix length greater than 767 bytes was permitted on a table defined with the REDUNDANT row format, exceeding the index key prefix length limit for that row format. The ALTER TABLE operation that added the index validated the index key prefix length for the row format defined by the innodb_default_row_format variable instead of the actual row format of the table. The fix ensures that index key prefix length is validated for the correct row format. (Bug #32507117, Bug #102597)
• InnoDB: Adaptive hash index latches did not provide meaningful latch location information. (Bug #32477773)
• InnoDB: A dependency related to redo and undo log encryption at server initialization time was removed. (Bug #32476724)
• InnoDB: An online buffer pool resizing operation freed the previous buffer pool page hash, conflicting with a concurrent buffer pool lookup that required the previous page hash. (Bug #32460315)
• InnoDB: When using the TempTable storage engine (internal_tmp_mem_storage_engine=TempTable), more than 255 aggregate functions in a SELECT list caused errors due to overflow of an internal variable that stores indexed column field positions. (Bug #32458104, Bug #102468)
• InnoDB: A workload stalled while executing a undo tablespace truncation operation on an instance with a large buffer pool. The function that truncates marked undo tablespaces now takes a shared latch instead of an exclusive latch, and the shared latch is taken for a shorter period of time. (Bug #32353863, Bug #102143)
• InnoDB: A programming interface was added for handling dynamic storage of over-aligned types. (Bug #32246200, Bug #32246061)
• InnoDB: Under certain circumstances, a failure during InnoDB recovery could have caused a loss of committed changes. Checkpoints permitted during recovery did not handle page flushing, flush list maintenance, or persisting changes to the data dictionary table buffer as necessary for a proper checkpoint operations. Checkpoints and advancing the checkpoint LSN are therefore no longer permitted until redo log recovery is complete and data dictionary dynamic metadata (srv_dict_metadata) is transferred to data dictionary table (dict_table_t) objects. Should the redo log run out of space during recovery or after recovery (but before data dictionary dynamic metadata is transferred to data dictionary table objects) as a result of this change, an innodb_force_recovery restart may be required, starting with at least the SRV_FORCE_NO_IBUF_MERGE setting or, in case that fails, the SRV_FORCE_NO_LOG_REDO setting. If an innodb_force_recovery restart fails in this scenario, recovery from backup may be necessary. (Bug #32200595)
• InnoDB: Rollback segments are now initialized in parallel during startup. Previously, rollback segments were initialized serially. (Bug #32170127, Bug #101658)
• InnoDB: A failure occurred during testing of innodb_log_writer_threads variable configuration. The failure was caused by a race condition. (Bug #32129814)

  References: This issue is a regression of: Bug #30088404.

• InnoDB: A race condition occurred between a purge thread that was truncating an undo tablespace and a server thread that queried the INFORMATION_SCHEMA.FILES table. As a result, the truncated undo tablespace did not appear in the INFORMATION_SCHEMA.FILES table when queried, which in turn caused a MySQL Enterprise Backup failure due to a dependency on the INFORMATION_SCHEMA.FILES table for undo tablespace file locations. (Bug #32104924, Bug #32654667)
• InnoDB: When DML operations are concentrated on a single table, purge work was performed by a single purge thread, which could result in slowed purge operations, increased purge lag, and increased tablespace file size if DML operations involve large object values. To address this issue, purge work is now automatically redistributed among available purge threads when the purge lag exceeds the innodb_max_purge_lag setting. (Bug #32089028)
• InnoDB: The function that populates the INFORMATION_SCHEMA.INNODB_TABLESPACES table accessed the space for a file and performed an unprotected stat() operation and retrieval of file size information. (Bug #32025344)
• InnoDB: Code related to the trx_t::is_recovered flag in the InnoDB sources was revised to address various complexity and correctness issues. One of the issues addressed caused an XA transaction to be described incorrectly as “recovered”, which occurred when a client session disconnected from an XA transaction after XA PREPARE. (Bug #31870582)
• InnoDB: TempTable debug assertion code for an Indexed_cells member function (cell_from_mysql_buf_index_read()) did not account for non-nullable columns with zero length. (Bug #31091089)
• InnoDB: Using the InnoDB memcached plugin, attempting to retrieve multiple values in a single get command returned an incorrect value. (Bug #29675958, Bug #95032)
• InnoDB: The trx_sys_t::serialisation_mutex was introduced to reduce contention on the on the trx_sys_t::mutex. The new mutex protects the trx_sys_t::serialisation_list when a transaction number is assigned, which was previously protected by the trx_sys_t::mutex.

  Thanks to Zhai Weixiang for the contribution. (Bug #27933068, Bug #90643)

• Partitioning: When a table was partitioned by TIMESTAMP and a timestamp literal with a time zone offset was used in the WHERE clause of a SELECT statement, it was possible for a partition to be omitted from the result set.

  When a time zone offset is specified in a timestamp literal, it is expected to be converted to a timestamp without a time zone offset, and then compared against a timestamp column, but this was not done properly in all cases, with the result that a partition could be pruned while selecting the partitions to be scanned for the query.

  We fix this by making sure that a timestamp with a time zone offset is always converted as described before comparing with values from the column. (Bug #101530, Bug #32134145)

• Replication: When the SOURCE_CONNECTION_AUTO_FAILOVER=1 option was set on the CHANGE REPLICATION SOURCE TO statement for a replication channel, a STOP REPLICA IO_THREAD statement did not stop the monitor thread that monitors for connection failures on the channel, and could incorrectly stop the applier thread. (Bug #32892977)
• Replication: When the system variable replication_optimize_for_static_plugin_config was set, the plugins for Group Replication and semi-synchronous replication could not be uninstalled cleanly on server shutdown. (Bug #32798287)
• Replication: In Group Replication’s single-primary mode, unnecessary copies of the transaction data were created during data serialization. This is now done in a single step to reduce the memory footprint. (Bug #32781945)
• Replication: A deadlock could occur when START GROUP_REPLICATION and STOP GROUP_REPLICATION statements were issued at the same time that a view change was taking place for the group. (Bug #32738137, Bug #32836868)
• Replication: An incorrect default value in code meant that the allowlist of IP addresses permitted for a replication group was implicitly reconfigured although no value had been supplied. (Bug #32714911)
• Replication: A deadlock could occur if a STOP GROUP_REPLICATION statement was issued when a replication channel on a group member was attempting to commit a transaction. The server now rolls back the transaction immediately if it cannot acquire the relevant lock, rather than waiting for the lock and the commit to complete and causing the deadlock. (Bug #32633176)
• Replication: On a multithreaded replica, the reference to the active event was sometimes managed incorrectly when retrying a transaction. (Bug #32590974)
• Replication: Previously, a warning message was written to the error log if the original commit timestamp on a replicated transaction was more recent than the immediate commit timestamp on the replica applying it. The message could occur inappropriately if the fluctuation in the replication lag had a similar value to the clock difference between the machines involved, which could be made more likely by better quality connections between them. In the event of a Group Replication failover procedure, it was possible for a message to be returned for every transaction, flooding the log. To avoid this situation, the warning message has been withdrawn. (Bug #32554807)
• Replication: After a DML operation was performed on the last partition of a table with more than 128 partitions, MySQL Server and MySQL clients (such as mysqlbinlog) parsed the event information from the binary log incorrectly, resulting in an inaccurate partition ID being stated. The information is now read using an event reader function that is endianness independent. (Bug #32358736, Bug #102191)
• Replication: In a new MySQL Server installation, the mysql.gtid_executed system table was missing the property STATS_PERSISTENT=0 to disable persistent statistics, which is present for the other replication-related tables. (Bug #32250735)
• Replication: When the same row in a table was updated multiple times by the same event, the replication applier’s hash scan algorithm omitted to check for JSON partial updates, which are logged when binlog_row_value_options=PARTIAL_JSON is set. This could result in replication stopping with a “key not found” error. (Bug #32221703)
• Replication: Replica servers now check and validate the transaction ID part of a GTID before applying and committing the transaction associated with it. (Bug #32103192)
• Replication: With the Group Replication system variable group_replication_consistency = AFTER set, if a view change event was delayed until after a locally prepared transaction was completed, a different GTID could be applied to it, causing errors in replication. The data is now processed in the same sequence it is received to avoid the situation. (Bug #31872708)
• Replication: Replication could stop on a multithreaded replica if a unique secondary key was omitted from the writeset hashes used to compute transaction dependencies, leading to errors when executing the transactions on the multithreaded replica. Write set hashes now always include unique secondary keys even if they are not included in the read set and write set. (Bug #31636339)
• Replication: On a multithreaded replica (with slave_parallel_workers > 0 ), the algorithm used by GTID auto-positioning to check for missing transactions briefly sets a low value (4) for the event position in the course of its calculations. If the operation is stopped at that moment, the recovery process that resolves gaps in the sequence of transactions can fail. The process to resolve gaps is not actually necessary when GTID auto-positioning is used, so the process has now been disabled in that situation.

  As a result, on a multithreaded replica, when GTID_MODE = ON is set for the instance and SOURCE_AUTO_POSITION is set for the channel using the CHANGE REPLICATION SOURCE TO statement, the following behaviors now apply:

  • A START REPLICA UNTIL SQL_AFTER_MTS_GAPS statement just stops the applier thread when it finds the first event to execute, and does not attempt to check for gaps in the sequence of transactions.
  • A CHANGE REPLICATION SOURCE TO statement does not automatically fail if there are gaps in the sequence of transactions.

  These changed behaviors only apply on a multithreaded replica that uses GTIDs and GTID auto-positioning, and not on a replica that uses binary log position-based replication. (Bug #30571587, Bug #97694)

• Microsoft Windows: Writing to Windows event logs could be unsuccessful. (Bug #32890918)
• JSON: Reading JSON values from tables that used the CSV storage engine raised an error such as Cannot create a JSON value from a string with CHARACTER SET ‘binary’. This happened because the CSV engine uses my_charset_bin as the character set for the record buffer but creation of JSON values includes an explicit check for my_charset_bin, and raises an error if this character set is given.

  We handle this issue by passing the actual character set of the column instead of the character set of the buffer holding the data, which is always binary. (Bug #102843, Bug #32597017)

• A query for which the derived condition pushdown optimization could be applied was not so optimized when the query was part of INSERT ... SELECT. (Bug #32959186)
• Import operations for access privilege information became very slow for large numbers of accounts and schemas. (Bug #32934351)
• Queries which needed to sort the results of a full-text index scan were in some circumstances not handled correctly. (Bug #32924198)
• Thanks to Xiaoyu Wang for a code correction to PFS_notification_registry::is_empty(). (Bug #32919118, Bug #103788)
• Queries containing GROUP BY, ORDER BY, and LIMIT in a subquery and accessed using a cursor could cause a server exit. (Bug #32918240)
• When invoked with the --help and --verbose options, mysqld created an auto.cnf file in the current directory. (Bug #32906164)
• Queries that involved pushing a condition with view references down to a materialized derived table could cause a server exit. (Bug #32905044, Bug #32324234)
• Messages for ER_CANT_INITIALIZE_UDF errors could be truncated. (Bug #32891703)
• A regression was found in the simplification of streaming aggregation (GROUP BY of data already sorted) that was performed in MySQL 8.0.23.

  We fix this issue as follows: When there is an implicit grouping on a single table which is the subject of a fulltext search, we now force insertion of a temporary table to materialize MATCH() temporaries before they are sent to the AggregateIterator, since it tries to save and restore the rows it receives, but cannot properly include the fulltext search information, as it is hidden. (Bug #32889491)

  References: This issue is a regression of: Bug #31790217.

• For conversion of -DBL_MAX to string and back to double, the new double value differed from the original and was rejected as out of bounds. (Bug #32888982, Bug #103709)
• Now, whenever the JSON_LENGTH() function includes the optional path argument, the server rewrites it as JSON_LENGTH(JSON_EXTRACT(doc, path)). This means that JSON_LENGTH() now supports wildcards (such as $, ., and *) and array ranges in the path, as shown here:
  Press CTRL+C to copy

  mysql> SELECT JSON_LENGTH('[1,2,3,4,5,6,7]', '$[2 to 4]') AS x;
  +------+
  | x    |
  +------+
  |    3 |
  +------+

  (Bug #32877703)

• For flags typically used for RPM and Debian packages, the new WITH_PACKAGE_FLAGS CMake option controls whether to add those flags to standalone builds on those platforms. The default is ON for nondebug builds. This is used to “harden” the builds; for example, by adding -D_FORTIFY_SOURCE=2. (Bug #32876974)
• The NULLIF() function did not perform all necessary checks for errors. (Bug #32865008)
• For views that depended on other views, output from the SHOW CREATE VIEW statement used during production of dump files could cause an error at restore time. (Bug #32854203, Bug #103583)
• The query-attributes code did not properly handle large 64-bit numbers. (Bug #32847269)
• Information retrieved from the Performance Schema metadata_locks table could be incorrect for foreign keys and CHECK constraints. (Bug #32832004, Bug #103532)
• When generating unique names for view columns, the server now considers only those objects whose names are visible. (Bug #32821372)
• When a condition is pushed down to a materialized derived table, a clone of the derived table expression replaces the column (from the outer query block) in the condition. When the cloned item included a FULLTEXT function, it was added to the outer query block instead of the derived table query block, which led to problems. To fix this, we now use the derived query block to clone such items. (Bug #32820437)
• A common table expression which was used more than once in a statement, at least once within a subquery that was subsequently removed during resolution due to being always true, or always false. (Bug #32813547, Bug #32813554)
• If a statement is prepared against a table that is persistent at preparation time but temporary at the time of first execution, an assertion could be raised. (Bug #32799797)
• An internal function used by spatial functions could reference memory after freeing it. (Bug #32793104)
• The impossible filter optimization removed MRR access paths that were required by the corresponding BKA access paths. (Bug #32787415)
• The new WITH_AUTHENTICATION_CLIENT_PLUGINS CMake option is enabled automatically if any corresponding server authentication plugins are built. Its value thus depends on other CMake options and it should not be set explicitly. (Bug #32778378)
• The MRR iterator normally filters out NULL keys by checking impossible_null_ref(), but when a join condition either contained an IS NULL predicate, or used the NULL-safe equals operator ≪=>, the optimizer had to check whether the join condition used the predicate terms as part of its join condition, and not set the internal flag HA_MRR_NO_NULL_ENDPOINTS in such cases. Now we check, using a bitmask, whether the each column in the key rejects NULL, in which case we can set HA_MRR_NO_NULL_ENDPOINTS without further checks. (Bug #32774281)
• For system variables with an enumeration type, SET PERSIST_ONLY var_name = DEFAULT persisted the numeric value and not the symbolic name. (Bug #32761053)
• The X DevAPI operations Collection.replaceOne and Collection.addOrReplaceOne now verify that the value of the _id field in a document matches the id parameter specified for the operation. If it does not, an error is returned. (Bug #32753547)
• For applications that use the C API to execute prepared statements, query attributes could not be used for prepared statements with no parameters. (Bug #32753030, Bug #32790714, Bug #32955044)
• The arguments to IN() were not always converted to the correct character set. (Bug #32746552)
• The LOCATE() function unconditionally returned NULL when an argument could not be evaluated. Now, when used in an expression that is determined to be non-nullable, the function returns zero instead. (Bug #32746536)
• The internal function my_well_formed_len_utf32() asserted when presented with a string of invalid length. Now in such cases, the function reports an invalid string instead. (Bug #32745294)
• The functions TRIM(), RTRIM(), and LTRIM() did not always perform proper error checking. (Bug #32744772)
• A previous fix in an internal resolver function ensured that it raises an error when a generated column cannot be resolved. This worked without any problem when the generated column is part of a CREATE TABLE statement, but in the case where the table with the generated column was generated on a MySQL 5.7 database and then upgraded to MySQL 8.0, an error was reported and the upgrade terminated.

  We fix this by using the correct pointer when reporting the table causing the error in the function fix_generated_columns_for_upgrade(). (Bug #32738972)

• When looking inside rollup wrappers in the SELECT list, and trying to find the same item in the GROUP BY list, the server did not take into account that a cache might have been added around the expression. Now any such caches are unwrapped before looking for the item. (Bug #32729377, Bug #32918400)
• A prepared statement that used MIN() or MAX() could return an incorrect result if it also included dynamic parameters. (Bug #32713860, Bug #103170)
• Replication could fail if a DML statement was executed immediately after an XA transaction was rejected or forced to rollback due to a deadlock. (Bug #32707060)
• Queries containing multiple instances of GROUPING() were not always handled correctly. (Bug #32695103)
• When executing EXPLAIN ANALYZE, materialization iterators count every single init() call, even those that only retain existing data, causes materializations to appear to cost too little compared to the number of underlying calls. We fix this by allowing the materialization iterator to override the call and row counts with its own data. (Bug #32688540)
• A race condition in the metadata locking code could result in a server exit. (Bug #32686116)
• An index-only scan on a covering full-text index could return incorrect results for queries with multiple calls to MATCH() function depending on the order in which the MATCH() calls were evaluated. (Bug #32685616)
• Including query attributes for a prepared statement could cause a statement execution failure. (Bug #32676878)
• Replicated transactions in GTID-based replication include an original_commit_timestamp to show when the transaction was committed on the original source server, and an immediate_commit_timestamp to show when it was committed on the replica. Previously, the original_commit_timestamp was not set for Group Replication’s view change events, which are agreed by the group but then generated and applied by each group member, so the timestamp appeared as zero in viewable output. For improved observability, group members now set local timestamp values for transactions associated with view change events. (Bug #32668567)
• Executing DDL statements on a system table could cause a server exit. (Bug #32665990)
• With the --online-migration option, mysql_migrate_keyring could exit during connection establishment to the migration server. (Bug #32651203)
• mysql_migrate_keyring failed to enforce the condition that the source and destination keystores must differ. (Bug #32637784)
• System cache size checking could be inaccurate on Ubuntu. (Bug #32619199, Bug #102926)
• The server did not process correctly some queries that used MATCH ... AGAINST on a column with a fulltext index in a HAVING clause. (Bug #32617181)

  References: This issue is a regression of: Bug #30969045.

• Replicated transactions in GTID-based replication include an original_commit_timestamp to show when the transaction was committed on the original source server, and an immediate_commit_timestamp to show when it was committed on the replica. Previously, Group Replication servers set the original_commit_timestamp when they committed locally generated transactions, but they did not set the immediate_commit_timestamp. For improved observability, group members now set this timestamp. If the transaction originated in the group, the original_commit_timestamp and immediate_commit_timestamp are both generated by Group Replication, and are equal. If the transaction originated outside the group, the original_commit_timestamp is preserved, and an immediate_commit_timestamp is set. (Bug #32613896)
• The internal function Item_func_match::eq() raised an assert failure in debug builds when it was called with an argument that was an Item_func_match_predicate. The assertion was added with the expectation that an Item_func_match object would not be compared with an Item_func_match_predicate object, but it was later found that this can happen during the ONLY_FULL_GROUP_BY check when the predicate is in a HAVING clause.

  We fixe this by removing the assertion so that the function returns false, instead. (Bug #32611913)

• SELECT using DISTINCT with a GROUP BY ... WITH ROLLUP on a primary key column returned a different result than when the column was not a primary key. (Bug #32565875)
• When an item in the SELECT list came from a table that was found to be constant, it was possible to add caches around it before adding ROLLUP wrappers, causing it to be unfindable in the group list (which had no such wrappers). This is addressed by unwrapping the caches. (Bug #32559356)
• The C client library could produce a Malformed communication packet error if a prepared statement parameter was longer than 8KB and the next parameter represented a NULL value. (Bug #32558782)
• When comparing arguments of different types, and the arguments are deemed constants, the server may insert its own hidden item cache to save on repeated conversion (and possible warnings). This is not visible in the output of any statements such as EXPLAIN.

  An issue arose due to the fact that resolution of ROLLUP runs after the comparisons are set up, and may replace the arguments, which could lead to incorrect results from comparisons. Now when this happens, we signal that the comparison needs to reconsider its caches, and not possibly re-use stale values. (Bug #32548377)

• Incorrect reference counting for a destructor in the implementation of a loadable function could raise an assertion for debug builds or report that the function does not exist for nondebug builds. (Bug #32528898, Bug #102649)
• MySQL source distributions now bundle the Google Test source code, which no longer need be downloaded to run Google Test-based unit tests. Consequently, the WITH_GMOCK and ENABLE_DOWNLOADS CMake options have been removed and are ignored if specified.

  This change also corrects a couple of build issues whereby source distributions incorrectly included an empty source_downloads directory, and CMake did not fail when WITH_UNIT_TESTS was enabled but the Google Test source was not found. (For the latter issue, it can no longer occur because the source is always present.) (Bug #32512077, Bug #27326599, Bug #29935278)

• When outer batched key access and block-nested loop (or hash join) occurred together in a query, both were reverted to nested loops in the plan interpretation to access paths. Problems arose in some cases in which non-equality join conditions had been pushed to a special kind of BKA index condition, and by converting to a regular index lookup (which does not check the BKA condition), it was possible to drop conditions that should have been checked.

  We fix this by removing the BKA index condition; since its use is very rare, potential gains in most practical queries are very low, and removing it decreases complexity significantly. (Bug #32424884)

• SHOW CREATE USER could cause an unexpected server exit if the structure of the mysql.user system table was manually altered. (Bug #32417780, Bug #31654586)
• For large values of the group_concat_max_len system variable, prepared statements that used the GROUP_CONCAT() function could be unnecessarily re-prepared across executions. (Bug #32413530, Bug #102344)
• Changes were not properly rolled back on re-execution of prepared statements or stored procedures for which walk and replace was performed as part of optimization. (Bug #32384324, Bug #32573871)
• Client programs using the asynchronous C API functions could leak memory if a connection timeout occurred. Thanks for Facebook for a contribution used in fixing this issue. (Bug #32372038, Bug #102189, Bug #32800091, Bug #103409)
• The dynamic statistics cache exposed by the INFORMATION_SCHEMA could be updated in the middle of a transaction before it was known whether the transaction would commit, potentially caching information corresponding to no committed state. (Bug #32338335)
• Repreparation of a prepared statement at the beginning of an implicit transaction could cause an ER_GTID_NEXT_TYPE_UNDEFINED_GROUP error. (Bug #32326510, Bug #102031)
• USING HASH was removed from the definitions of Performance Schema thread pool tables because the Performance Schema does not support hash indexes. (Bug #32194617)
• Inserting a datetime literal with an explicit time zone offset into a TIMESTAMP column could produce the wrong time if time_zone=SYSTEM and the system time zone has DST transitions. (Bug #32173664, Bug #101670)
• While setting up ORDER BY for a window function, a window definition including a subquery was removed along with the subquery in the ORDER BY. (Bug #32103260)
• The use of a SET PERSIST or SET PERSIST_ONLY statement is now disallowed for the group_replication_force_members system variable. This system variable must be cleared after use before you can issue a START GROUP_REPLICATION statement, so it should not be persisted to the MySQL server instance’s option file. (Bug #31983203)
• Upgrades from MySQL 5.7 to 8.0 failed if the MySQL installation had FEDERATED tables. (Bug #31973053)
• Persisting component-related system variables could result in unnecessary “unknown variable” error messages. (Bug #31968366)
• An out-of-memory error occurred when loading large amounts of data into tables with full-text search indexes. Not all of the memory allocated to the full-text search cache was accounted for when inserting data into the full-text search auxiliary tables. (Bug #31576731)
• The precision for a UNION between integer and decimal values could be calculated incorrectly, leading to truncation of the integer in the result. (Bug #31348202, Bug #99567)
• InnoDB wrote unnecessary warnings to the error log indicating that table statistics could not be calculated. (Bug #30865032)
• A secondary index over a virtual column became corrupted when the index was built online.

  For UPDATE statements, we fix this as follows: If the virtual column value of the index record is set to NULL, then we generate this value from the cluster index record. (Bug #30556595)

• DROP DATABASE for a database with a large number of tables (one million) could result in an out-of-memory condition. (Bug #29634540)
• The system_time_zone system variable is initialized at server startup from the server host settings and the mysqld environment, but if the server host time zone changed (for example, due to daylight saving time), system_time_zone did not reflect the change. Now it does. (Bug #29330089, Bug #94257)
• For upgrades on Ubuntu, if an existing my.cnf file is found, it is renamed to my.cnf.bak and a warning is issued. (Bug #24486556, Bug #82639)
• Boolean system variables could be assigned a negative value. (Bug #11758439, Bug #50643)
• Prepared statements did not always make use of index extensions (see Use of Index Extensions). (Bug #103711, Bug #32897525)

  References: See also: Bug #103710, Bug #32897503.

• When enabled, the prefer_ordering_index optimizer switch had a negative effect on the performance of prepared statements. (Bug #103710, Bug #32897503)

  References: See also: Bug #103711, Bug #32897525.

• Successive INSERT() function calls could sometimes yield invalid NULL results. (Bug #103513, Bug #32824978)
• Some NOT IN subqueries did not return correct results due to a regression in NULL handling. (Bug #103331, Bug #32773801)

  References: This issue is a regression of: Bug #30473261.

• Whenever a SELECT ... FOR UPDATE NOWAIT statement was unable to obtain a record lock, a message Got error 203 when reading table … was written to the error log, even though though this is a relatively common occurrence, the logging of which led to excessive use of disk space.

  Our thanks to Brian Yue for this contribution. (Bug #103157, Bug #32705614)

• 0 - (MAX(BIGINT) + 1) returned -(MAX(BIGINT) + 1). Now an out of range error is returned instead. (Bug #103093, Bug #32693863)

转自 https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-26.html#mysqld-8-0-26-audit-log