What is Unzip_LRU list?

Question

I am learning mysql buffer pool.

I know that buffer pools have lru list and unzip lru list in the InnoDB storage engine.

I don't know why InnoDB buffer pool use the unzip lru list.

Why use unzip lru list and when?

Answer 1

To operate and search on data the page has to be uncompressed. The notion of compressed started with ROW_FORMAT=COMPRESSED tables. When ordinary pages are uncompress too they use use the same list.