[Aerogear-users] Many-To-Many Data Store relationship SQLStore
supittma at redhat.com
Fri Sep 12 10:52:21 EDT 2014
On 9/11/2014 2:20 PM, Ramon Pires da Silva wrote:
> the Data Store with SQLStore for android sample at github are really
> simple, i need some example how to work with many-to-many
> relationship,or some tip about it.
SQLStore really doesn't support many-to-many style relationships*. If
you need a full ORM with proxies, lazy loading, etc then that is a
different problem. If you can get by with Key:Value mappings and some
simple querying then we might be able to help.
For each pair of relationships you can create a mapping object and use
three SQLStores. Two stores would be for your objects and the third
would be a for the object which manages the mapping (essentially a
RecordId and a pair of Ids for the other two objects). Then I would
wrap these three stores in a ContentProvider which will manage
assembling and disassembling your objects when the app queries them.
*SQLStore works by serializing your object to JSON and then storing each
property in a table. The table schema is (from my memory) is the fully
qualified property name, the property value, a row id, and the id of the
parent row. It is really good for storing objects which are basically
unidirectional graphs with a unique key. It is very slow at doing any
other querying, and it can't handle complex graphs (Many to many,
cycles, etc). It can handle nested collections however.
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