[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.

Security Notes

* 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().

+ These functions are removed in favor of the ST_
names: Area(), AsBinary(), AsText(), AsWKB(),
AsWKT(), Buffer(), Centroid(), ConvexHull(),
Crosses(), Dimension(), Distance(), EndPoint(),
Envelope(), ExteriorRing(), GeomCollFromText(),
GeomCollFromWKB(), GeomFromText(), GeomFromWKB(),
GeometryCollectionFromText(),
GeometryCollectionFromWKB(), GeometryFromText(),
GeometryFromWKB(), GeometryN(), GeometryType(),
InteriorRingN(), IsClosed(), IsEmpty(), IsSimple(),
LineFromText(), LineFromWKB(), LineStringFromText(),
LineStringFromWKB(), MLineFromText(),
MLineFromWKB(), MPointFromText(), MPointFromWKB(),
MPolyFromText(), MPolyFromWKB(),
MultiLineStringFromText(), MultiLineStringFromWKB(),
MultiPointFromText(), MultiPointFromWKB(),
MultiPolygonFromText(), MultiPolygonFromWKB(),
NumGeometries(), NumInteriorRings(), NumPoints(),
PointFromText(), PointFromWKB(), PointN(),
PolyFromText(), PolyFromWKB(), PolygonFromText(),
PolygonFromWKB(), SRID(), StartPoint(), Touches(),
X(), Y().

+ GLength() is removed in favor of ST_Length().

Test Suite Notes

* 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

(Bug #21048973)

* 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_file_format

+ innodb_file_format_check

+ innodb_file_format_max

+ 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") )

+ JSON_UNQUOTE(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.

[...continued...]

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