From 312a344b8d01e0c54d5eab69205bbf5baef5eb1f Mon Sep 17 00:00:00 2001
From: Chris Watts <devgrok@users.noreply.github.com>
Date: Fri, 4 Dec 2015 01:44:37 +1100
Subject: [PATCH 1/2] Skips loading of the dependency cache if nothing has
 changed. Excludes the cache from equality check as it shouldn't have changed.

---
 packages/constraint-solver/constraint-solver-input.js |  5 ++++-
 packages/constraint-solver/constraint-solver.js       | 11 ++++++-----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/packages/constraint-solver/constraint-solver-input.js b/packages/constraint-solver/constraint-solver-input.js
index 7d8cd7e91d..6e855f71b1 100644
--- a/packages/constraint-solver/constraint-solver-input.js
+++ b/packages/constraint-solver/constraint-solver-input.js
@@ -148,7 +148,10 @@ CS.Input.prototype.isEqual = function (otherInput) {
   // This equality test is also overly sensitive to order,
   // missing opportunities to declare two inputs equal when only
   // the order has changed.
-  return _.isEqual(a.toJSONable(), b.toJSONable());
+  return _.isEqual(
+      _.omit(a.toJSONable(), "catalogCache"),
+      _.omit(b.toJSONable(), "catalogCache")
+  );
 };
 
 CS.Input.prototype.toJSONable = function () {
diff --git a/packages/constraint-solver/constraint-solver.js b/packages/constraint-solver/constraint-solver.js
index 17593be080..b03aca8ac8 100644
--- a/packages/constraint-solver/constraint-solver.js
+++ b/packages/constraint-solver/constraint-solver.js
@@ -56,11 +56,6 @@ CS.PackagesResolver.prototype.resolve = function (dependencies, constraints,
                                 'upgradeIndirectDepPatchVersions'));
   });
 
-  Profile.time(
-    "Input#loadFromCatalog (sqlite)",
-    function () {
-      input.loadFromCatalog(self.catalogLoader);
-    });
 
   var resultCache = self._options.resultCache;
   if (resultCache && resultCache.lastInput &&
@@ -68,6 +63,12 @@ CS.PackagesResolver.prototype.resolve = function (dependencies, constraints,
     return resultCache.lastOutput;
   }
 
+  Profile.time(
+      "Input#loadFromCatalog (sqlite)",
+      function () {
+        input.loadFromCatalog(self.catalogLoader);
+      });
+
   if (options.previousSolution && options.missingPreviousVersionIsError) {
     Profile.time("check for previous versions in catalog", function () {
       _.each(options.previousSolution, function (version, pkg) {

From 0376b477a54f8b90f5ee7c35c8043ec238c6b8c6 Mon Sep 17 00:00:00 2001
From: Avital Oliver <avital@thewe.net>
Date: Wed, 16 Dec 2015 21:05:06 -0800
Subject: [PATCH 2/2] Add clarifying comment on improved constraint solver
 method

Explain a recent change to CS.Input.isEqual that eliminated a very
costly set of SQLite queries against the local package catalog cache
on every app rebuild.
---
 .../constraint-solver/constraint-solver-input.js    | 13 +++++++++++--
 packages/constraint-solver/constraint-solver.js     |  8 ++++----
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/packages/constraint-solver/constraint-solver-input.js b/packages/constraint-solver/constraint-solver-input.js
index 6e855f71b1..e4fd5bf392 100644
--- a/packages/constraint-solver/constraint-solver-input.js
+++ b/packages/constraint-solver/constraint-solver-input.js
@@ -148,9 +148,18 @@ CS.Input.prototype.isEqual = function (otherInput) {
   // This equality test is also overly sensitive to order,
   // missing opportunities to declare two inputs equal when only
   // the order has changed.
+
+  // Omit `catalogCache` -- it's not actually part of the serialized
+  // input object (it's only in `toJSONable()` for tests).
+  //
+  // Moreover, catalogCache is populated as-needed so their values for
+  // `a` and `b` will very likely be different even if they represent
+  // the same input. So by omitting `catalogCache` we no longer need
+  // to reload the entire relevant part of the catalog from SQLite on
+  // every rebuild!
   return _.isEqual(
-      _.omit(a.toJSONable(), "catalogCache"),
-      _.omit(b.toJSONable(), "catalogCache")
+    _.omit(a.toJSONable(), "catalogCache"),
+    _.omit(b.toJSONable(), "catalogCache")
   );
 };
 
diff --git a/packages/constraint-solver/constraint-solver.js b/packages/constraint-solver/constraint-solver.js
index b03aca8ac8..7f89d69556 100644
--- a/packages/constraint-solver/constraint-solver.js
+++ b/packages/constraint-solver/constraint-solver.js
@@ -64,10 +64,10 @@ CS.PackagesResolver.prototype.resolve = function (dependencies, constraints,
   }
 
   Profile.time(
-      "Input#loadFromCatalog (sqlite)",
-      function () {
-        input.loadFromCatalog(self.catalogLoader);
-      });
+    "Input#loadFromCatalog (sqlite)",
+    function () {
+      input.loadFromCatalog(self.catalogLoader);
+    });
 
   if (options.previousSolution && options.missingPreviousVersionIsError) {
     Profile.time("check for previous versions in catalog", function () {