Does the MySQL primary key index leaf node store the row data itself or its physical address?

such as the title.

see that MySQL generates a tree for the primary key, and the leaf node holds the row data corresponding to the primary key.

The

secondary index leaf node holds the value of the primary key.

excuse me:

does the leaf node of the primary key index hold the physical address of the row data, or the row data itself?
in the primary key index, the primary key and row data are put together. Because of this characteristic, it is called clustered index?

Mar.04,2021

different engines have different implementations
https://www.cnblogs.com/tgyco.

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