How do i check hash data exists by hashname?
> hset test record1 data1
> hset test record2 data2
> hset test record3 data3
> hgetall test
127.0.0.1:6379> hgetall test
1) "record1"
2) "data1"
3) "record2"
4) "data2"
5) "record3"
6) "data3"
127.0.0.1:6379> hexists test
(error) ERR wrong number of arguments for 'hexists' command
Thanks In Advance
Try this command, it will solve your problem.
redis> EXISTS test
(integer) 1
You could use HLEN, if that returns zero then they hash does not exist.
redis> HLEN test
(integer) 3
redis> HLEN non_existent_hash_key
(integer) 0
Related
I am storing some values in redis like for key: 1 the value will be
{"counter":1,"counter1":2}
Now I need to reset value of counter while the counter1 should be remaining same.
To increase counter I am use the command SETEX mykey 60 redis .
But it will also reset the value of counter1. So is there any way I can reset one value for a single key.
Let me know if I need to add some more info.
Instead of string you may use hash, then it will be easy. you can increment by some other value, delete counter etc etc. Each key in your json will be hash field.
127.0.0.1:6379> hset mykey counter 1 counter1 2
(integer) 2
127.0.0.1:6379> hgetall mykey
1) "counter"
2) "1"
3) "counter1"
4) "2"
127.0.0.1:6379> hset mykey counter 25
(integer) 0
127.0.0.1:6379> hgetall mykey
1) "counter"
2) "25"
3) "counter1"
4) "2"
127.0.0.1:6379> HINCRBY mykey counter 15
(integer) 40
127.0.0.1:6379> hgetall mykey
1) "counter"
2) "40"
3) "counter1"
4) "2"
127.0.0.1:6379>
Assuming that myhash is like:
redis 127.0.0.1:6379> HSET myhash field1 "foo"
(integer) 1
redis 127.0.0.1:6379> HSET myhash field2 "bar"
(integer) 1
redis 127.0.0.1:6379> HGETALL myhash
1) "field1"
2) "Hello"
3) "field2"
4) "World"
How can I get number of myhash elements, that is 2, from redis-cli?
I'm learning redis from this tutorial but could not find my answer there.
You can use the HLEN command. Taken directly from the documentation at redis.io:
redis> HSET myhash field1 "Hello"
(integer) 1
redis> HSET myhash field2 "World"
(integer) 1
redis> HLEN myhash
(integer) 2
redis>
In a redis-cli session:
127.0.0.1:6379> SET somekey "Greetings"
OK
127.0.0.1:6379> SET somekey "Mortal"
OK
127.0.0.1:6379> EXISTS somekey
(integer) 1
I am looking for a function SOMEFUNC that searches for a key and a value. Perhaps something such as:
127.0.0.1:6379> SOMEFUNC "somekey:Greetings"
(integer) 1
127.0.0.1:6379> SOMEFUNC "somekey:Ave"
(integer) 0
It's all driven by a program, so I could use SSCAN on the key and compare, but I'm wondering if there is SOMEFUNC that will do this directly, as the statements above illustrate.
As noted by #MrWiggles, there is no such SOMEFUNC for Strings. On top of the two alternatives that he suggests, another that could get you pretty close is using Hashes instead. Consider the following:
127.0.0.1:6379> HSET somehash "Greetings" ""
(integer) 1
127.0.0.1:6379> HEXISTS somehash "Greetings"
(integer) 1
127.0.0.1:6379> HEXISTS somehash "Mortal"
(integer) 0
127.0.0.1:6379> HEXISTS someotherhash "Ave"
(integer) 0
Sets can also do the same trick:
127.0.0.1:6379> SADD someset "Greetings"
(integer) 1
127.0.0.1:6379> SISMEMBER someset "Greetings"
(integer) 1
127.0.0.1:6379> SISMEMBER someset "Mortal"
(integer) 0
127.0.0.1:6379> SISMEMBER someotherset "Ave"
(integer) 0
That said, note that Hashes & Sets have memory overheads (just like Strings). For 100,000 String/Hash/Set keys, here's what my local Redis' INFO MEMRORY reports for used_memory(_human):
Strings: 9594616 (9.15M)
Hashes: 11194616 (10.68M)
Sets: 25594616 (24.1M)
The real question, however, is why you want to keep everything in separate keys. Unless there's a compelling reason not to do so in your use case, consider a single Hash as a mini-store for all of your "keys" (fields) and values, e.g.:
127.0.0.1:6379> HSET minikv somekey Greetings
(integer) 1
127.0.0.1:6379> HSET minikv anotherkey Human
(integer) 1
...
In terms of your original question, this will bring you back to square one - meaning you'll have to read (HGET minikv somekey) and compare in your app or, my favorite, wrap it in Lua to do it in one call, perhaps like this:
127.0.0.1:6379> EVAL "return redis.call('HGET', KEYS[1], ARGV[1]) == ARGV[2] and 1 or 0" 1 minikv somekey Greetings
(integer) 1
127.0.0.1:6379> EVAL "return redis.call('HGET', KEYS[1], ARGV[1]) == ARGV[2] and 1 or 0" 1 minikv somekey Mortal
(integer) 0
127.0.0.1:6379> EVAL "return redis.call('HGET', KEYS[1], ARGV[1]) == ARGV[2] and 1 or 0" 1 minikv anotherkey Mortal
(integer) 0
127.0.0.1:6379> EVAL "return redis.call('HGET', KEYS[1], ARGV[1]) == ARGV[2] and 1 or 0" 1 minikv anotherkey Human
(integer) 1
The nice thing about using this minikv Hash is the footprint - a 100K Hash INFO memory:
used_memory:8519088
used_memory_human:8.12M
There is nothing built in to Redis that will do this for you.
A couple of ways of achieving this are:
Fetch the value of the key back into your application and then check the value to see if it equals what you want it to
Use a Lua script to do this on the redis server
As in the doc http://redis.io/commands/sort
SORT mylist BY weight_*
What I would want to do is something like
SORT mylist BY (weight_* + vote_*)
Is that possible to do this just by Redis?
You can use Lua to build each sum_* key and sort by those:
redis 127.0.0.1:6379> sadd myset 1 2 3
(integer) 0
redis 127.0.0.1:6379> mset weight_1 1 weight_2 2 weight_3 3
OK
redis 127.0.0.1:6379> mset vote_1 1 vote_2 2 vote_3 0
OK
redis 127.0.0.1:6379> eval "for i in ipairs(redis.call('smembers', KEYS[1])) do redis.call('set', 'sum_' .. i, redis.call('get','weight_' .. i) + redis.call('get', 'vote_' .. i)) end;" 1 myset
(nil)
redis 127.0.0.1:6379> sort myset by sum_*
1) "1"
2) "3"
3) "2"
I can't seem to find useful information about Redis commands. I want to know the data type of the value of a given key. For instance to list all the keys of my database I run the following command:
keys *
In my setup, I get the following result:
1) "username:testuser:uid"
2) "uid:1:first"
3) "uid:1:email"
4) "uid:1:hash"
5) "global:next_uid"
6) "members:email"
7) "uid:1:username"
8) "uid:1:last"
9) "uid:1:salt"
10) "uid:1:access"
11) "uid:1:company"
12) "email:testuser#gmail.com:uid"
13) "uid:1:phone_number"
How do I know what data type the key members:email contains? I tried to run get members:email but and I get the error (error) ERR Operation against a key holding the wrong kind of value
Any thoughts?
You could use the type command:
http://redis.io/commands/type
See below from docs:
redis> SET key1 "value"
"OK"
redis> LPUSH key2 "value"
(integer) 1
redis> SADD key3 "value"
(integer) 1
redis> TYPE key1
"string"
redis> TYPE key2
"list"
redis> TYPE key3
"set"
redis>