modifies secondary index pages, or when there are lots of secondary indexes that are regularly changed by DML activity. 

A.16.9. When should the change buffer not be used? 

You might consider disabling the change buffer if the entire data set fits within the InnoDB  buffer pool, if you have relatively few secondary indexes, or if you are using solid-state storage, where random reads are about as fast as sequential reads. Before making configuration changes, it is recommended that you run tests using a representative workload to determine if disabling the change buffer provides any benefit. 

A.16.10. Where can I find additional information about the change buffer? 

See Section 15.5.2, “Change Buffer” . 

## A.17 MySQL 8.0 FAQ: InnoDB Data-at-Rest Encryption 

A.17.1 Is data decrypted for users who are authorized to see it? .................................................... 5277 

A.17.2 What is the overhead associated with InnoDB  data-at-rest encryption? ................................ 5277 

A.17.3 What are the encryption algorithms used with InnoDB  data-at-rest encryption? ..................... 5277 

A.17.4 Is it possible to use 3rd party encryption algorithms in place of the one provided by the InnoDB  data-at-rest encryption feature? .............................................................................. 5277 

A.17.5 Can indexed columns be encrypted? .................................................................................. 5278 

A.17.6 What data types and data lengths does InnoDB  data-at-rest encryption support? .................. 5278 

A.17.7 Does data remain encrypted on the network? ..................................................................... 5278 

A.17.8 Does database memory contain cleartext or encrypted data? ............................................... 5278 

A.17.9 How do I know which data to encrypt? ............................................................................... 5278 

A.17.10 How is InnoDB  data-at-rest encryption different from encryption functions MySQL already provides? ............................................................................................................................ 5278 

A.17.11 Does the transportable tablespaces feature work with InnoDB  data-at-rest encryption? ........ 5278 

A.17.12 Does compression work with InnoDB  data-at-rest encryption? ........................................... 5278 

A.17.13 Can I use mysqlpump  or mysqldump  with encrypted tables? ............................................ 5278 

A.17.14 How do I change (rotate, re-key) the master encryption key? ............................................. 5279 

A.17.15 How do I migrate data from a cleartext InnoDB  tablespace to an encrypted InnoDB tablespace? ........................................................................................................................ 5279 

A.17.1. Is data decrypted for users who are authorized to see it? 

Yes. InnoDB  data-at-rest encryption is designed to transparently apply encryption within the database without impacting existing applications. Returning data in encrypted format would break most existing applications. InnoDB  data-at-rest encryption provides the benefit of encryption without the overhead associated with traditional database encryption solutions, which would typically require expensive and substantial changes to applications, database triggers, and views. 

A.17.2. What is the overhead associated with InnoDB  data-at-rest encryption? 

There is no additional storage overhead. According to internal benchmarks, performance overhead amounts to a single digit percentage difference. 

A.17.3. What are the encryption algorithms used with InnoDB  data-at-rest encryption? 

InnoDB  data-at-rest encryption supports the Advanced Encryption Standard (AES256) block-based encryption algorithm. It uses Electronic Codebook (ECB) block encryption mode for tablespace key encryption and Cipher Block Chaining (CBC) block encryption mode for data encryption. 

A.17.4. Is it possible to use 3rd party encryption algorithms in place of the one provided by the InnoDB data-at-rest encryption feature? 

