Bjorn Munch MySQL Community Server 8.0.0-dmr has been released (part 2/3)
Sep 12, 2016; 16:45
MySQL Community Server 8.0.0-dmr has been released (part 2/3)
[This is part 2 of the announcement]
Performance Schema Notes
* Incompatible Change: The Performance Schema now instruments server errors (and warnings), and exposes statistical information about them through a set of summary tables:
+ The error instrument controls whether error information is collected (enabled by default).
+ Several tables contain error information, summarized in various ways: events_errors_summary_global_by_error, events_errors_summary_by_account_by_error, events_errors_summary_by_host_by_error, events_errors_summary_by_thread_by_error, events_errors_summary_by_user_by_error.
+ The performance_schema_error_size system variable controls the number of instrumented errors. For more information, see Performance Schema Error Summary Tables (http://dev.mysql.com/doc/refman/8.0/en/error-summary-tables.html) If you upgrade to this MySQL release from an earlier version, you must run mysql_upgrade (and restart the server) to incorporate these changes into the performance_schema database. In consequence of the preceding changes, two server error symbols were renamed: ER_CANT_SET_ENFORCE_GTID_CONSISTENCY_ON_WITH_ONGOING_GTID _VIOLATING_TRANSACTIONS is now ER_CANT_ENFORCE_GTID_CONSISTENCY_WITH_ONGOING_GTID_VIOLAT ING_TX and ER_SET_ENFORCE_GTID_CONSISTENCY_WARN_WITH_ONGOING_GTID_VI OLATING_TRANSACTIONS is now ER_ENFORCE_GTID_CONSISTENCY_WARN_WITH_ONGOING_GTID_VIOLAT ING_TX. Also, several server error codes were found to be no longer used in the server and have been removed as obsolete. Applications that test specifically for any of these errors should be updated: ER_BINLOG_READ_EVENT_CHECKSUM_FAILURE ER_BINLOG_ROW_RBR_TO_SBR ER_BINLOG_ROW_WRONG_TABLE_DEF ER_CANT_ACTIVATE_LOG ER_CANT_CHANGE_GTID_NEXT_IN_TRANSACTION ER_CANT_CREATE_FEDERATED_TABLE ER_CANT_CREATE_SROUTINE ER_CANT_DELETE_FILE ER_CANT_GET_WD ER_CANT_SET_GTID_PURGED_WHEN_GTID_MODE_IS_OFF ER_CANT_SET_WD ER_CANT_WRITE_LOCK_LOG_TABLE ER_CREATE_DB_WITH_READ_LOCK ER_CYCLIC_REFERENCE ER_DB_DROP_DELETE ER_DELAYED_NOT_SUPPORTED ER_DIFF_GROUPS_PROC ER_DISK_FULL ER_DROP_DB_WITH_READ_LOCK ER_DROP_USER ER_DUMP_NOT_IMPLEMENTED ER_ERROR_DURING_CHECKPOINT ER_ERROR_ON_CLOSE ER_EVENTS_DB_ERROR ER_EVENT_CANNOT_DELETE ER_EVENT_CANT_ALTER ER_EVENT_COMPILE_ERROR ER_EVENT_DATA_TOO_LONG ER_EVENT_DROP_FAILED ER_EVENT_MODIFY_QUEUE_ERROR ER_EVENT_NEITHER_M_EXPR_NOR_M_AT ER_EVENT_OPEN_TABLE_FAILED ER_EVENT_STORE_FAILED ER_EXEC_STMT_WITH_OPEN_CURSOR ER_FAILED_ROUTINE_BREAK_BINLOG ER_FLUSH_MASTER_BINLOG_CLOSED ER_FORM_NOT_FOUND ER_FOUND_GTID_EVENT_WHEN_GTID_MODE_IS_OFF__UNUSED ER_FRM_UNKNOWN_TYPE ER_GOT_SIGNAL ER_GRANT_PLUGIN_USER_EXISTS ER_GTID_MODE_REQUIRES_BINLOG ER_GTID_NEXT_IS_NOT_IN_GTID_NEXT_LIST ER_HASHCHK ER_INDEX_REBUILD ER_INNODB_NO_FT_USES_PARSER ER_LIST_OF_FIELDS_ONLY_IN_HASH_ERROR ER_LOAD_DATA_INVALID_COLUMN_UNUSED ER_LOGGING_PROHIBIT_CHANGING_OF ER_MALFORMED_DEFINER ER_MASTER_KEY_ROTATION_ERROR_BY_SE ER_NDB_CANT_SWITCH_BINLOG_FORMAT ER_NEVER_USED ER_NISAMCHK ER_NO_CONST_EXPR_IN_RANGE_OR_LIST_ERROR ER_NO_FILE_MAPPING ER_NO_GROUP_FOR_PROC ER_NO_RAID_COMPILED ER_NO_SUCH_KEY_VALUE ER_NO_SUCH_PARTITION__UNUSED ER_OBSOLETE_CANNOT_LOAD_FROM_TABLE ER_OBSOLETE_COL_COUNT_DOESNT_MATCH_CORRUPTED ER_ORDER_WITH_PROC ER_PARTITION_SUBPARTITION_ERROR ER_PARTITION_SUBPART_MIX_ERROR ER_PART_STATE_ERROR ER_PASSWD_LENGTH ER_QUERY_ON_MASTER ER_RBR_NOT_AVAILABLE ER_SKIPPING_LOGGED_TRANSACTION ER_SLAVE_CHANNEL_DELETE ER_SLAVE_MULTIPLE_CHANNELS_HOST_PORT ER_SLAVE_MUST_STOP ER_SLAVE_WAS_NOT_RUNNING ER_SLAVE_WAS_RUNNING ER_SP_GOTO_IN_HNDLR ER_SP_PROC_TABLE_CORRUPT ER_SQL_MODE_NO_EFFECT ER_SR_INVALID_CREATION_CTX ER_TABLE_NEEDS_UPG_PART ER_TOO_MUCH_AUTO_TIMESTAMP_COLS ER_UNEXPECTED_EOF ER_UNION_TABLES_IN_DIFFERENT_DIR ER_UNSUPPORTED_BY_REPLICATION_THREAD ER_UNUSED1 ER_UNUSED2 ER_UNUSED3 ER_UNUSED4 ER_UNUSED5 ER_UNUSED6 ER_VIEW_SELECT_DERIVED_UNUSED ER_WRONG_MAGIC ER_WSAS_FAILED
* Previously, the DIGEST and DIGEST_TEXT columns in the Performance Schema events_statements_current table were populated only after statement execution ended. Now, the columns are populated just after parsing and before statement execution begins. This enables monitoring applications to access statement digest information during statement execution. (Bug #23336542)
* Performance Schema tables now include indexes, which gives the optimizer access to execution plans other than full table scans and makes queries more efficient. Performance Schema table indexes are predefined and cannot be dropped, added, or altered. They are like hash indexes and do not provide row ordering.
* The size of the ROLE column of the setup_actors Performance Schema table was increased from 16 to 32 characters.
* The validate_password_check_user_name system variable is now enabled by default rather than disabled. This means that when the validate_password plugin is enabled, by default it now rejects passwords that match the current session user name.
* The client-side --ssl and --ssl-verify-server-cert options have been removed. Use --ssl-mode=REQUIRED instead of --ssl=1 or --enable-ssl. Use --ssl-mode=DISABLED instead of --ssl=0, --skip-ssl, or --disable-ssl. Use --ssl-mode=VERIFY_IDENTITY instead of --ssl-verify-server-cert options. (The server-side --ssl option remains unchanged.) For the C API, MYSQL_OPT_SSL_ENFORCE and MYSQL_OPT_SSL_VERIFY_SERVER_CERT options for mysql_options() correspond to the client-side --ssl and --ssl-verify-server-cert options and have been removed. Use MYSQL_OPT_SSL_MODE with an option value of SSL_MODE_REQUIRED or SSL_MODE_VERIFY_IDENTITY instead.
Spatial Data Support
* Spatial functions for import and export of Well-Known Text (WKT) values used MySQL 'GEOMETRYCOLLECTION()' nonstandard syntax rather than OpenGIS 'GEOMETRYCOLLECTION EMPTY' standard syntax. Now both syntaxes are understood for import and the standard syntax is used for export. (Bug #23632147, Bug #81964)
* The required version of the Boost library for server builds has been raised from 1.59.0 to 1.60.0. (Bug #79380, Bug #22253921)
* The ST_X() and ST_Y() spatial functions now permit an optional second argument that specifies an X or Y coordinate value, respectively. With two arguments, the function result is the point value from the first argument with the appropriate coordinate modified. In addition, ST_X() and ST_Y() with a single argument now are stricter and produce an ER_UNEXPECTED_GEOMETRY_TYPE error rather than returning NULL if the argument is a valid geometry but not a point. For more information, see Point Property Functions (http://dev.mysql.com/doc/refman/8.0/en/gis-point-property-functions.html).
* The ST_SRID() spatial function now permits an optional second argument that specifies a SRID value. With two arguments, the function result is the geometry value from the first argument with its SRID modified according to the second argument. For more information, see General Geometry Property Functions (http://dev.mysql.com/doc/refman/8.0/en/gis-general-property-functions.html).
* MySQL now supports spatial reference systems other than SRID 0. (Specifically, georeferenced 2D projections.) Information about supported reference systems is stored in the st_spatial_reference_systems data dictionary table.
* In MySQL 5.7, several spatial functions available under multiple names were deprecated to move in the direction of making the spatial function namespace more consistent, the goal being that each spatial function name begin with ST_ if it performs an exact operation, or with MBR if it performs an operation based on minimum bounding rectangles. The deprecated functions have now been removed to leave only the corresponding ST_ and MBR functions:
+ These functions are removed in favor of the MBR names: Contains(), Disjoint(), Equals(), Intersects(), Overlaps(), Within().
* mysql-test-run.pl now supports a --do-suite option, which is similar to --do-test but permits specifying entire suites of tests to run. (Bug #24350345)
* The mysqltest rmdir command fails if the directory to be removed contains any files or directories. To enable recursive removal of a directory as well as its contents, if any, mysqltest now supports a force-rmdir command. (Bug #24316799)
* Two new test suite options make it easier to debug test cases:
+ mysql-test-run.pl supports a --mysqltest=options option that enables options to be passed to mysqltest.
+ mysqltest supports a --trace-exec option that causes it to immediately print output from executed programs to stdout. mysql-test-run.pl now recognizes the MTR_CTEST_TIMEOUT environment variable. If set, the value is a timeout in seconds to pass to ctest unit test commands. (Bug #21821049, Bug #21278845)
* For test cases in the MySQL test suite, it was previously possible to use symbolic error names for the --error command only for server errors. This is now also possible for client errors. For example: --error CR_SERVER_GONE_ERROR
* The mysqltest program now has a copy_files_wildcard command that copies all files that match a pattern from a source directory to a destination directory. See mysqltest Commands (http://dev.mysql.com/doc/mysqltest/2.0/en/mysqltest-commands.html). (Bug #82111, Bug #23743035)
Functionality Added or Changed
* Incompatible Change; Partitioning: The generic partitioning handler has been removed from the MySQL server. As part of this change, mysqld no longer supports the --partition and --skip-partition options, and the server can no longer be built using -DWITH_PARTITION_STORAGE_ENGINE. partition is also no longer displayed in the output of SHOW PLUGINS, or shown in the INFORMATION_SCHEMA.PLUGINS table. In order to support partitioning of a given table, the storage engine used for the table must now provide its own ("native") partitioning handler. InnoDB is the only storage engine supported in MySQL 8.0 which includes a native partitioning handler. An attempt to create partitioned tables in MySQL 8.0 using any other storage engine fails. (The NDB storage engine used by MySQL Cluster also provides its own partitioning handler, but is currently not supported by MySQL 8.0.) Affects on upgrades. The direct upgrade of a partitioned table using a storage engine other than InnoDB (such as MyISAM) from MySQL 5.7 (or earlier) to MySQL 8.0 is not supported. There are two options for upgrading such a table to be compatible with MySQL 8.0, listed here:
+ Remove the table's partitioning; you can do this without any data loss by executing an ALTER TABLE ... REMOVE PARTITIONING statement.
+ Change the storage engine used for the table to InnoDB, using ALTER TABLE ... ENGINE=INNODB; this leaves the table's partitioning in place. At least one of these operations must be performed for any partitioned non-InnoDB table, prior to upgrading the server to MySQL 8.0. Otherwise, such a table cannot be used following the upgrade. An analogous situation is met when importing databases from a dump file that was created in MySQL 5.7 or earlier using mysqldump into a MySQL 8.0 server, due to the fact that table creation statements that would result in a partitioned table using a storage engine without such support fail with an error in MySQL 8.0. For this reason you must ensure that any statements in the dump file creating partitioned tables do not also specify an unsupported storage engine. You can do this either by removing any references to partitioning from CREATE TABLE statements that use a value for the STORAGE ENGINE option other than InnoDB, or by specifying the storage engine as InnoDB (or allowing InnoDB to be used by default). For more information, see Partitioning Limitations Relating to Storage Engines (http://dev.mysql.com/doc/refman/8.0/en/partitioning-limitations-storage-engines.html).
* Important Change; InnoDB: The following InnoDB file format configuration parameters were deprecated in MySQL 5.7.7 and are now removed:
+ innodb_large_prefix File format configuration parameters were necessary for creating tables compatible with earlier versions of InnoDB in MySQL 5.1. Now that MySQL 5.1 has reached the end of its product lifecycle, the parameters are no longer required. The FILE_FORMAT column was removed from the INNODB_SYS_TABLES and INNODB_SYS_TABLESPACES Information Schema tables.
* InnoDB: The innodb_buffer_pool_debug option permits multiple buffer pool instances when the buffer pool is less than 1GB in size, ignoring the 1GB minimum buffer pool size constraint imposed on innodb_buffer_pool_instances. (Bug #24287290)
* InnoDB: A new dynamic configuration option, innodb_deadlock_detect, can be used to disable deadlock detection. On high concurrency systems, deadlock detection can cause a slowdown when numerous threads wait for the same lock. At times, it may be more efficient to disable deadlock detection and rely on the innodb_lock_wait_timeout setting for transaction rollback when a deadlock occurs. (Bug #23477773)
* InnoDB: The libinnodb_zipdecompress.a library allows external tools to use the page_zip_decompress_low() function to decompress InnoDB pages. (Bug #21405300, Bug #77664)
* InnoDB: To address contention that could occur under some workloads, the buffer pool mutex was removed and replaced by several list and hash protecting mutexes. Also, several buffer pool related variables no longer require buffer pool mutex protection. Thanks to Yasufumi Kinoshita and Laurynas Biveinis for the patch. (Bug #20381905, Bug #75534)
* InnoDB: InnoDB now avoids intermediate commits that would occur every 10000 rows during ALTER TABLE ALGORITHM=COPY operations. The purpose of intermediate commits was to speed up recovery in the case of an aborted ALTER TABLE ALGORITHM=COPY operation. If an ALTER TABLE ALGORITHM=COPY operation is aborted, the new, uncommitted table is now dropped during DDL log recovery before the undo log is rolled back, thereby avoiding time-consuming data rollback for the uncommitted table. Undo logging is now suppressed for ALTER TABLE ALGORITHM=COPY operations unless there is an IGNORE clause or something else that requires rollback capability. If there is full-text index on the table being altered, full-text data is inserted into full-text auxiliary tables as the ALTER TABLE ALGORITHM=COPY operation inserts rows into the new, uncommitted table. Previously, full-text data was only processed on transaction commit. (Bug #17479594)
* InnoDB: To reduce read-write lock contention that can result from multiple purge threads purging rows from the same table, undo records are now grouped and assigned to different purge threads by table ID.
* InnoDB: InnoDB code now uses the C++ std::thread library for thread management.
* InnoDB: BLOB code was refactored to provide an internal C++ interface for operations on compressed and uncompressed BLOB data.
* InnoDB: The InnoDB memcached plugin now supports range queries and fetching multiple key value pairs in a single memcached query.
* InnoDB: The current maximum auto-increment counter value is now written to the redo log each time the value changes, and it is saved to an engine-private system table on each checkpoint. These changes make the current maximum auto-increment counter value persistent across server restarts. Additionally:
+ A server restart no longer cancels the effect of the AUTO_INCREMENT = N table option. If you initialize the auto-increment counter to a specific value, or if you alter the auto-increment counter value to a larger value, the new value is persisted across server restarts.
+ A server restart immediately following a ROLLBACK operation no longer results in the reuse of auto-increment values that were allocated to the rolled-back transaction.
+ If you modify an AUTO_INCREMENT column value to a value larger than the current maximum auto-increment value (in an UPDATE operation, for example), the new value is persisted, and subsequent INSERT operations allocate auto-increment values starting from the new, larger value. For more information, see AUTO_INCREMENT Handling in InnoDB (http://dev.mysql.com/doc/refman/8.0/en/innodb-auto-increment-handling.html), and InnoDB AUTO_INCREMENT Counter Initialization (http://dev.mysql.com/doc/refman/8.0/en/innodb-auto-increment-handling.html#innodb-auto-increment-initialization).
* InnoDB: The innodb_stats_sample_pages system variable was removed. innodb_stats_sample_pages was deprecated in MySQL 5.6.3 and replaced by innodb_stats_transient_sample_pages.
* InnoDB: When encountering index tree corruption, InnoDB writes a corruption flag to the redo log, which makes the corruption flag crash-safe. InnoDB also writes in-memory corruption flag data to an engine-private system table on each checkpoint. During recovery, InnoDB reads corruption flags from both locations and merges results before marking in-memory table and index objects as corrupt.
* InnoDB: The innodb_locks_unsafe_for_binlog system variable was removed.
* InnoDB: InnoDB no longer creates .isl files (InnoDB Symbolic Link files) when creating tablespace data files outside of the MySQL data directory. Redo log records are now used to locate remote tablespaces. With this change, moving a remote tablespace while the server is offline by manually modifying an .isl file is no longer supported.
* InnoDB: InnoDB no longer supports compressed temporary tables. When innodb_strict_mode is enabled (the default), CREATE TEMPORARY TABLE returns an error if ROW_FORMAT=COMPRESSED or KEY_BLOCK_SIZE is specified. If innodb_strict_mode is disabled, warnings are issued and the temporary table is created using a non-compressed row format. With this change, all temporary tables are created in the shared temporary tablespace, ibtmp1. The PER_TABLE_TABLESPACE and IS_COMPRESSED columns were removed from the INFORMATION_SCHEMA.INNODB_TEMP_TABLE_INFO.
* InnoDB: A new INFORMATION_SCHEMA table, INNODB_CACHED_INDEXES, reports the number of index pages cached in the InnoDB buffer pool for each index.
* InnoDB: The innodb_checksums system variable was removed. innodb_checksums was replaced by innodb_checksum_algorithm in MySQL 5.6.3.
* InnoDB: InnoDB startup code was refactored.
* InnoDB: The innodb_flush_method default value is no longer NULL. On Unix-like systems, the default value is fsync. On Windows systems, the default value is unbuffered. On Windows, the innodb_flush_method setting no longer affects the innodb_use_native_aio setting. There are now two possible settings for innodb_flush_method on Windows, unbuffered (unbuffered I/O) and normal (buffered I/O). With this change, you can enable asynchronous I/O with buffered I/O, which is a new combination (innodb_use_native_aio=ON and innodb_flush_method=normal). The async_unbuffered setting was removed. You can now set innodb_flush_method and innodb_change_buffering configuration options using numeric values.
* InnoDB: The innodb_support_xa system variable, which enables support for two-phase commit in XA transactions, was removed. As of MySQL 5.7.10, InnoDB support for two-phase commit in XA transactions is always enabled.
* InnoDB: The new INFORMATION_SCHEMA.INNODB_CACHED_INDEXES table reports the number of index pages cached in the InnoDB buffer pool for each index.
* InnoDB: InnoDB no longer creates an .isl file (InnoDB Symbolic Link files) when creating a file-per-table tablespace data file outside of the MySQL data directory. InnoDB now uses the redo log to locate remote tablespace data files. Offline relocation of a file-per-table tablespace data file created outside of the MySQL data directory by modifying the .isl file is no longer supported.
* Replication: There are two improvements to how a CHANGE MASTER TO (http://dev.mysql.com/doc/refman/8.0/en/change-master-to.html) statement is written into the error log (mysqld.log):
+ Before, no commas were put between the option specifications (for example MASTER_USER = and MASTER_PASSWORD = ), so users who wanted to use the statement by copy and paste had to insert the commas manually. Commas are now inserted when the statement is written to the error log.
+ When the literal "<secret>" is inserted as a placeholder for the MASTER_PASSWORD value, no quotes are used now, so users who forget to replace the literal with the real password before a copy and paste gets a syntax error immediately, instead of running into other issues. (Bug #18194384)
* Replication: It is now possible to restore a backup of a GTID-based replication server because you can add GTIDs to gtid_purged, regardless of whether gtid_executed is empty or not. This enables you to restore backups from GTID-based replication servers without losing existing GTID information and binary logs. The GTIDs to add are those which existed in gtid_executed at the time of taking the backup. The syntax for SET GTID_PURGED has been extended to enable this ability, for example SET GTID_PURGED ="+gtid_set" adds gtid_set to the existing gtid_purged GTID set.
* To produce more accurate estimates, the MEMORY storage engine now calculates index statistics (records per key estimates) using floating-point rather than integer arithmetic. (Bug #23024059)
* A new CMake option, INSTALL_STATIC_LIBRARIES, enables control over whether to install static libraries. The default is ON. If set to OFF, these libraries are not installed: libmysqlclient.a, libmysqld.a, libmysqlservices.a. (Bug #22891432)
* The internal mysql_prepare_create_table() server function has been refactored for improved code maintainability and clarity. This code revision results in the following minor changes of behavior for CREATE TABLE and ALTER TABLE:
+ Attempts to create a second primary key based on a NULL column now produce an ER_MULTIPLE_PRI_KEY error rather than ER_PRIMARY_CANT_HAVE_NULL.
+ Attempts to create a second primary key based on a generated column now produce an ER_MULTIPLE_PRI_KEY error rather than ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN.
+ Attempts to create a full-text key on a JSON column now produce an ER_JSON_USED_AS_KEY error rather than ER_BAD_FT_COLUMN.
+ Attempts to create a key in a storage engine that does not support keys (for example, EXAMPLE) now produce an ER_TOO_MANY_KEYS error rather than ER_TOO_MANY_KEY_PARTS. (Bug #22884886)
* Previously, the Performance Schema was not built for libmysqld, the embedded server. This prevented use of the SHOW STATUS and SHOW VARIABLES statements with show_compatibility_56=OFF because, with that setting, those statements take their results from Performance Schema tables. Now for libmysqld, the required Performance Schema tables are built (with no instrumentation collected), so that those SHOW statements can be supported with show_compatibility_56=OFF. (Bug #22809694)
* Several internal functions used by JSON_CONTAINS(), JSON_SEARCH(), and other MySQL JSON functions created excessive numbers of local copies of keys, values, or both, when performing inspections of JSON objects. Such copying has been eliminated or reduced in many cases. In addition, the lifetimes of temporary objects used by some of these functions have been reduced. These changes should make these and related JSON functions perform more efficiently than previously, and with fewer resources required. (Bug #22602142)
* If the system lz4 and openssl zlib commands are available, the lz4_decompress and zlib_decompress utilities are unneeded. Two changes enable those utilities not to be built: If the new WITH_LZ4 CMake option is set to system, lz4_decompress is not built or installed. If the WITH_ZLIB CMake option is set to system, zlib_decompress is not built or installed. (Bug #22329851)
* Source files for the MySQL strings library have been converted from C (.c suffix) to C++ (.cc suffix). This enables stricter compilation checks and use of C++ features in the library code. (Bug #22124719)
* Source code for the mysys library now uses C++ rather than C to take advantage of stricter compilation checks and permit use of C++ features. (Bug #21881278)
* A new CMake option, WITH_TSAN, permits enabling ThreadSanitizer for compilers that support it. (Bug #80409, Bug #23171902)
* This release adds an unquoting extraction operator ->>, sometimes also referred to as an inline path operator, for use with JSON documents stored in MySQL. The new operator is similar to the -> operator, but performs JSON unquoting of the value as well. For a JSON column mycol and JSON path expression mypath, the following three expressions are equivalent:
+ JSON_UNQUOTE( JSON_EXTRACT(mycol, "$.mypath") )
+ mycol->>"$.mypath" The ->> operator can be used in SQL statements wherever JSON_UNQUOTE(JSON_EXTRACT()) would be allowed. This includes (but is not limited to) SELECT lists, WHERE and HAVING clauses, and ORDER BY and GROUP BY clauses. For more information, see Functions That Search JSON Values (http://dev.mysql.com/doc/refman/8.0/en/json-search-functions.html), and JSON Path Syntax (http://dev.mysql.com/doc/refman/8.0/en/json-path-syntax.html). (Bug #78736, Bug #21980346)
* The global list of connections, previously protected by a single mutex, has been partitioned into eight parts, each protected by its own instance of the mutex. The result is a reduction of overhead and improved performance for connection processing. An implication of this change for monitoring purposes is that the Performance Schema now exposes eight different instances each of the LOCK_thd_list mutex, LOCK_thd_remove mutex, and COND_thd_list condition variable.
* MySQL now provides functions to manipulate UUID values and make them easier to work with:
+ UUID_TO_BIN() and BIN_TO_UUID() convert between UUID values in string and binary formats (represented as hexadecimal characters and VARBINARY(16), respectively). This permits conversion of string UUID values to binary values that take less storage space. UUID values converted to binary can be represented in a way that permits improved indexing efficiency.
+ IS_UUID() returns 1 or 0 to indicate whether its argument is a valid string-format UUID value. For more information about these functions, see Miscellaneous Functions (http://dev.mysql.com/doc/refman/8.0/en/miscellaneous-functions.html)
* The mysql_plugin utility has been removed. Alternatives include loading plugins at server startup using the --plugin-load or --plugin-load-add option, or at runtime using the INSTALL PLUGIN statement.
* The server now relies on storage engines to clean up temporary tables left from previous server runs. InnoDB does this by discarding the temporary tablespace on restart. MyISAM and other similar storage engines still rely on scanning the temporary directory to detect leftover tables, by looking for files belonging to these engines with a certain name pattern.
* The deprecated mysql_shutdown() C API function and corresponding COM_SHUTDOWN client/server protocol command have been removed. Instead, use mysql_query() to execute a SHUTDOWN statement.
* Work was done to clean up the source code base, including: Removal of unneeded CMake checks; removing unused macros from source files; reorganizing header files to reduce the number of dependencies and make them more modular, removal of function declarations without definitions.
* The server no longer performs conversion of pre-MySQL 5.1 database names containing special characters to 5.1 format with the addition of a #mysql50# prefix. Because these conversions are no longer performed, the --fix-db-names and --fix-table-names options for mysqlcheck, the UPGRADE DATA DIRECTORY NAME clause for the ALTER DATABASE statement, and the Com_alter_db_upgrade status variable have been removed. Upgrades are supported only from one major version to another (for example, 5.0 to 5.1, or 5.1 to 5.5), so there should be little remaining need for conversion of older 5.0 database names to current versions of MySQL. As a workaround, upgrade a MySQL 5.0 installation to MySQL 5.1 before upgrading to a more recent release.
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