tablespace ( ibtmp1 ), which did not return disk space to the operating system after temporary tables were dropped. 

The innodb_temp_tablespaces_dir  variable defines the location where session temporary tablespaces are created. The default location is the #innodb_temp  directory in the data directory. 

The INNODB_SESSION_TEMP_TABLESPACES  table provides metadata about session temporary tablespaces. 

The global temporary tablespace ( ibtmp1 ) now stores rollback segments for changes made to user- created temporary tables. 

•As of MySQL 8.0.14, InnoDB  supports parallel clustered index reads, which can improve CHECK TABLE  performance. This feature does not apply to secondary index scans. The innodb_parallel_read_threads  session variable must be set to a value greater than 1 for parallel clustered index reads to occur. The default value is 4. The actual number of threads used to perform a parallel clustered index read is determined by the innodb_parallel_read_threads setting or the number of index subtrees to scan, whichever is smaller. 

•As of 8.0.14, when the innodb_dedicated_server  variable is enabled, the size and number of log files are configured according to the automatically configured buffer pool size. Previously, log file size was configured according to the amount of memory detected on the server, and the number of log files was not configured automatically. 

•As of 8.0.14, the ADD DATAFILE  clause of the CREATE TABLESPACE  statement is optional, which permits users without the FILE  privilege to create tablespaces. A CREATE TABLESPACE  statement executed without an ADD DATAFILE  clause implicitly creates a tablespace data file with a unique file name. 

•By default, when the amount of memory occupied by the TempTable storage engine exceeds the memory limit defined by the temptable_max_ram  variable, the TempTable storage engine begins allocating memory-mapped temporary files from disk. As of MySQL 8.0.16, this behavior is controlled by the temptable_use_mmap  variable. Disabling temptable_use_mmap  causes the TempTable storage engine to use InnoDB  on-disk internal temporary tables instead of memory-mapped files as its overflow mechanism. For more information, see Internal Temporary Table Storage Engine. 

•As of MySQL 8.0.16, the InnoDB  data-at-rest encryption feature supports encryption of the mysql system tablespace. The mysql  system tablespace contains the mysql  system database and the MySQL data dictionary tables. For more information, see Section 15.13, “InnoDB Data-at-Rest Encryption” . 

•The innodb_spin_wait_pause_multiplier  variable, introduced in MySQL 8.0.16, provides greater control over the duration of spin-lock polling delays that occur when a thread waits to acquire a mutex or rw-lock. Delays can be tuned more finely to account for differences in PAUSE instruction 

