Memory occupied by individual key in Redis using Jedis?

Question

How do we find memory occupied by individual key in Redis using Jedis?jedis.info("memory") provides only the total memory used by the redis server.

Abhishek · Answer 1 · 2018-11-20T04:42:36.203

After installing the redis-rdb-tools as described here, we can use it to find out the memory used by a key.

finding out memory for a key from running redis.

redis-3.2.4 $ redis-memory-for-key -s localhost -p 6379 mystringkey
Key    "mystringkey"
Bytes    88
Type    string
redis-3.2.4 $ redis-memory-for-key -s localhost -p 6379 myhashkey
Key    "myhashkey"
Bytes    115
Type    hash
Encoding   ziplist
Number of Elements  2
Length of Largest Element 6

finding out memory for a key from a rdb file.

redis-3.2.4 $ rdb -c memory dump.rdb -k mystringkey
database,type,key,size_in_bytes,encoding,num_elements,len_largest_element

0,string,"mystringkey",88,string,13,13

finding out memory for all keys for a pattern.

redis-3.2.4 $ rdb -c memory dump.rdb -k my.*
database,type,key,size_in_bytes,encoding,num_elements,len_largest_element
0,list,"mylistkey",219,quicklist,7,6
0,sortedset,"mysortedsetkey",143,ziplist,6,5
0,hash,"myhashkey",115,ziplist,2,6
0,string,"mystringkey",88,string,13,13
0,string,"myhllkey",168,string,90,90

0,set,"mysetkey",452,hashtable,4,6

finding out memory for all keys for a pattern and exporting to a csv file.

redis-3.2.4 $ rdb -c memory dump.rdb -k my.* -f memory.csv
redis-3.2.4 $ head memory.csv 
database,type,key,size_in_bytes,encoding,num_elements,len_largest_element
0,list,"mylistkey",219,quicklist,7,6
0,sortedset,"mysortedsetkey",143,ziplist,6,5
0,hash,"myhashkey",115,ziplist,2,6
0,string,"mystringkey",88,string,13,13
0,string,"myhllkey",168,string,90,90
0,set,"mysetkey",452,hashtable,4,6

Cool, but this requires some sort of external tool, right? Perhaps adding the link to it would be good. — Itamar Haber, Nov 19 '18 at 13:37
@Abhishek thanks for the details, however I was looking for the implementation using Jedis. Please let me know if you find the solution in the direction. — Anirudha Sant, Nov 21 '18 at 05:04
@AnirudhaSant Using Jedis, solution: https://redis.io/commands/memory-usage — Abhishek, Nov 22 '18 at 05:23

score 1 · Answer 2 · answered Nov 19 '18 at 13:48

As of Redis v4, you can call the MEMORY USAGE to obtain an accurate measurement of a specific key-value.

Looking at the Jedis javadocs (http://xetorthio.github.io/jedis/), I can't find a suitable wrapper method to invoke this but you should be able to use the sendCommand() method of the Connection class to work around that.

score -1 · Answer 3 · answered May 23 '20 at 06:00

From my answer here: Is there a way to pass redis commands in jedis, without using the functions?

import redis.clients.jedis.util.SafeEncoder;
// ... Jedis setup code ...
byteSize = (Long) jedis.sendCommand(new ProtocolCommand() {
                                        @Override
                                        public byte[] getRaw() {
                                          return SafeEncoder.encode("memory");
                                        }}, 
                                    SafeEncoder.encode("usage"), 
                                    SafeEncoder.encode(key));

... please click on my original answer link above for more information about this as I'm not sure if SO would flag me if I just pasted it here completely.

Memory occupied by individual key in Redis using Jedis?

3 Answers3