Redis Hashes and sharding

[Shushant Arora]

Redis supports a datatype hash - which is same as hashmap in java.

for redis operation :

In below example does student1 and student2 gets stored on same node as both belong to same hash Student - irrespective of number of nodes in my resis cluster.

HSET Student student1 "ABC" 

HSET Student student2 "DEF"

And also for Redis Spring integration as per http://www.baeldung.com/spring-data-redis-tutorial , The opsForHash() function returns the operations performed on hash values bound to the given key.

Here KEY is fixed string. private static final String KEY = "Student";

hashOps.put(KEY, student.getId(), student);

Will all the data here will go to one node since KEY for all data is same as Student.And it here it is a single key student of type hashmap ?

[Dvir Volk]

Yes, sharding is done by the key, not by the Hash's sub-element. So all HSET operations on the same hash will go to the same shard, always, 

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[Shushant Arora]

Thanks!

And also is it possible to have value of Hash as ListType instead of simple String ?

say HSET Student Subjects "Subject1,Subject2,Subject3"  ?

Thanks

[Jan-Erik Rediger]

No, Redis does not natively support nesting of data structures.
You can built this yourself by either embedding a parseable format
("split the value at ',' to get a list") or by using an indirection
(store an ID/other key name, get the value from the set, then use this
value as a key to get the actual object)

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