Subject: bug#26807: [PATCH] graph: Add Cypher backend.

From: Roel Janssen <[email-masked]>
Date: Sat, 06 May 2017 23:21:32 +0200

>From 0e9c95ef3473fa7066ccd5991b1c14400aaa7076 Mon Sep 17 00:00:00 2001
From: Roel Janssen <[email-masked]>
Date: Sat, 6 May 2017 23:15:03 +0200
Subject: [PATCH] graph: Add Cypher backend.

* guix/graph.scm (%cypher-backend): New variable.
---
 guix/graph.scm | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/guix/graph.scm b/guix/graph.scm
index 7af2cd3b8..d7fd5f3e4 100644
--- a/guix/graph.scm
+++ b/guix/graph.scm
@@ -229,6 +229,35 @@ nodeArray.push(nodes[\"~a\"]);~%"
                  emit-d3js-prologue emit-d3js-epilogue
                  emit-d3js-node emit-d3js-edge))
 
+
+
+;;;
+;;; Cypher export.
+;;;
+
+(define (emit-cypher-prologue name port)
+  (format port ""))
+
+(define (emit-cypher-epilogue port)
+  (format port ""))
+
+(define (emit-cypher-node id label port)
+  (format port "MERGE (p:Package { id: ~s }) SET p.name = ~s;~%"
+          id label ))
+
+(define (emit-cypher-edge id1 id2 port)
+  (format port "MERGE (a:Package { id: ~s });~%" id1)
+  (format port "MERGE (b:Package { id: ~s });~%" id2)
+  (format port "MATCH (a:Package { id: ~s }), (b:Package { id: ~s }) CREATE UNIQUE (a)-[:NEEDS]->(b);~%"
+          id1 id2))
+
+(define %cypher-backend
+  (graph-backend "cypher"
+                 "Generate Cypher queries."
+                 emit-cypher-prologue emit-cypher-epilogue
+                 emit-cypher-node emit-cypher-edge))
+
+
 
 ;;;
 ;;; Shared.
@@ -236,7 +265,8 @@ nodeArray.push(nodes[\"~a\"]);~%"
 
 (define %graph-backends
   (list %graphviz-backend
-        %d3js-backend))
+        %d3js-backend
+        %cypher-backend))
 
 (define* (export-graph sinks port
                        #:key
-- 
2.12.2

Dear Guix,

I would like to add another backend to the 'guix graph' command.  This
backend will return a bunch of queries that can be used to create a
graph database for any database engine that uses openCypher (although I
only know one engine and it's called neo4j, which should be GPLv3 code).

If there was a way to ensure node definitions are written to the output
before the edges, I could simplify the queries a bit.  But I believe it
is quite fast anyway.

Thanks!

Kind regards,
Roel Janssen