How to iterate over Redis keys to get their values? - redis

Question

How do I iterate over objects in Redis and get all their values? Something like this:
scan object* hgetall
This should return
age 22 password 1234 username Sarah
age 20 password 5678 username Mike
When Redis contains this data:
hmset objectSarah age 22 password 1234 username Sarah
hmset objectMike age 20 password 5678 username Mike
Thanks

Answer 1

You can't do that with just one command, you'll need to scan and then process the results (i.e. HGETALL them) one by one.
You could, however, wrap this into a Lua script (see EVAL) that accepts the current cursor and fetches the data before returning everything to the client. I.e.:
local cur, pat = tonumber(ARGV[1]), ARGV[2]
local scan = redis.call('SCAN', cur, 'MATCH', pat)
for i, v in ipairs(scan[2]) do
local data = redis.call('HGETALL', v)
scan[2][i] = { v, data }
end
return scan
Runtime example:
127.0.0.1:6379> hmset objectSarah age 22 password 1234 username Sarah
OK
127.0.0.1:6379> hmset objectMike age 20 password 5678 username Mike
OK
127.0.0.1:6379> script load "..."
"d81ace3345591b4fee7f3bf4cf28e7b260b59554"
127.0.0.1:6379> evalsha d81ace3345591b4fee7f3bf4cf28e7b260b59554 0 0 object*
1) "0"
2) 1) 1) "objectSarah"
2) 1) "age"
2) "22"
3) "password"
4) "1234"
5) "username"
6) "Sarah"
2) 1) "objectMike"
2) 1) "age"
2) "20"
3) "password"
4) "5678"
5) "username"
6) "Mike"
Notes:
This is actually cluster-safe and the use of programmatically-generated key names here should be ok.
Be careful of HGETALL w/ big hashes.
Scanning is not recommended for big datasets and/or for providing fast responses