Save nested hash in redis via a node.js app

Question

I'm using node_redis and I'd like to save a structure like:

{
users : 
    "alex" : { "email" : "[email protected]",
           "password" : "alex123"},
    "sandra" : { "email" : "[email protected]",
           "password" : "sandra123"},
    ...
}

Currently, for each user I create a JSON object:

jsonObj = { "email" : "[email protected]",
            "password" : "alex123"}

and do a

db.hmset("alex", JSON.stringify(jsonObj))

Is it possible to embedded this strucute in another structure (the users one ?) How could I set users["alex"] with this structure ?

Don't you mean db.hmset("users", "alex", JSON.stringify(jsonObj)) instead of db.hmset("alex", JSON.stringify(jsonObj))??? — BMiner
– BMiner, Commented Sep 24, 2013 at 19:19
Check this answer for alternative on how to save nested data structures to Redis. — for_stack
– for_stack, Commented Sep 9, 2019 at 15:23

John Zwinck · Accepted Answer · 2011-11-29 17:46:26Z

25

As far as I know there isn't native support for nested structures in Redis, but they can be modeled for example with set+hash (similar to hierarchical trees). Hashes are probably best suited for storing fields and values of single JSON object. What I would do is to store each user with a prefix (which is a Redis convention), for example:

db.hmset("user:alex", JSON.stringify(jsonObj));

and then use sets to group users into one set with a key named users. I can then get all of the users keys by smembers command and access each of them individually with hgetall.

edited Nov 29, 2011 at 17:46

John Zwinck

252k44 gold badges347 silver badges459 bronze badges

answered Apr 18, 2011 at 11:58

yojimbo87

68.8k26 gold badges128 silver badges133 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Luc Over a year ago

thanks, this is a good approach. Then, when you need to update a particuliar user, do you "srem "users" "user:alex" and create a new set to add to users ?

yojimbo87 Over a year ago

@Luc: If the update doesn't affect his name which is used as a part of the key "user:alex" then you don't have to remove or add him again to the set. You just change specified fields in that hash and that should be all. In case when you are changing also his name you would probably have to delete the original "user:alex" hash and create new one. Then you would remove "user:alex" from "users" set and add there newly created hash key.

Luc Over a year ago

I now use this approach (mix of Hash and Set). But the update does not work by only modifying the user object retrieved. It seems we have to "hmset user:alex user" once again.

BMiner Over a year ago

I'm not sure that I understand this answer at all. You say that hashes are probably best suited for storing fields and values of a single JSON Object. Why is that better than simply just storing the JSON-encoded value to a string using SET? Are you comparing HSET user:{id} name Fred vs. SET user:{id} '{"name":"Fred"}'? If so, I'd presume that SET (and subsequent JSON parsing) is more often faster than HSET if you are frequently accessing all of the fields of the Object. Thoughts?

yojimbo87 Over a year ago

SET with JSON parsing being faster is questionable since it would probably highly depend on the string length which will be parsed and subsequently saved whereas HSET will process only required small part of the entire JSON object. If all fields are accessed SET could be a viable option and benchmarks with comparison could be interesting to see.

yojimbo87 · Accepted Answer · 2011-06-05 16:43:53Z

16

You could store the sub structure as an object and store it's id within the main structure, rather like a pointer. So, given your example, I would do the following

{
users : 
    "alex" : { "email" : "[email protected]",
           "password" : "alex123"},
    "sandra" : { "email" : "[email protected]",
           "password" : "sandra123"},
    ...
}
$x = incr idx:user
hmset user:$x email [email protected] password alex123
sadd list:user $x

$x = incr idx:user
hmset user:$x email [email protected] password sandra123
sadd list:user $x

Hope this possible solution helps

edited Jun 5, 2011 at 16:43

yojimbo87

68.8k26 gold badges128 silver badges133 bronze badges

answered Apr 27, 2011 at 9:23

Lloyd Moore

3,2081 gold badge35 silver badges32 bronze badges

1 Comment

Lloyd Moore Over a year ago

ok great. please consider a vote for the answer if it helped in any way. happy programming.

Collectives™ on Stack Overflow

Save nested hash in redis via a node.js app

2 Answers 2

5 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related