neo4j - how to snapshot everything in a label

Question

Im using neo4j to store information about maps and sensors. Every time the map or sensor layout changes I need to keep a copy. I can imagine querying and manually creating said copy but I'm wondering if it's possible to build a neo4j type query that would do this for me.

So far all I've come up with is a way to replicate the nodes in a given label:

match ( a:some_label { some_params }) with a create ( b:some_label ) set b=a,b.other_id=value;

This would allow me to put version and time stamp info on a given snap shot.

What it doesn't do is copy the edge information. Suggestions? Maybe a second (similar) query?

cybersam cybersam · Accepted Answer · 2014-09-30T23:31:51

If I understand you correctly, you are essentially trying to maintain a history of the state of a node and the state of its incoming relationship. One way to do this is to chain the nodes in reverse chronological order.

For example, suppose the nodes in the chain are labeled Some_label and the relationships are of type SOME_TYPE. The head node of the chain is always the current (most recent) node. Unless a Some_label node is chronologically the earliest node in the chain, it will have a SOME_TYPE relationship to the previous version of the node.

Here is how you'd insert a new relationship and node (with some properties) at the head of the chain. (Just to set up this example, I assume that the first node in the chain is linked to by some node labeled HeadRef).

MATCH (x:HeadRef)-[r1:SOME_TYPE]->(a1:Some_label)
CREATE (x)-[r2:SOME_TYPE {x: "ghi"}]->(a2:Some_label {a:123, b: true})-[r:SOME_TYPE]->(a1)
SET r=r1
WITH r1
DELETE r1

Note that this approach is also much more performant than maintaining your own other_id property to link nodes together. You should always use relationships instead -- that is the graph DB way.

neo4j - how to snapshot everything in a label

1 Answers