The InnoDB data dictionary is comprised of internal system tables that contain metadata used to keep track of objects such as tables, indexes, and table columns. The metadata is physically located in the InnoDB system tablespace. For historical reasons, data dictionary metadata overlaps to some degree with information stored in InnoDB table metadata files (.frm files).
InnoDB數據字典由內部系統表組成，這些表包含用於跟蹤對象的元數據,例如表，索引，列。元數據是存放在innodb系統表空間的物理位置上的，由於歷史的原因，數據字典元數據一定程度上與存儲在InnoDB表的元數據文件的信息有重疊
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