How does redis view the memory size occupied by a single key

utilize rdbtools Of redis-memory-for-key Command to view a single key Details of

official github as follows :

https://github.com/sripathikrishnan/redis-rdb-tools

Installing the tool requires python Of pip Package management , So install the environment first :

https://www.runoob.com/w3cnote/python-pip-install-usage.html

After installation , You can use redis-memory-for-key The command ,

Let's first try to see that the type is hash,hash The key is 2 Of redisObject Size occupied

s- host /ip,p- port ,d-database

bytes： Number of bytes occupied

type： Key type

encoding：redisObject The encoding format of , That is, the type of data structure that actually stores data inside

Number of Elements： Number of internal elements

Then insert another k,v. adopt bytes Subtract to get 2 How much memory does it take .

We know redis Of hash In the internal k,v Number <=512 Will use ziplist Compress the list to store data , When the number of elements is greater than 512 For each hour hashtable To store , We can do an experiment , utilize lua towards hash Insert 512 Elements ,

for i=1,512,1 do redis.call('hset', 2,i,i) end;return 1

Then let's look at the size and type of the interior

Then we insert another element

Then check the changes

Find out redis-memory-for-key The command is still relatively accurate . Besides this function ,rdbtools There are also other interesting features , Those interested can go to the official github Look around ...