Support custom syntax for Neo4j OGM

[fbiville]

Neo4j OGM and Spring Data Neo4j lets developers think in terms of their business domain rather than nodes and relationships.

The idea would be to provide a custom XML schema that allows to express migrations in terms of entities, rather than raw Cypher queries.

For instance, we could imagine something like:

<changelog [...]>
   <changeset [...]>
      <insert entity="com.foo.Movie">
          <property name="title">Matrix</property>
      </insert>
      <remove entity="com.foo.Actor">
          <where>
             <property name="firstName">Ronald</property>
          </where>
      </insert>
   </changeset>
</changelog>

This is just a rough idea of what it could be like.
In the long term, we need to think about:

• creating relationship entities as well (maybe have a <insertNode> and <insertRelationship><from /><to />
• supporting comparisons other than strict equality (>, >=, <, <=, ...)?
• making it work alongside usual XML changesets (we should be able to mix both)

[fbiville]

And that custom schema... should much probably be GraphML!
I received an email the other day complaining about something related:

Hi,
The support package [of nosqlunit-neo4j] is removed from Spring Data Neo4j 4 so IndexingNodeTypeRepresentationStrategy is not present there due to which following graph is not being converted to POJO.

<?xml version="1.0" encoding="UTF-8"?>
<graphml xmlns="http://graphml.graphdrawing.org/xmlns"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns
 http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
	<graph id="G" edgedefault="directed">
		<key id="__type__" for="node" attr.name="__type__" attr.type="string"></key>
		<key id="productId" for="node" attr.name="productId" attr.type="string"></key>

		<node id="3">
			<data key="__type__">com.etilize.burraq.datasource.Product</data>
			<data key="productId">100001235</data>
			<index name="__types__" key="className">com.etilize.burraq.datasource.Product
			</index>
		</node>
	</graph>
</graphml>

Can you please let me know any alternative as it's a blocker in using nosqlunit-neo4j with Spring data neo4j 4. Thank you.

Even though the email is about nosqlunit-neo4j, the XML above is a good example of something Liquigraph for Neo4j OGM should support.

[fbiville]

After a discussion some time ago, let's stick to the basic schema we have.