Merge pull request #300 from bit-cmdr/feature/count-documents-and-est…

…imated-count

docs/collection/count.md

@@ -1,8 +1,8 @@
 # `collection.count`
 
-[Mongo documentation <i class="fa fa-external-link" style="position: relative; top: 2px;" />](http://mongodb.github.io/node-mongodb-native/3.2/api/Collection.html#count)
+[Mongo documentation <i class="fa fa-external-link" style="position: relative; top: 2px;" />](http://mongodb.github.io/node-mongodb-native/3.2/api/Collection.html#countDocuments)
 
-Returns the count of documents that would match a `find()` query. The `collection.count()` method does not perform the `find()` operation but instead counts and returns the number of results that match a query.
+Returns the count of documents that would match a `find()` query. The `collection.count()` method does not perform the `find()` operation but instead counts and returns the number of results that match a query. The method points to `collection.countDocuments()` in the mongo driver.
 
 #### Arguments
 
@@ -21,4 +21,17 @@ A promise
 ```js
 users.count({name: 'foo'})
 users.count('id') // a bit useless but consistent with the rest of the API
+users.count() 
+```
+
+## Getting an estimated count
+
+[Mongo documentation <i class="fa fa-external-link" style="position: relative; top: 2px;" />](http://mongodb.github.io/node-mongodb-native/3.2/api/Collection.html#estimatedDocumentCount)
+
+If you need to get a fast order of magnitude of the count of *all* documents in your collection, you can use the `estimate` option. 
+
+> ⚠️ The `query` argument will be ignored.
+
+```js
+users.count({}, { estimate: true })
 ```

lib/collection.js

@@ -58,8 +58,17 @@ Collection.prototype.count = function (query, opts, fn) {
     opts = {}
   }
 
+  if (typeof query === 'function') {
+    fn = query
+    query = {}
+  }
+
   return this._dispatch(function count (args) {
-    return args.col.count(args.query, args.options)
+    const {estimate, ...options} = args.options
+    if (estimate) {
+      return args.col.estimatedDocumentCount(options)
+    }
+    return args.col.countDocuments(args.query, options)
   })({options: opts, query: query, callback: fn}, 'count')
 }
 

test/collection.js

@@ -415,6 +415,29 @@ test('count > should not ignore options', (t) => {
   })
 })
 
+test('count > should count with no arguments', (t) => {
+  return users.count({ c: 'counting' }).then((count) => {
+    t.is(count, 0)
+    return users.insert({ c: 'counting' })
+  }).then(() => {
+    return users.count()
+  }).then((count) => {
+    t.is(count, 77)
+  })
+})
+
+test('count > should estimate count', (t) => {
+  return users.count({}, { estimate: true }).then((count) => {
+    t.is(count, 51)
+  })
+})
+
+test('count > should estimate count with options', (t) => {
+  return users.count({}, { estimate: true, maxTimeMS: 10000 }).then((count) => {
+    t.is(count, 51)
+  })
+})
+
 test.cb('count > callback', (t) => {
   users.count({ a: 'counting' }, t.end)
 })