Merge pull request #24 from rugbyhead/master

Ability to pass a query to filter documents before analysis

README.markdown

@@ -86,6 +86,14 @@ The default will traverse all the way to the bottom of that structure:
 
 As you can see, variety only traversed three levels deep.
 
+### Analyze a subset of Documents ###
+
+Perhaps you have a large collection, or you only care about some subset of the documents.
+
+One can apply a "query" contraint, which takes a standard Mongo query object, to filter the set of documents required before analysis.
+
+    $ mongo test --eval "var collection = 'users', query = {'caredAbout':true}" variety.js
+
 ##### "But my dad told me MongoDB is a schemaless database!" #####
 
 First of all, your father is a great guy. Moving on...

variety.js

@@ -51,7 +51,10 @@ if (db[collection].count() == 0) {
         "Possible collection options for database specified: " + collNames + ".";
 }
 
-if (typeof limit === "undefined") { var limit = db[collection].count(); }
+if (typeof query === "undefined") { var query = {}; }
+print("Using query of " + query.toSource());
+
+if (typeof limit === "undefined") { var limit = db[collection].find(query).count(); }
 print("Using limit of " + limit);
 
 if (typeof maxDepth === "undefined") { var maxDepth = 99; }
@@ -182,7 +185,7 @@ var addVarietyResults = function(result) {
 }
 
 // main cursor
-db[collection].find().sort({_id: -1}).limit(limit).forEach(function(obj) {
+db[collection].find(query).sort({_id: -1}).limit(limit).forEach(function(obj) {
   var recordResult = {};
   for (var key in obj) {
     if(obj.hasOwnProperty(key)) {
@@ -229,7 +232,7 @@ resultsDB[resultsCollectionName].find({}).forEach(function(key) {
   if(limit < numDocuments) {
     var existsQuery = {};
     existsQuery[keyName] = {$exists: true};
-    key.totalOccurrences = db[collection].count(existsQuery);
+    key.totalOccurrences = db[collection].find(query).count(existsQuery);
   }  
   key.percentContaining = (key.totalOccurrences / numDocuments) * 100.0;
   resultsDB[resultsCollectionName].save(key);