added 'useJavascriptSorting' option to simplesort to allow or fallbac…

…k to js sorting

with no indexing on sort property, basic javascript sorting will be faster than loki sorting but may yield  unpredictable results if sort property contains dirty or mixed data.

when indexing is available on sort property, passing 'useJavascriptSorting' option will fallback to javascript sorting if your filtered results amount to 10% or more of total document count.  (best performance tradeoff for most data situations)

See #645 for more info.

benchmark/benchmark_sorting.js

@@ -108,7 +108,7 @@ function sortfun(obj1, obj2) {
   if (obj1.b < obj2.b) return -1;
 }
 
-// unindexed, unfiltered, basic sort function (unsafe for mixed types)
+// unindexed, unfiltered, minimal sort function (pre-jitted)
 function profile1a() {
   var start, end;
   var totalTimes = [];
@@ -198,8 +198,8 @@ function profile3() {
   console.log("'a' filtered, 'b' unindexed : " + totalMS + "ms (" + rate + " ops/s) " + loopIterations + " iterations");
 }
 
-// filtered, unindexed (minimal sort function)
-function profile3b() {
+// filtered, unindexed, minimal sort function (pre-jitted)
+function profile3a() {
   var start, end;
   var totalTimes = [];
   var totalMS = 0;
@@ -229,6 +229,38 @@ function profile3b() {
   console.log("'a' filtered, 'b' unindexed (minimal sort function) : " + totalMS + "ms (" + rate + " ops/s) " + loopIterations + " iterations");
 }
 
+// filtered, unindexed useJavascriptSorting (runtime jit)
+function profile3b() {
+  var start, end;
+  var totalTimes = [];
+  var totalMS = 0;
+  var loopIterations = P2_ITER;
+  var idx, compare, results;
+
+  createDatabase(false);
+
+  for(idx=0; idx<loopIterations; idx++) {
+    compare = Math.floor(Math.random() * QUERY_INDEX_RANGE);
+
+    start = process.hrtime();
+
+    // if we had enabled an index but wanted to force js sorting we would also pass 'disableIndexItercept:true'
+    results = coll.chain().find({a:compare}).simplesort('b', { useJavascriptSorting: true }).data();
+
+    end = process.hrtime(start);
+    totalTimes.push(end);
+  }
+
+  for (var idx = 0; idx < totalTimes.length; idx++) {
+    totalMS += totalTimes[idx][0] * 1e3 + totalTimes[idx][1] / 1e6;
+  }
+
+  totalMS = totalMS.toFixed(2);
+  var rate = loopIterations * 1000 / totalMS;
+  rate = rate.toFixed(2);
+  console.log("'a' filtered, 'b' unindexed (useJavascriptSorting) : " + totalMS + "ms (" + rate + " ops/s) " + loopIterations + " iterations");
+}
+
 function profile4() {
   var start, end;
   var totalTimes = [];
@@ -289,8 +321,9 @@ function profile5() {
   console.log("'a' filtered, 'b' indexed (x-sect): " + totalMS + "ms (" + rate + " ops/s) " + loopIterations + " iterations");
 }
 
-// using 'smart?' simplesort3 which attempts to determine whether
+// using 'smart?' simplesort which attempts to determine whether
 // array intersect or array sort would be more efficient.
+// by default the fallback is to loki sorting (same order as indexes)
 function profile6() {
   var start, end;
   var totalTimes = [];
@@ -318,7 +351,38 @@ function profile6() {
   totalMS = totalMS.toFixed(2);
   var rate = loopIterations * 1000 / totalMS;
   rate = rate.toFixed(2);
-  console.log("'a' filtered, 'b' indexed (smart?): " + totalMS + "ms (" + rate + " ops/s) " + loopIterations + " iterations");
+  console.log("'a' filtered, 'b' indexed (smart): " + totalMS + "ms (" + rate + " ops/s) " + loopIterations + " iterations");
+}
+
+// using 'smart' simplesort with fallback to 'useJavascriptSorting' if filtering
+function profile7() {
+  var start, end;
+  var totalTimes = [];
+  var totalMS = 0;
+  var loopIterations = P4_ITER;
+  var idx, compare, results;
+
+  createDatabase(true);
+
+  for(idx=0; idx < loopIterations; idx++) {
+    compare = Math.floor(Math.random() * QUERY_INDEX_RANGE);
+
+    start = process.hrtime();
+
+    results = coll.chain().find({a:compare}).simplesort("b", { useJavascriptSorting: true }).data();
+
+    end = process.hrtime(start);
+    totalTimes.push(end);
+  }
+
+  for (var idx = 0; idx < totalTimes.length; idx++) {
+    totalMS += totalTimes[idx][0] * 1e3 + totalTimes[idx][1] / 1e6;
+  }
+
+  totalMS = totalMS.toFixed(2);
+  var rate = loopIterations * 1000 / totalMS;
+  rate = rate.toFixed(2);
+  console.log("'a' filtered, 'b' indexed (smart w/js fallback): " + totalMS + "ms (" + rate + " ops/s) " + loopIterations + " iterations");
 }
 
 console.log("loki sorting benchmark diagnostic");
@@ -337,7 +401,9 @@ profile1();
 profile1a();
 profile2();
 profile3();
+profile3a();
 profile3b();
 profile4();
 profile5();
-profile6();
+profile6();
+profile7();