MGET sort of thing for Redis Hashes

[arun-j02]

Discussed in #2489

^{Originally posted by arun-j98 August 19, 2023}
Hey, just wanted to ask like we have mget to get multiples keys-value pairs at once. Do we have something similar for getting redis hashes? UseCase: we have stored a multi level map {k1 : {f1: v1, f2, v2}, k2 : {f1: v1, f2: v2}} as redis hash. I want to pass k1, k2 as the list of keys and want to get the full data for k1, k2 ==> {k1 : {f1: v1, f2, v2}, k2 : {f1: v1, f2: v2}}. I know redis-cli doesn't support mget sort of thing for hashes, but like does lettuce on its side might do some pipelining or something.
Currently, we are doing this...we have a list of keys [k1, k2 ... kn] and for each key we are making a redis call. if the list is large then latencies are increasing which is obvious.

[arun-j02]

@mp911de Please can you help

[stevekradel-okta]

This probably doesn't belong as any sort of Lettuce feature as it sounds like you are using a custom data structure. Lettuce already pipelines everything it can; consider if a lua script might provide a further boost.

[arun-j02]

We have a Key : Fields : Data
We can use hget to get a particular key: field combination. hmget to get key : fields combination say k:f1, k:f2, k:f3 and hgetall to get all. Now given a list of keys, can get data for those keys all in one go? One go as in lettuce can make a connection and then get the data for these keys. Just like it is doing for mget(keys) without giving Cross slot error.

[mp911de]

HMGET operates on a single hash key. If you want to fetch HMGET from many hashes, then you need to issue these commands yourself.