I have a Set named 'Projects' with many key-value pairs and I want to retrieve one of the values by providing its key. I checked the redis doc but I only found how to retrieve the entire Set. Is it possible to just retrieve one value by providing its key?
Your concept of Set does not match Redis'.
All members of a set in Redis are stored in a single key. Therefore you can't access members individually by a key.
You should use hashes: http://www.redis.io/commands#hash
HSET key field value does what you are looking for.
Related
If two distinct keys have the same value (and say the value is large) does redis store the value twice or will it use a pointer / reference. The way git does ?
Redis stores them as two independent key-value pairs.
If you want to remove the duplication, you have to build an index from multiple keys to a shared value by yourself.
What's the practical difference between keeping data in multiple hashes (HSET foo oof 1, HSET bar rab 2) and using plain keys in a hierarchy (SET foo:oof 1, SET bar:rab 2)?
According to the manual, you'd use hashes to represent a single object.
Also, it's not that efficient to iterate over Redis keys, so if you need to get all the data from a single object, HGETALL is your friend, not a KEYS thing:10:*/multiget fiasco.
However, you can't e.g. set expiry for only one key of a hash, so if you need that functionality, you'll want to use regular keys.
We are storing path's to data in redis as following:
KEY: `/pathOfUniqueAsset/v11/`
VALUE: `/disk1/pathOfUniqueAsset/path/v/11/`.
As you can see, the v which stands for version, will grow over time. I was wondering if there is a way to store flavors/versions of a key/value pair?
You can use a Hash instead of a String, as the key's value type. In the Hash, you can have a field per version/flavor and have the value as the associated path.
E.g.:
HSET /pathOfUniqueAsset v11 /disk1/pathOfUniqueAsset/path/v/11/
What are you trying to achieve? Do you need to keep older versions? If not, overwrite the key. If yes, what would 'version' of the key give you? You already know your version from the key. If you arrange your keys as pathOfUniqueAsset.v11, you can later issue KEYS pathOfUniqueAsset.* (or better SCAN) to get all versions. This way you can set EXPIRE individually. If you'll use HSET like #ItamarHaber suggests you can only delete values manually, but iterating a set is much faster than KEYS lookup (EDIT: actually, it depends on some factors, mostly the amount of other keys).
If you instead want a list of assets for each version kept together, you can use dedicated set of all keys associated to this version. Like
SET /pathOfUniqueAsset/v1 ...
HSET assets.v1 pathOfUniqueAsset /pathOfUniqueAsset/v1
I am storing objects as hash ,for example: key-> customer:123 ,email->dk#gmail.com,mobile->828212,name->darshan etc...
Now is it possible in redis to query customers based on email without storing the cross relationship as set which is more of a workaround.
like for example,at the time of insertion of customer storing Set as key->email:dk#gmail.com value->customer:123 and so on.
Lets say if I have 100 fields in a hash, and i need to query 20 of them(like email)
it increases the count of keys in redis instance significantly if we create each entry of those fields in Sets as well.
Is there any other alternative or better approach?
Redis doesn't have inbuilt indexing/searching by fields because it is not a database but more like a data structures server(each key holds a data structure like set/list/map/sortedset/number of unique values etc), but if you are using redis 4.0 you can use the search module to accomplish it. The link is here.
I am still new to Redis and wondering if it would be possible to have a HASH of LIST.
Then I could do for example LPOP HASH myKey where the hash set holds each list's key and the lists contains data that I want to manipulate.
Redis does not provide nested data structures, therefore a List of Hashes isn't possible. A Redis List can only contain strings, but what you could do is store the Hashes' key names in a List and do HGET after popping.