Re: [hibernate-dev] Proposal for a Redis module in Hibernate OGM
Hi Mark,
Many thanks for giving this a try; Your work looks impressive, it's very
advanced for an initial dialect contribution, covering many advanced cases
already. So kudos for that!
Please find some remarks and questions below.
Cheers,
--Gunnar
2015-07-17 17:16 GMT+02:00 Mark Paluch <mpaluch(a)paluch.biz>:
Hi there,
I created a Redis module for Hibernate OGM, based on OGM 4.2. Redis is a
Key-Value store supporting Lists, Hashes (Maps), Sorted Sets, ...
I took the Infinispan/CouchDB approach storing entities and associations as
JSON documents within Redis Hashes. A Map<Object, Map<Object, Object>>
corresponds with a Redis Hash.
The entity table maps to the Hash Id, the entity Id to the key of the hash
and the set of columns is enclosed within a JSON (currently). Supported
features are:
* Composite Id's
* Embedded associations
* External associations
* I saw you create a hash per entity type, using the ids as keys within
this hash and a JSON document modelling the properties of a given entity
instance.
Have you considered to store JSON documents on the "top-level" instead?
This would require to encode the table name into the key as well (similar
to as we do it for CouchDB): "Order:123" -> ... . The reason I am asking is
that I am wondering whether it may be a source of contention and/or whether
it may pose scaling issues if all entities of one type are stored within a
single hash.
Using JSON for the actual entity contents seems reasonable and a common
approach in the Redis world from what I've read, so +1 for doing this from
me. How would the "more native" approach look like you describe below?
Would we have to serialise everything ourselves into String/byte[]? If so,
I am not sure whether that's of much usefulness actually and I'd be
inclined to go the JSON route exclusively. As you say, it also works nicely
for hierarchical structures.
* The id is used as key and also part of the JSON value. Could it be
removed from the latter?
* Do you have any ideas how Redis-specific structures could be exposed
which do not map exactly to entities, e.g. Lists stored directly via some
key?
* Our option system could be used to expose specific settings such as TTL
for given entities
* Is there any form of transaction support in Redis we could leverage?
and I guess many more, that I'm currently not aware of :-)
There are various ways (JSON, Java-serialized simulating Documents) how to
store data within Redis.
Another approach could be storing Tuples within Redis more native, since
they are in the end Maps, somehow. However, mapping tuples to Redis fit a
native storage but raises questions about Id's, limited data type support
(there is no equivalent for nested lists/maps). So the more native approach
would require distributing data amongst various data types, depending on
the supported features, and would require more IO's.
My impl can be used to interoperate with other clients from the C, Ruby,
Python, Node.js, ... worlds. The JSON is clean and does not look awkward on
the first look.
The current code can be found below
https://github.com/mp911de/hibernate-ogm/tree/redis. Most TCK tests pass,
only some 15 tests fail. Mostly due to enum and JTA support. Couldn't
figure out, how to fix it, so need your help to figure it out.
I'll take a closer look at your change asap. Could you create a pull
request from your branch against the upstream repo? Then we can have a
discussion right there.
Hope, I made you hungry for the Redis OGM module. Let's start a discussion
based on my proposal for inclusion and let's see, where we end
up.
Yep, it looks very promising and I think it'd be great to have support for
Redis in OGM :) We'll need your continued help though to make it happen and
evolve it in the future as Redis itself and OGM core advance.
Best regards, Mark
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