MySQL 8.4 Release Notes
在以前的 MySQL 版本中，字典数据部分存储在元数据文件中。基于文件的元数据存储存在的问题包括昂贵的文件扫描、易受文件系统相关错误影响、处理复制和崩溃恢复失败状态的复杂代码，以及缺乏可扩展性，使得很难为新功能和关系对象添加元数据。In previous MySQL releases, dictionary data was partially stored in metadata files. Issues with file-based metadata storage included expensive file scans, susceptibility to file system-related bugs, complex code for handling of replication and crash recovery failure states, and a lack of extensibility that made it difficult to add metadata for new features and relational objects.
以下列出的元数据文件已从 MySQL 中删除。除非另有说明，之前存储在元数据文件中的数据现在存储在数据字典表中。The metadata files listed below are removed from MySQL. Unless otherwise noted, data previously stored in metadata files is now stored in data dictionary tables.
.frm文件：表元数据文件。移除.frm文件后：.frmfiles: Table metadata files. With the removal of.frmfiles:.frm文件结构强加的 64KB 表定义大小限制已被移除。The 64KB table definition size limit imposed by the.frmfile structure is removed.信息模式
TABLES表的VERSION列报告硬编码值10，这是 MySQL 5.7 中使用的最后一个.frm文件版本。The Information SchemaTABLEStable'sVERSIONcolumn reports a hardcoded value of10, which is the last.frmfile version used in MySQL 5.7.
.par文件：分区定义文件。InnoDB在 MySQL 5.7 中引入对InnoDB表的原生分区支持后，停止使用分区定义文件。.parfiles: Partition definition files.InnoDBstopped using partition definition files in MySQL 5.7 with the introduction of native partitioning support forInnoDBtables..TRN文件：触发器命名空间文件。.TRNfiles: Trigger namespace files..TRG文件：触发器参数文件。.TRGfiles: Trigger parameter files..isl文件：InnoDB符号链接文件，包含在数据目录之外创建的单表文件表空间文件的位置。.islfiles:InnoDBSymbolic Link files containing the location of file-per-table tablespace files created outside of the data directory.db.opt文件：数据库配置文件。每个数据库目录一个文件，包含数据库默认字符集属性。db.optfiles: Database configuration files. These files, one per database directory, contained database default character set attributes.ddl_log.log文件：该文件包含由数据定义语句生成的元数据操作记录，例如DROP TABLE和ALTER TABLE。ddl_log.logfile: The file contained records of metadata operations generated by data definition statements such asDROP TABLEandALTER TABLE.