Is there MGET analog for Redis hashes?

Question

I'm planning to start using hashes insead of regular keys. But I can't find any information about multi get for hash-keys in Redis wiki. Is this kind of command is supported by Redis?

Thank you.

Answer 1

You can query hashes or any keys in pipeline, i.e. in one request to your redis instance. Actual implementation depends on your client, but with redis-py it'd look like this:

pipe = conn.pipeline() pipe.hgetall('foo') pipe.hgetall('bar') pipe.hgetall('zar') hash1, hash2, hash3 = pipe.execute() 

Client will issue one request with 3 commands. This is the same technique that is used to add multiple values to a set at once.

Read more at http://redis.io/topics/pipelining

Answer 2

If SORT let you use multiple GETs with the -> syntax, and all your hashes had the same fields, you could get them in a bulk reply by putting their names into a set and sorting that.

  SORT names_of_hashes GET *->field1 *->field2 *->field3 *->etc 

But it doesn't look like you can do that with the hash access. Plus you'd have to turn the return list back into hashes yourself.

UPDATE: Redis seems to let you fetch multiple fields if you name your hashes nicely:

redis> hset hash:1 name fish (integer) 1 redis> hset hash:2 name donkey (integer) 1 redis> hset hash:3 name horse (integer) 1 redis> hset hash:1 type fish (integer) 1 redis> hset hash:2 type mammal (integer) 1 redis> hset hash:3 type mammal (integer) 1 redis> sadd animals 1 (integer) 1 redis> sadd animals 2 (integer) 1 redis> sadd animals 3 (integer) 1 redis> sort animals get # get hash:*->name get hash:*->type 1. "1" 2. "fish" 3. "fish" 4. "2" 5. "donkey" 6. "mammal" 7. "3" 8. "horse" 9. "mammal"