Complex data structures Redis

What would the 'usual' way to store such a data structure (or would you not?)

For example harry and sally would be stored each in separate hashes where fields would represent their properties like age and weight. Then set structure would hold all the members (harry, sally, ...) which you have stored in redis.

Would you be able to directly get a value (e.g. get harry : age ?)

Yes, see HGET or HMGET or HGETALL.

Once stored could you directly change the value of a sub key (e.g. sally : weight = 100)

Yes, see HSET.

Lets take a complex data that we have to store in redis , for example this one:

  $data = { 
            "user:1"  : {
                       name : "sally",
                       password : "123"
                       logs : "25th october" "30th october" "12 sept",
                       friends : "34" , "24", "10"
                   } 
            "user:2"  :{
                       name : ""
                       password : "4567"
                       logs :
                       friends: ""
                   }
          }

The problem that we face is that the friends & logs are lists. So what we can do to represent this data in redis is use hashes and lists something like this :

Option 1. A hash map with keys as user:1 and user:2

      hmset user:1 name "sally" password "12344"
      hmset user:2 name "pally" password "232342"
      create separate list of logs as 
              logs:1 { here 1 is the user id }
              lpush logs:1 "" "" "" 
              lpush logs:2 "" "" ""
      and similarly for friends.

Option 2: A hash map with dumped json data as string encode

      hmset user:1 name "sally" password "12344" logs "String_dumped_data" friends "string of dumped data"

Option 3: This is another representation of #1

      something like user:1:friends -> as a list 
      and            user:2:friends -> as a list 

Please , correct me if i m wrong.

Depends on what you want to do, but if your datastructure is not deeper nested and you need access to each field, I would recommend using hashes: http://redis.io/commands#hash

Here is a good overview over the redis datatypes, each with pro and contra: http://redis.io/topics/data-types