From a08dd7ecce839401d40d6b866b30bc0c0ce0976a Mon Sep 17 00:00:00 2001
From: Ansis Brammanis <ansis.brammanis@gmail.com>
Date: Fri, 11 Jan 2013 19:14:17 -0500
Subject: [PATCH 1/2] More efficient parentways

---
 js/id/graph/graph.js | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/js/id/graph/graph.js b/js/id/graph/graph.js
index 868c17de5..4729bd101 100644
--- a/js/id/graph/graph.js
+++ b/js/id/graph/graph.js
@@ -36,19 +36,27 @@ iD.Graph.prototype = {
     },
 
     parentWays: function(entity) {
-        var graph = this;
-        return this.transient(entity, 'parentWays',
-            function generateParentWays() {
-            var o = [];
+        var graph = this,
+            ent,
+            node;
+
+        if (!graph.calculatedParentWays) {
             for (var i in graph.entities) {
-                if (graph.entities[i] &&
-                    graph.entities[i].type === 'way' &&
-                    graph.entities[i].nodes.indexOf(this.id) !== -1) {
-                    o.push(graph.entities[i]);
+                ent = graph.entities[i];
+                if (ent && ent.type === 'way') {
+                    for (var j = 0; j < ent.nodes.length; j++) {
+                        node = graph.entities[ent.nodes[j]];
+                        node.parentways = node.parentways || [];
+                        if (node.parentways.indexOf(ent) < 0) {
+                            node.parentways.push(ent);
+                        }
+                    }
                 }
             }
-            return o;
-        });
+            graph.calculatedParentWays = true;
+        }
+
+        return entity.parentways || [];
     },
 
     parentRelations: function(entity) {

From 62e78b5b9b9adaeea033e1fa737144e8f08893e1 Mon Sep 17 00:00:00 2001
From: Ansis Brammanis <ansis.brammanis@gmail.com>
Date: Fri, 11 Jan 2013 20:37:32 -0500
Subject: [PATCH 2/2] clean up parentWays

---
 js/id/graph/graph.js | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/js/id/graph/graph.js b/js/id/graph/graph.js
index 4729bd101..b6d0485b3 100644
--- a/js/id/graph/graph.js
+++ b/js/id/graph/graph.js
@@ -11,6 +11,7 @@ iD.Graph = function(entities) {
     }
 
     this.transients = {};
+    this._parentWays = {};
 
     if (iD.debug) {
         Object.freeze(this);
@@ -37,18 +38,18 @@ iD.Graph.prototype = {
 
     parentWays: function(entity) {
         var graph = this,
-            ent,
-            node;
+            entity,
+            id;
 
         if (!graph.calculatedParentWays) {
             for (var i in graph.entities) {
-                ent = graph.entities[i];
-                if (ent && ent.type === 'way') {
-                    for (var j = 0; j < ent.nodes.length; j++) {
-                        node = graph.entities[ent.nodes[j]];
-                        node.parentways = node.parentways || [];
-                        if (node.parentways.indexOf(ent) < 0) {
-                            node.parentways.push(ent);
+                entity = graph.entities[i];
+                if (entity && entity.type === 'way') {
+                    for (var j = 0; j < entity.nodes.length; j++) {
+                        id = entity.nodes[j];
+                        this._parentWays[id] = this._parentWays[id] || [];
+                        if (this._parentWays[id].indexOf(entity) < 0) {
+                            this._parentWays[id].push(entity);
                         }
                     }
                 }
@@ -56,7 +57,7 @@ iD.Graph.prototype = {
             graph.calculatedParentWays = true;
         }
 
-        return entity.parentways || [];
+        return this._parentWays[entity.id] || [];
     },
 
     parentRelations: function(entity) {