Improve performance of document creation.

The most common case for _pathToPositionalSyntax is that there's no
positional syntax present. By avoiding the two calls to Regexp.replace,
we can avoid creating two additional copies of the given path string per
call. During document creation this function is called very frequently.

By avoiding extraneous calls to string split, we can reduce the number
of string copies performed and garbage generated as a result.

benchmarks/create.js

@@ -30,8 +30,9 @@ const doc = JSON.parse(fs.readFileSync(__dirname + '/bigboard.json'));
 // console.error('reading from disk and parsing JSON took %d ms', time1);
 
 const start2 = new Date();
-for (let i = 0; i < 1000; ++i) {
+const iterations = 1000;
+for (let i = 0; i < iterations; ++i) {
   new Board(doc);
 }
 const time2 = (new Date - start2);
-console.error('creation of large object took %d ms', time2);
+console.error('creation of large object took %d ms, %d ms per object', time2, time2 / iterations);

lib/document.js

@@ -306,7 +306,7 @@ function $__applyDefaults(doc, fields, skipId, exclude, hasIncludedChildren, isB
     }
 
     const type = doc.schema.paths[p];
-    const path = p.split('.');
+    const path = p.indexOf('.') === -1 ? [p] : p.split('.');
     const len = path.length;
     let included = false;
     let doc_ = doc._doc;
@@ -982,7 +982,7 @@ Document.prototype.$set = function $set(path, val, type, options) {
   }
 
   let schema;
-  const parts = path.split('.');
+  const parts = path.indexOf('.') === -1 ? [path] : path.split('.');
 
   // Might need to change path for top-level alias
   if (typeof this.schema.aliases[parts[0]] == 'string') {

lib/schema.js

@@ -817,6 +817,9 @@ function _getPath(schema, path, cleanPath) {
  */
 
 function _pathToPositionalSyntax(path) {
+  if (!/\.\d+/.test(path)) {
+    return path;
+  }
   return path.replace(/\.\d+\./g, '.$.').replace(/\.\d+$/, '.$');
 }
 
@@ -1084,7 +1087,7 @@ Schema.prototype.indexedPaths = function indexedPaths() {
 
 Schema.prototype.pathType = function(path) {
   // Convert to '.$' to check subpaths re: gh-6405
-  const cleanPath = path.replace(/\.\d+\./g, '.$.').replace(/\.\d+$/, '.$');
+  const cleanPath = _pathToPositionalSyntax(path);
 
   if (this.paths.hasOwnProperty(path)) {
     return 'real';