In the forum came an interesting proposal for Hibernate OGM.
https://forum.hibernate.org/viewtopic.php?f=31&t=1037739&sid=9ee9d4772ac6dfaa67a37ec02b2c330c&p=2482498#p2482498
Today I think OGM works quite well for document store and even Neo4J because
they don’t have any schema and thus we can store the data in a natural fashion.
For k/v stores, it is so flexible that OGM imposes its tuple structure to
represent the object. This is good enough but has a few drawbacks:
- to read the data back you need the OGM classes around or at least how they
are structured
- being detyped, they tend to be hard to query by the k/v query capability
- we store more data than we could as we copy the column names in each entry
Some k/v stores do have the notion of “schema”. Infinispan uses Protobuf and
ask the user t provide the proto schema. Coherence and Hazelcast uses the
Portable Object Format (invented by the coherence guys AFAIK). Hibernate OGM
makes no use of these. We could use these schema to express the Tuple (which is
essentially a Map) but that’s not what people are looking for I think.
What people are looking for is a way to defined a set of schemas (protobuf or
POF) corresponding to the entities and have OGM use the schema to store a given
serialized entity. This solves the problems above, in particular the capability
to use the native query options of the k/v store and the compactness.
I can see that being conceptually possible as long as we ignore associations.
The schema would describe the properties, even the embeddable and collection of
embeddable objects. As long as these “schema” library let us write the data in
a untyped fashion, something akin to:
entityStructure = schemaLib.as(schemaId);
entityStructure.putProperty(“firstname”, tuple.get(“firstname”) );
addressStructure = entityStructure.addNestedObject(“address”);
addressStructure.addProperty(“city”, tuple.get(“address.city”) );
Note that the user here (see question c), also asks for the ability to
denormalize the data and store a full object graph as one key and only a subset
as a second key which is something we want to do but that we don’t have right
now.
Thoughts?
Emmanuel
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