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MySQL Community Server 8.0.23 has been released [ part 2/2 ]
Posted by: Bjørn Munch
Date: January 18, 2021 08:01AM

[ This is part 2 of the announcement ]

Bugs Fixed

     * InnoDB: A CREATE TABLE operation that specified the
       COMPRESSION option was permitted with a warning on a
       system that does not support hole punching. The operation
       now fails with an error instead. (Bug #32174200)

     * InnoDB: A MySQL DB system restart following an upgrade
       that was initiated while a data load operation was in
       progress raised an assertion failure. (Bug #32173596)

     * InnoDB: An error message regarding the number of truncate
       operations on the same undo tablespace between
       checkpoints incorrectly indicated a limit of 64. The
       limit was raised from 64 to 50,000 in MySQL 8.0.22. (Bug
       #32151601, Bug #101601)

     * InnoDB: rw_lock_t and buf_block_t source code structures
       were reduced in size. (Bug #32084500)

     * InnoDB: An InnoDB transaction became inconsistent after
       creating a table using a storage engine other than InnoDB
       from a query expression that operated on InnoDB tables.
       (Bug #32079103)

     * InnoDB: In some circumstances, such as when an existing
       gap lock inherits a lock from a deleted record, the
       number of locks that appear in the
       INFORMATION_SCHEMA.INNODB_TRX table could diverge from
       the actual number of record locks.
       Thanks to Fungo Wang from Alibaba for the patch. (Bug
       #32068538, Bug #101305)

     * InnoDB: An off-by-one error in Fil_system sharding code
       was corrected, and the maximum number of shards
       (MAX_SHARDS) was changed to 69. (Bug #32052821, Bug
       #101260)

     * InnoDB: The TempTable storage engine memory allocator
       allocated extra blocks of memory unnecessarily. (Bug
       #32018553)

     * InnoDB: A SELECT COUNT(*) operation on a table containing
       uncommitted data performed poorly due to unnecessary I/O.
       Thanks to Brian Yue for the contribution. (Bug #31997733,
       Bug #100966)

     * InnoDB: A race condition when shutting down the log
       writer raised an assertion failure. (Bug #31997362)

     * InnoDB: Page cleaner threads were not utilized optimally
       in sync-flush mode, which could cause page flush
       operations to slow down or stall in some cases.
       Sync-flush mode occurs when InnoDB is close to running
       out of free space in the redo log, causing the page
       cleaner coordinator to initiate aggressive page flushing.
       (Bug #31994031)

     * InnoDB: A high frequency of updates while undo log
       truncation was enabled caused purge to lag. The lag was
       due to the innodb_purge_rseg_truncate_frequency setting
       being changed temporarily from 128 to 1 when an undo
       tablespace was selected for truncation. The code that
       modified the setting has been removed. (Bug #31991688)

     * InnoDB: Automated truncation of undo tablespaces caused a
       performance regression. To address this issue, undo
       tablespace files are now initialized at 16MB and extended
       by a minimum of 16MB. To handle aggressive growth, the
       file extension size is doubled if the previous file
       extension happened less than 0.1 seconds earlier.
       Doubling of the extension size can occur multiple times
       to a maximum of 256MB. If the previous file extension
       occurred more than 0.1 seconds earlier, the extension
       size is reduced by half, which can also occur multiple
       times, to a minimum of 16MB. Previously, the initial size
       of an undo tablespace depended on the InnoDB page size,
       and undo tablespaces were extended four extents at a
       time.
       If the AUTOEXTEND_SIZE option is defined for an undo
       tablespace, the undo tablespace is extended by the
       greater of the AUTOEXTEND_SIZE setting and the extension
       size determined by the logic described above.
       When an undo tablespace is truncated, it is normally
       recreated at 16MB in size, but if the current file
       extension size is larger than 16MB, and the previous file
       extension happened within the last second, the new undo
       tablespace is created at a quarter of the size defined by
       the innodb_max_undo_log_size variable.
       Stale undo tablespace pages are no longer removed at the
       next checkpoint. Instead, the pages are removed in the
       background by the InnoDB master thread. (Bug #31965404,
       Bug #32020900, Bug #101194)

     * InnoDB: A posix_fallocate() failure while preallocating
       space for a temporary tablespace raised an error and
       caused an initialization failure. A warning is now issued
       instead, and InnoDB falls back to the
       non-posix_fallocate() method for preallocating space.
       (Bug #31965379)

     * InnoDB: An invalid pointer caused a shutdown failure on a
       MySQL Server compiled with the DISABLE_PSI_MEMORY source
       configuration option enabled. (Bug #31963333)

     * InnoDB: A long SX lock held by an internal function that
       calculates new statistics for a given index caused a
       failure. (Bug #31889883)

     * InnoDB: The INFORMATION_SCHEMA.INNODB_TABLESPACES table
       reported a FILE_SIZE of 0 for some tables and schemas.
       When the associated tablespace was not in the memory
       cache, the tablespace name was used to determine the
       tablespace file name, which was not always a reliable
       method. The tablespace ID is now used instead. Using the
       tablespace name remains as a fallback method. (Bug
       #31841617)

     * InnoDB: After dropping a FULLTEXT index and renaming the
       table to move it to a new schema, the FULLTEXT auxiliary
       tables were not renamed accordingly and remained in the
       old schema directory. (Bug #31773368, Bug #100570)

     * InnoDB: After upgrading to MySQL 8.0, a failure occurred
       when attempting to perform a DML operation on a table
       that was previously defined with a full-text search
       index. (Bug #31749490)

     * InnoDB: Importing a tablespace with a page-compressed
       table did not report a schema mismatch error for source
       and destination tables defined with a different
       COMPRESSION setting. The COMPRESSION setting of the
       exported table is now saved to the .cfg metadata file
       during the FLUSH TABLES ... FOR EXPORT operation, and
       that information is checked on import to ensure that both
       tables are defined with the same COMPRESSION setting.
       (Bug #31744694)

     * InnoDB: Dummy keys used to check if the MySQL Keyring
       plugin is functioning were left behind in an inactive
       state, and the number of inactive dummy keys increased
       over time. The actual master key is now used instead, if
       present. If no master key is available, a dummy master
       key is generated. (Bug #31737924)

     * InnoDB: Querying the INFORMATION_SCHEMA.FILES table after
       moving the InnoDB system tablespace outside of the data
       directory raised a warning indicating that the
       innodb_system filename is unknown. (Bug #31603047)

     * InnoDB: In a replication scenario involving a replica
       with binary logging or log_slave_updates disabled, the
       server failed to start due to an excessive number of gaps
       in the mysql.gtid_executed table. The gaps occurred for
       workloads that included both InnoDB and non-InnoDB
       transactions. GTIDs for InnoDB transactions are flushed
       to the mysql.gtid_executed table by the GTID persister
       thread, which runs periodically, while GTIDs for
       non-InnoDB transactions are written to the to the
       mysql.gtid_executed table directly by replica server
       threads. The GTID persister thread fell behind as it
       cycled through merging entries and compressing the
       mysql.gtid_executed table. As a result, the size of the
       GTID flush list for InnoDB transactions grew over time
       along with the number of gaps in the mysql.gtid_executed
       table, eventually causing a server failure and subsequent
       startup failures. To address this issue, the GTID
       persister thread now writes GTIDs for both InnoDB and
       non-InnoDB transactions, and foreground commits are
       forced to wait if the GTID persister thread falls behind.
       Also, the gtid_executed_compression_period default
       setting was changed from 1000 to 0 to disabled explicit
       compression of the mysql.gtid_executed table by default.
       Thanks to Venkatesh Prasad for the contribution. (Bug
       #31599938, Bug #100118)

     * InnoDB: Persisting GTID values for XA transactions
       affected XA transaction performance. Two GTID values are
       generated for XA transactions, one for the prepare stage
       and another for the commit stage. The first GTID value is
       written to the undo log and later overwritten by the
       second GTID value. Writing of the second GTID value could
       only occur after flushing the first GTID value to the
       gtid_executed table. Space is now reserved in the undo
       log for both XA transaction GTID values. (Bug #31467953,
       Bug #99638)

     * InnoDB: InnoDB source files were updated to address
       warnings produced when building Doxygen source code
       documentation. (Bug #31354760)

     * InnoDB: The full-text search synchronization thread
       attempted to read a previously-freed word from the index
       cache. (Bug #31310404)

     * InnoDB: A 20µs sleep in the buf_wait_for_read() function
       introduced with parallel read functionality in MySQL
       8.0.17 took 1ms on Windows, causing an unexpected timeout
       when running certain tests. Also, AIO threads were found
       to have uneven amounts of waiting operating system IO
       requests. (Bug #31095274)
       References: This issue is a regression of: Bug #31123564.

     * InnoDB: Cleanup in certain replicated XA transactions
       failed to reattach transaction object (trx_t), which
       raised an assertion failure. (Bug #31006095)

     * InnoDB: An interrupted tablespace encryption operation
       did not update the encrypt_type table option information
       in the data dictionary when the operation resume
       processing after the server was restarted. (Bug
       #30883833, Bug #98537, Bug #30883833, Bug #98537, Bug
       #30888919, Bug #98564)

     * InnoDB: The tablespace encryption type setting was not
       properly updated due to a failure during the resumption
       of an ALTER TABLESPACE ENCRYPTION operation following a
       server failure. (Bug #30883833, Bug #98537)

     * InnoDB: Internal counter variables associated with thread
       sleep delay and threads entering an leaving InnoDB were
       revised to use C++ std::atomic. Built-in atomic
       operations were removed. Thanks to Yibo Cai from ARM for
       the contribution. (Bug #30567060, Bug #97704)

     * InnoDB: A relaxed memory order was implemented for
       dictionary memory variable fetch-add
       (dict_temp_file_num.fetch_add) and store
       (dict_temp_file_num.store) operations.
       Thanks to Yibo Cai for the contribution. (Bug #30567054,
       Bug #97703)

     * InnoDB: A background thread that resumed a tablespace
       encryption operation after the server started failed to
       take an metadata lock on the tablespace, which permitted
       concurrent DDL operations and led to a race condition
       with the startup thread. The startup thread now waits
       until the tablespace metadata lock is taken. (Bug
       #28531637)

     * InnoDB: Calls to numa_all_nodes_ptr were replaced by the
       numa_get_mems_allowed() function. Thanks to Daniel Black
       for the contribution. (Bug #24693086, Bug #83044)

     * Partitioning: ALTER TABLE t1 EXCHANGE PARTITION ... WITH
       TABLE t2 led to an assert when t1 was not a partitioned
       table. (Bug #100971, Bug #31941543)
       References: This issue is a regression of: Bug #29706669.

     * Replication: The network_namespace parameter for the
       asynchronous_connection_failover_add_source() and
       asynchronous_connection_failover_delete_source() UDFs is
       no longer used from MySQL 8.0.23. These UDFs add and
       remove replication source servers from the source list
       for a replication channel for the asynchronous connection
       failover mechanism. The network namespace for a
       replication channel is managed using the CHANGE
       REPLICATION SOURCE statement, and has special
       requirements for Group Replication source servers, so it
       should no longer be specified in the UDFs. (Bug
       #32078189)

     * Replication: When the system variable
       transaction_write_set_extraction=XXHASH64 is set, which
       is the default in MySQL 8.0 and a requirement for Group
       Replication, the collection of writes for a transaction
       previously had no upper size limit. Now, for standard
       source to replica replication, the numeric limit on write
       sets specified by
       binlog_transaction_dependency_history_size is applied,
       after which the write set information is discarded but
       the transaction continues to execute. Because the write
       set information is then unavailable for the dependency
       calculation, the transaction is marked as non-concurrent,
       and is processed sequentially on the replica. For Group
       Replication, the process of extracting the writes from a
       transaction is required for conflict detection and
       certification on all group members, so the write set
       information cannot be discarded if the transaction is to
       complete. The byte limit set by
       group_replication_transaction_size_limit is applied
       instead of the numeric limit, and if the limit is
       exceeded, the transaction fails to execute. (Bug
       #32019842)

     * Replication: When mysqlbinlog's --print-table-metadata
       option was used, mysqlbinlog used a different method for
       assessing numeric fields to the method used by the server
       when writing to the binary log, resulting in incorrect
       metadata output relating to these fields. mysqlbinlog now
       uses the same method as the server. (Bug #31956206)

     * Replication: When using network namespaces in a
       replication channel and the initial connection from the
       replica to the master was interrupted, subsequent
       connection attempts failed to use the correct namespace
       information. (Bug #31954087)

     * Replication: If the Group Replication applier channel
       (group_replication_applier) was holding a lock on a
       table, for example because of a backup in progress, and
       the member was expelled from the group and tried to
       rejoin automatically, the auto-rejoin attempt was
       unsuccessful and did not retry. Now, Group Replication
       checks during startup and rejoin attempts whether the
       group_replication_applier channel is already running. If
       that is the case at startup, an error message is
       returned. If that is the case during an auto-rejoin
       attempt, that attempt fails, but further attempts are
       made as specified by the
       group_replication_autorejoin_tries system variable. (Bug
       #31648211)

     * Replication: If a group member was expelled and made an
       auto-rejoin attempt at a point when some tables on the
       instance were locked (for example while a backup was
       running), the attempt failed and no further attempts were
       made. This scenario is now handled correctly. (Bug
       #31460690)

     * Replication: As the number of replicas replicating from a
       semisynchronous source server increased, locking
       contention could result in a performance degradation. The
       locking mechanisms used by the plugins have been changed
       to use shared locks where possible, avoid unnecessary
       lock acquisitions, and limit callbacks. The new behaviors
       can be implemented by enabling the following system
       variables:

          + replication_sender_observe_commit_only=1 limits
            callbacks.

          + replication_optimize_for_static_plugin_config=1 adds
            shared locks and avoids unnecessary lock
            acquisitions. This system variable must be disabled
            if you want to uninstall the plugin.
       Both system variables can be enabled before or after
       installing the semisynchronous replication plugin, and
       can be enabled while replication is running.
       Semisynchronous replication source servers can also get
       performance benefits from enabling these system
       variables, because they use the same locking mechanisms
       as the replicas. (Bug #30519928)

     * Replication: On a multi-threaded replica where the commit
       order is preserved, worker threads must wait for all
       transactions that occur earlier in the relay log to
       commit before committing their own transactions. If a
       deadlock occurs because a thread waiting to commit a
       transaction later in the commit order has locked rows
       needed by a transaction earlier in the commit order, a
       deadlock detection algorithm signals the waiting thread
       to roll back its transaction. Previously, if transaction
       retries were not available, the worker thread that rolled
       back its transaction would exit immediately without
       signalling other worker threads in the commit order,
       which could stall replication. A worker thread in this
       situation now waits for its turn to call the rollback
       function, which means it signals the other threads
       correctly. (Bug #26883680, Bug #87796)

     * Replication: GTIDs are only available on a server
       instance up to the number of non-negative values for a
       signed 64-bit integer (2 to the power of 63 minus 1). If
       you set the value of gtid_purged to a number that
       approaches this limit, subsequent commits can cause the
       server to run out of GTIDs and take the action specified
       by binlog_error_action. From MySQL 8.0.23, a warning
       message is issued when the server instance is approaching
       the limit. (Bug #26035544)

     * Microsoft Windows: On Windows, running the MySQL server
       as a service caused shared-memory connections to fail.
       (Bug #32009251)

     * JSON: JSON_ARRAYAGG() did not always perform proper error
       handling. (Bug #31856260, Bug #32012559, Bug #32181438)

     * JSON: When updating a JSON value using JSON_SET(),
       JSON_REPLACE(), or JSON_REMOVE(), the target column can
       sometimes be updated in-place. This happened only when
       the target table of the update operation was a base
       table, but when the target table was an updatable view,
       the update was always performed by writing the full JSON
       value.
       Now in such cases, an in-place update (that is, a partial
       update) is also performed when the target table is an
       updatable view. (Bug #25840784)

     * JSON: Work done in MySQL 8.0.22 to cause prepared
       statements to be prepared only once introduced a
       regression in the handling of dynamic parameters to JSON
       functions. All JSON arguments were classified as data
       type MYSQL_TYPE_JSON, which overlooked the fact that JSON
       functions take two kinds of JSON parameters---JSON values
       and JSON documents---and this distinction cannot be made
       with the data type only. For Bug #31667405, this problem
       was solved for comparison operators and the IN() operator
       by making it possible to tag a JSON argument as being a
       scalar value, while letting arguments to other JSON
       functions be treated as JSON documents.
       The present fix restores for a number of JSON functions
       their treatment of certain arguments as JSON values, as
       listed here:
       The first argument to MEMBER OF()
       The third, fifth, seventh, and subsequent odd-numbered
       arguments to the functions JSON_INSERT(), JSON_REPLACE(),
       JSON_SET(), JSON_ARRAY_APPEND(), and JSON_ARRAY_INSERT().
       (Bug #101284, Bug #32063203)
       References: See also: Bug #31667405.

     * JSON: When mysqld was run with --debug, attempting to
       execute a query that made use of a multi-valued index
       raised an error. (Bug #99833, Bug #31474182)

     * Use of the thread_pool plugin could result in Address
       Sanitizer warnings. (Bug #32213294)

     * While pushing a condition down to a materialized derived
       table, and a condition is partially pushed down, the
       optimizer may, in some cases in which a query
       transformation has added new conditions to the WHERE
       condition, call the internal fix_fields() function for
       the condition that remains in the outer query block. A
       successful return from this function call was
       misinterpreted as an error, leading to the silent failure
       of the original statement. (Bug #32150145)

     * Multiple calls to a stored procedure containing an ALTER
       TABLE statement that included an ORDER BY clause could
       cause a server exit. (Bug #32147402)

     * Prepared statements involving stored programs could cause
       heap-use-after-free memory problems. (Bug #32131022, Bug
       #32045681, Bug #32051928)

     * Queries on INFORMATION_SCHEMA tables that involved
       materialized derived tables could fail. (Bug #32127562,
       Bug #101504)

     * A potential buffer overflow was fixed. Thanks to Sifang
       Zhao for pointing out the issue, and for suggesting a fix
       (although it was not used). (Bug #32113015, Bug #101448)

     * Conversion of FLOAT values to values of type INT could
       generate Undefined Behavior Sanitizer warnings. (Bug
       #32099994, Bug #32100033)

     * In multiple-row queries, the LOAD_FILE() function
       evaluated to the same value for every row. (Bug
       #32096341, Bug #101401)

     * Generic Linux tar file distributions had too-restrictive
       file permissions after unpacking, requiring a manual
       chmod to correct. (Bug #32080900)

     * For debug builds, prepared SET statements containing
       subqueries in stored procedures could raise an assertion.
       (Bug #32078387)
       References: See also: Bug #32100210.

     * For prepared statements, illegal mix of collations errors
       could occur for legal collation mixes. (Bug #32077842,
       Bug #101346, Bug #32145078, Bug #101575)

     * The functions REGEXP_LIKE(), REGEXP_INSTR(), and
       REGEXP_REPLACE() raise errors for malformed regular
       expression patterns, but could also return NULL for such
       cases, causing subsequent debug asserts. Now we ensure
       that these functions do not return NULL except in certain
       specified cases.
       The function REGEXP_SUBSTR() can always return NULL, so
       no such check is needed, and for this function we make
       sure that one is not performed. (Bug #32053093)

     * Testing an aggregate function for IS NULL or IS NOT NULL
       in a HAVING condition using WITH ROLLUP led to wrong
       results. (Bug #32049313)

     * When a new aggregate function was added to the current
       query block because an inner query block had an aggregate
       function requiring evaluation in the current one, the
       server did not add rollup wrappers to it as needed. (Bug
       #32034914)

     * For debug builds, certain CREATE TABLE statements with
       CHECK constraints could raise an assertion. (Bug
       #32018406, Bug #101180)

     * Incorrect BLOB field values were passed from InnoDB
       during a secondary engine load operation. (Bug #32014483)

     * The LOCK_ORDER tool did not correctly represent InnoDB
       share exclusive locks. (Bug #31994052)

     * The server did not handle properly an error raised when
       trying to use an aggregation function with an invalid
       column type as part of a hash join. (Bug #31989333)

     * The length of the WORD column of the
       INFORMATION_SCHEMA.KEYWORDS table could change depending
       on table contents. (Bug #31982157)

     * The Performance Schema host_cache table was empty and did
       not expose the contents of the host cache if the
       Performance Schema was disabled. The table now shows
       cache contents regardless of whether the Performance
       Schema is enabled. (Bug #31978763)

     * A HANDLER READ statement sometimes hit an assert when a
       previous statement did not restore the original value of
       THD::mark_used_columns after use. (Bug #31977414)

     * Importing a compressed table could cause an unexpected
       server exit if the table contained values that were very
       large when uncompressed. (Bug #31943021)

     * Removed a memory leak that could occur when a subquery
       using a hash join and LIMIT was executed repeatedly. (Bug
       #31940549)

     * A compilation failure on Ubuntu was corrected. (Bug
       #31930934, Bug #100938)

     * Memory used for storing partial-revokes information could
       grow excessively for sessions that executed a large
       number of statements. (Bug #31919448)

     * The server did not handle all cases of the
       WHERE_CONDITION optimization correctly. (Bug #31905199)

     * FLUSH TABLES WITH READ LOCK could block other sessions
       from executing SHOW TABLE STATUS. (Bug #31894662)

     * In some cases, MIN() and MAX() incorrectly returned NULL
       when used as window functions with temporal or JSON
       values as arguments. (Bug #31882291)

     * GRANT ... GRANT OPTION ... TO and GRANT ... TO .. WITH
       GRANT OPTION sometimes were not correctly written to the
       server logs. (Bug #31869146, Bug #100793)

     * For debug builds, CREATE TABLE using a partition list of
       more than 256 entries raised an assertion. (Bug
       #31867653)

     * It was possible for queries in the file named by the
       init_file system variable to cause server startup
       failure. (Bug #31835782)

     * When performing a hash join, the optimizer could register
       a false match between a negative integer value and a very
       large unsigned integer value. (Bug #31832001, Bug
       #31940639, Bug #100967)

     * SHOW VARIABLES could report an incorrect value for the
       partial_revokes system variable. (Bug #31819558, Bug
       #100677)

     * In the Performance Schema user_defined_functions table,
       the value of the UDF_LIBRARY column is supposed to be
       NULL for UDFs registered via the service API. The value
       was incorrectly set to the empty string. (Bug #31791754)

     * The server automatic upgrade procedure failed to upgrade
       older help tables that used the latin1 character set.
       (Bug #31789964)

     * Duplicate warnings could occur when executing an SQL
       statement that read the grant tables in serializable or
       repeatable-read transaction isolation level. (Bug
       #31769242)

     * In certain queries with DISTINCT aggregates (which in
       general are solved by sorting before aggregation), the
       server used a temporary table instead of streaming due to
       the mistaken assumption that the logic for handling the
       temporary table performed deduplication. Now the server
       checks for the implied unique index instead, which is
       more robust and allows for the removal of unnecessary
       logic. (Bug #31762806)

     * Certain combinations of lower_case_table_names values and
       schema names in Event Scheduler event definitions could
       cause the server to stall. (Bug #31733090)

     * Calling one stored function from within another could
       produce a conflict in field resolution, resulting in a
       server exit. (Bug #31731334)

     * User-defined functions defined without a udf_init()
       method could cause an unexpected server exit. (Bug
       #31701219)

     * Setting the secure_file_priv system variable to NULL
       should disable its action, but instead caused the server
       to create a directory named NULL. (Bug #31700734, Bug
       #100384)

     * mysqlpump could exit unexpectedly due to improper
       simultaneous accesses to shared structures. (Bug
       #31696241)

     * Uninstalling a component and deregistering user-defined
       functions (UDFs) installed by the component was not
       properly synchronized with whether the UDFs were
       currently in use. (Bug #31646698)

     * Cleanup following execution of a prepared statement that
       performed a multi-table UPDATE or DELETE was not always
       done correctly, which meant that, following the first
       execution of such a prepared statement, the server
       reported a nonzero number of rows updated, even though no
       rows were actually changed. (Bug #31640267)
       References: See also: Bug #32100210.

     * For the engines which support primary key extension, when
       the total key length exceeded MAX_KEY_LENGTH or the
       number of key parts exceeded MAX_REF_PARTS, key parts of
       primary keys which did not fit within these limits were
       not added to the secondary key, but key parts of primary
       keys were unconditionally marked as part of secondary
       keys.
       This led to a situation in which the secondary key was
       treated as a covering index, which meant sometimes the
       wrong access method was chosen.
       This is fixed by modifying the way in which key parts of
       primary keys are added to secondary keys so that those
       which do not fit within which do not fit within the
       limits mentioned previously mentioned are cleared. (Bug
       #31617858)

     * When MySQL is configured with -DWITH_ICU=system, CMake
       now checks that the ICU library version is sufficiently
       recent. (Bug #31600044)

     * Enabling DISABLE_PSI_xxx Performance Schema-related CMake
       options caused build failures. (Bug #31549724)

     * When invoked with the --binary-as-hex option, mysql
       displayed NULL values as empty binary strings (0x).
       Selecting an undefined variable returned the empty binary
       string (0x) rather than NULL. (Bug #31549724, Bug
       #31638968, Bug #100251)

     * Some queries returned different results depending on the
       value of internal_tmp_mem_storage_engine.
       The root cause of this issue related to the fact that,
       when buffering rows for window functions, if the size of
       the in-memory temporary table holding these buffered rows
       exceeds the limit specified, a new temporary table is
       created on disk; the frame buffer partition offset is set
       at the beginning of a new partition to the total number
       of rows that have been read so far, and is updated
       specifically for use when the temporary table is moved to
       disk (this being used to calculate the hints required to
       process window functions). The problem arose because the
       frame buffer partition offset was not updated for the
       specific case when a new partition started while creating
       the temporary table on disk, which caused the wrong rows
       to be read.
       This issue is fixed by making sure to update the frame
       buffer partition offset correctly whenever a new
       partition starts while a temporary table is moved to
       disk. (Bug #31546816)

     * While buffering rows for window functions, if the size of
       the in-memory temporary table holding these buffered rows
       exceeds the limit specified by temptable_max_ram, a new
       temporary table is created on disk. After the creation of
       the temporary table, hints used to process window
       functions need to be reset, since the temporary table is
       now moved to disk, making the existing hints unusable.
       When the creation of the temporary table on disk occurred
       when the first row in the frame buffer was being
       processed, the hints had not been initialized and trying
       to reset these uninitialized hints resulted in an
       unplanned server exit.
       This issue is fixed by adding a check to verify whether
       frame buffer hints have been initialized, prior to
       resetting them. (Bug #31544404)

     * The Performance Schema could produce incorrect results
       for joins on a CHANNEL_NAME column when the index for
       CHANNEL_NAME was disabled with USE INDEX (). (Bug
       #31544023, Bug #99989)

     * When removing unused window definitions, a subquery that
       was part of an ORDER BY was not removed. (Bug #31518806)

     * In certain cases, the server did not handle
       multiply-nested subqueries correctly. (Bug #31472704)

     * The recognized syntax for a VALUES statement includes an
       ORDER BY clause, but this clause was not resolved, so the
       execution engine could encounter invalid data. (Bug
       #31387510)

     * The server attempted to access a non-existent temporary
       directory at startup, causing a failure. Checks were
       added to ensure that temporary directories exist, and
       that files are successfully created in the tmpdir
       directory. (Bug #31377118)

     * While removing redundant sorting, a window's ordering was
       removed due to the fact that rows were expected to come
       in order because of the ordering of another window. When
       the other window was subsequently removed because it was
       unused, this resulted in unordered rows, which was not
       expected during evaluation.
       Now in such cases, removal of redundant sorts is not
       performed until after any unused windows have been
       removed. In addition, resolution of any rollups has been
       moved to the preparation phase. (Bug #31361393)

     * Semisynchronous replication errors were incorrectly
       written to the error log with a subsystem tag of Server.
       They are now written with a tag of Repl, the same as for
       other replication errors. (Bug #31327337)

     * A user could grant itself as a role to itself. (Bug
       #31222230)

     * The server did not always correctly handle cases in which
       multiple WHERE conditions, one of which was always FALSE,
       referred to the same subquery. (Bug #31216115)

     * With a lower_case_table_names=2 setting, InnoDB
       background threads sometimes acquired table metadata
       locks using the wrong character case for the schema name
       part of a lock key, resulting in unprotected metadata and
       race conditions. The correct character case is now
       applied. Changes were also implemented to prevent
       metadata locks from being released before corresponding
       data dictionary objects, and to improve assertion code
       that checks lock protection when acquiring data
       dictionary objects. (Bug #31165802)

     * If a CR_UNKNOWN_ERROR was to be sent to a client, an
       exception occurred. (Bug #31123643)

     * Conversion of DOUBLE values to values of type BIT, ENUM,
       or SET could generate Undefined Behavior Sanitizer
       warnings. (Bug #31019130)

     * Certain accounts could cause server startup failure if
       the --skip-name-resolve option was enabled. (Bug
       #31018510)

     * Client programs could unexpectedly exit if communication
       packets contained bad data. (Bug #30890850)

     * A buffer overflow in the client library was fixed. (Bug
       #30885987)

     * When creating a multi-valued or other functional index, a
       performance drop was seen when executing a query against
       the table on which the index was defined, even though the
       index itself was not actually used. This occurred because
       the hidden virtual column that backs such indexes was
       evaluated unnecessarily for each row in the query. (Bug
       #30838749)
       References: This issue is a regression of: Bug #28069731.

     * CMake checks for libcurl dependencies were improved. (Bug
       #30268245)

     * mysql_config_editor incorrectly treated # in password
       values as a comment character. (Bug #29861961, Bug
       #95597)

     * In some cases, the optimizer attempted to compute the
       hash value for an empty string. Now a fixed value is
       always used instead. (Bug #22588319)

     * The INSERT() and RPAD() functions did not correctly set
       the character set of the result. (Bug #22523946, Bug
       #79909, Bug #31887870, Bug #100841)

     * Some corner cases for val1 BETWEEEN val2 AND val3 were
       fixed, such as that -1 BETWEEN 9223372036854775808 AND 1
       returned true. (Bug #22515857, Bug #79878)

     * For the Performance Schema
       memory_summary_global_by_event_name table, the low
       watermark columns could have negative values, and the
       high watermark columns had ever-increasing values even
       when the server memory usage did not increase. (Bug
       #22246001, Bug #79285)

     * Several issues converting strings to numbers were fixed.
       (Bug #19186271, Bug #73248)

     * Certain group by queries that performed correctly did not
       return the expected result when WITH ROLLUP was added.
       This was due to the fact that decimal information was not
       always correctly piped through rollup group items,
       causing functions returning decimal values such as
       TRUNCATE() to receive data of the wrong type. (Bug
       #101684, Bug #32179240)

     * When creating fields for materializing temporary tables
       (that is, when needing to sort a join), the optimizer
       checks whether the item needs to be copied or is only a
       constant. This was not done correctly in one specific
       case; when performing an outer join against a view or
       derived table containing a constant, the item was not
       properly materialized into the table, which could yield
       spurious occurrences of NULL in the result. (Bug #101622,
       Bug #32162862)
       References: See also: Bug #31790217.

     * When REGEXP_REPLACE() was used in an SQL statement, the
       internal function Regexp_engine::Replace() did not reset
       the error code value after handling a record, which could
       affect processing of the next record, which lead to
       issues.
       Our thanks to Hope Lee for the contribution. (Bug
       #101256, Bug #32050219)

     * For a query having the following form, the column list
       sometimes assumed an inconsistent state after temporary
       tables were created, causing out-of-bounds indexing
       later:
SELECT * FROM (
    SELECT PI()
    FROM t1 AS table1, t1 AS table2
    ORDER BY PI(), table1.a
) AS d1;

       (Bug #101012, Bug #31955761, Bug #31978439)
       References: This issue is a regression of: Bug #31790217.

     * When aggregating data that was already sorted (known as
       performing streaming aggregation, due to no temporary
       tables being used), it was not possible to determine when
       a group ended until processing the first row in the next
       group, by which time the group expressions to be output
       were often already overwritten.
       This is fixed by replacing the complex logic previously
       used with the much simpler method of saving a
       representative row for the group when encountering it the
       first time, so that its columns can easily be retrieved
       for the output row when needed. (Bug #100791, Bug
       #27272052, Bug #31073167, Bug #31790217, Bug #31868610)

     * Subqueries making use of fulltext matching might not
       perform properly when subquery_to_derived was enabled,
       and could lead to an assert in debug builds. (Bug
       #100749, Bug #31851600)

     * When an ALTER TABLE ... CONVERT TO CHARACTER SET
       statement is executed, the character set of every CHAR,
       VARCHAR, and TEXT column in the table is updated to the
       new CHARACTER SET value. This change was also applied to
       the hidden CHAR column used by an ARRAY column for a
       multi-valued index; since the character set of the hidden
       column must be one of my_charset_utf8mb4_0900_bin or
       binary, this led to an assert in debug builds of the
       server.
       This issue is resolved by no longer setting the character
       set of the hidden column to that of the table when
       executing the ALTER TABLE statement referenced
       previously; this is similar to what is done for BLOB
       columns in similar circumstances. (Bug #99403, Bug
       #31301101)

     * In some cases, the server's internal string-conversion
       routines had problems handling floating-point values
       which used length specifiers and triggered use of
       scientific notation. (Bug #92537, Bug #101570, Bug
       #28691605, Bug #32144265)
       References: See also: Bug #88256, Bug #27041543.


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