From: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
Date: Sat, 20 Dec 2014 23:00:35 +0000 (-0500)
Subject: neo4j/graph: Add Neo4j as a storage mechanism.
X-Git-Tag: v0.7.1~38^2~5
X-Git-Url: http://nitlanguage.org

neo4j/graph: Add Neo4j as a storage mechanism.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
---

diff --git a/lib/neo4j/graph/graph.nit b/lib/neo4j/graph/graph.nit
index db43a1f..39063f2 100644
--- a/lib/neo4j/graph/graph.nit
+++ b/lib/neo4j/graph/graph.nit
@@ -179,3 +179,100 @@ abstract class GraphStore
 	fun save_part(nodes: Collection[NeoNode],
 			edges: Collection[NeoEdge]) is abstract
 end
+
+# Save or load a graph using an actual Neo4j database.
+class Neo4jGraphStore
+	super GraphStore
+
+	# The maximum number of entities saved in one request.
+	#
+	# Also defines the granulity of the reported progression.
+	#
+	# TODO Also honor this limit in `load`.
+	var batch_max_size = 512 is writable
+
+	# The Neo4j client to use.
+	var client: Neo4jClient
+
+	# The label to use to retrieve the nodes.
+	var node_label: String
+
+	private var done_part = 0
+	private var total = 0
+
+	# Is the database already contains at least one node with the specified label?
+	fun has_node_label(name: String): Bool do
+		var query = new CypherQuery.from_string(
+				"match n where \{name\} in labels(n) return count(n)")
+		query.params["name"] = name
+		var data = client.cypher(query).as(JsonObject)["data"]
+		var result = data.as(JsonArray).first.as(JsonArray).first.as(Int)
+		return result > 0
+	end
+
+	redef fun isolated_save do return not has_node_label(node_label)
+
+	redef fun load do
+		assert batch_max_size > 0
+		fire_started
+		var db_nodes = client.nodes_with_label(node_label)
+		var nodes = graph.nodes
+		var edges = graph.edges
+		var i = 0
+
+		total = nodes.length * 2
+		done_part = nodes.length
+		fire_progressed(done_part, total)
+		for node in db_nodes do
+			nodes.add(node)
+			edges.add_all(node.out_edges)
+			i += 1
+			if i >= batch_max_size then
+				done_part += batch_max_size
+				fire_progressed(done_part, total)
+			end
+		end
+		fire_done
+	end
+
+	redef fun save_part(nodes, edges) do
+		assert batch_max_size > 0
+		fire_started
+		total = nodes.length + edges.length
+		done_part = 0
+
+		save_entities(nodes)
+		save_entities(edges)
+		fire_done
+	end
+
+	# Save the specified entities.
+	private fun save_entities(neo_entities: Collection[NeoEntity]) do
+		var batch = new NeoBatch(client)
+		var batch_length = 0
+
+		for nentity in neo_entities do
+			batch.save_entity(nentity)
+			batch_length += 1
+			if batch_length >= batch_max_size then
+				do_batch(batch)
+				done_part += batch_max_size
+				fire_progressed(done_part, total)
+				batch = new NeoBatch(client)
+				batch_length = 0
+			end
+		end
+		do_batch(batch)
+		done_part += batch_length
+	end
+
+	# Execute `batch` and check for errors.
+	#
+	# Abort if `batch.execute` returns errors.
+	private fun do_batch(batch: NeoBatch) do
+		var errors = batch.execute
+		assert errors.is_empty else
+			for e in errors do sys.stderr.write("{e}\n")
+		end
+	end
+end