MongoDB: Adding placeholders for group by support. Currently not implemented.

mongo/collection.go

@@ -45,6 +45,7 @@ type chunks struct {
 	Offset     int
 	Sort       []string
 	Conditions interface{}
+	GroupBy    []interface{}
 }
 
 func (self *Collection) Find(terms ...interface{}) db.Result {

mongo/database_test.go

@@ -24,6 +24,7 @@
 package mongo
 
 import (
+	"math/rand"
 	"os"
 	"reflect"
 	"strings"
@@ -267,6 +268,68 @@ func TestResultCount(t *testing.T) {
 
 }
 
+func TestGroup(t *testing.T) {
+
+	var err error
+	var sess db.Database
+	var stats db.Collection
+
+	if sess, err = db.Open(Adapter, settings); err != nil {
+		t.Fatal(err)
+	}
+
+	type stats_t struct {
+		Numeric int `db:"numeric" bson:"numeric"`
+		Value   int `db:"value" bson:"value"`
+	}
+
+	defer sess.Close()
+
+	if stats, err = sess.Collection("stats_test"); err != nil {
+		if err != db.ErrCollectionDoesNotExist {
+			t.Fatal(err)
+		}
+	}
+
+	// Truncating table.
+	if err == nil {
+		if err = stats.Truncate(); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// Adding row append.
+	for i := 0; i < 1000; i++ {
+		numeric, value := rand.Intn(10), rand.Intn(100)
+		if _, err = stats.Append(stats_t{numeric, value}); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// db.stats_test.group({key: {numeric: true}, initial: {sum: 0}, reduce: function(doc, prev) { prev.sum += 1}});
+
+	// Testing GROUP BY
+	res := stats.Find().Group(bson.M{
+		"key":     bson.M{"numeric": true},
+		"initial": bson.M{"sum": 0},
+		"reduce":  `function(doc, prev) { prev.sum += 1}`,
+	})
+
+	var results []map[string]interface{}
+
+	err = res.All(&results)
+
+	// Currently not supported.
+	if err != db.ErrUnsupported {
+		t.Fatal(err)
+	}
+
+	//if len(results) != 10 {
+	//	t.Fatalf(`Expecting exactly 10 results, this could fail, but it's very unlikely to happen.`)
+	//}
+
+}
+
 // This test uses and result and tries to fetch items one by one.
 func TestResultFetch(t *testing.T) {
 

mongo/result.go

@@ -116,6 +116,13 @@ func (self *Result) All(dst interface{}) error {
 	return nil
 }
 
+// Used to group results that have the same value in the same column or
+// columns.
+func (self *Result) Group(fields ...interface{}) db.Result {
+	self.queryChunks.GroupBy = fields
+	return self
+}
+
 // Fetches only one result from the resultset.
 func (self *Result) One(dst interface{}) error {
 	var err error
@@ -187,6 +194,10 @@ func (self *Result) query() (*mgo.Query, error) {
 
 	q := self.c.collection.Find(self.queryChunks.Conditions)
 
+	if self.queryChunks.GroupBy != nil {
+		return nil, db.ErrUnsupported
+	}
+
 	if self.queryChunks.Offset > 0 {
 		q = q.Skip(self.queryChunks.Offset)
 	}