How to search in redis for hash keys?

Question

I'm using hash keys to store user details like:

 hmset user:1 user_name lee  age 21
 hmset user:2 user_name david  age 25
 hmset user:3 user_name chris  age 25

I need to search for users having age = 25, name = lee. How to do a search for a specified value in a given field?

Answer 1

You cannot. Redis is a key-value store, not a relational database.

In order to search for a specific data, you need to build an access path to this data. For instance, to get the users having age = 25, you need to build an index to map the age values to users. It can be done with a set. This is the same for the name.

Once you have sets for age and name, you can search users by intersecting the sets. For example:

# Add 3 users
hmset user:1 user_name lee age 21
hmset user:2 user_name david age 25
hmset user:3 user_name chris age 25

# Maintain age index
sadd age:21 1
sadd age:25 2 3

# Maintain name index
sadd name:lee 1
sadd name:david 2
sadd name:chris 3

# Get the ID of users having age = 25 and name = lee
sinter age:25 name:lee
  -> will return an empty set

Answer 2

Acually You can do it with put values in key

HMSET lee:25 user_name lee age 25
HMSET massi:43 user_name massi age 43
HMSET lee:24 user_name lee age 24
HMSET lee:28 user_name lee age 28 city Berlin

Now you can find them with "keys" command

127.0.0.1:6379> keys *:25
1) "lee:25"
127.0.0.1:6379> keys lee*
1) "lee:25"
2) "lee:24"
3) "lee:28"
127.0.0.1:6379> keys massi:43
1) "massi:43"

Finally find specific hashes

127.0.0.1:6379> HGETALL lee:24
1) "user_name"
2) "lee"
3) "age"
4) "24"

All that I said is that you can do it in two steps put any number of values that you need in key then find them. But consider that it's not a good idea to put all values inside key Just put ones that you need to do filtering with. Cheers :)