add 'distinct' option to node query to return list of distinct values…

…. must be for an indexed field in node.attributes

shock-server/controller/node/multi.go

@@ -72,7 +72,7 @@ func (cr *NodeController) ReadMany(ctx context.Context) error {
 
 	// Gather params to make db query. Do not include the following list.
 	if _, ok := query["query"]; ok {
-		paramlist := map[string]int{"query": 1, "limit": 1, "offset": 1, "order": 1, "direction": 1}
+		paramlist := map[string]int{"query": 1, "limit": 1, "offset": 1, "order": 1, "direction": 1, "distinct": 1}
 		for key := range query {
 			if _, found := paramlist[key]; !found {
 				keyStr := fmt.Sprintf("attributes.%s", key)
@@ -86,7 +86,7 @@ func (cr *NodeController) ReadMany(ctx context.Context) error {
 			}
 		}
 	} else if _, ok := query["querynode"]; ok {
-		paramlist := map[string]int{"querynode": 1, "limit": 1, "offset": 1, "order": 1, "direction": 1, "owner": 1, "read": 1, "write": 1, "delete": 1, "public_owner": 1, "public_read": 1, "public_write": 1, "public_delete": 1}
+		paramlist := map[string]int{"querynode": 1, "limit": 1, "offset": 1, "order": 1, "direction": 1, "distinct": 1, "owner": 1, "read": 1, "write": 1, "delete": 1, "public_owner": 1, "public_read": 1, "public_write": 1, "public_delete": 1}
 		for key := range query {
 			if _, found := paramlist[key]; !found {
 				for _, value := range query[key] {
@@ -144,6 +144,23 @@ func (cr *NodeController) ReadMany(ctx context.Context) error {
 	// Combine permissions query with query parameters and ACL query into one AND clause
 	q["$and"] = []bson.M{qPerm, qOpts, qAcls}
 
+	// process distinct query
+	if _, ok := query["distinct"]; ok {
+		dField := query.Get("distinct")
+		if !node.HasAttributeField(dField) {
+			err_msg := "err unable to run distinct query on non-indexed attributes field: " + dField
+			logger.Error(err_msg)
+			return responder.RespondWithError(ctx, http.StatusBadRequest, err_msg)
+		}
+		results, err := node.DbFindDistinct(q, dField)
+		if err != nil {
+			err_msg := "err " + err.Error()
+			logger.Error(err_msg)
+			return responder.RespondWithError(ctx, http.StatusBadRequest, err_msg)
+		}
+		return responder.RespondWithData(ctx, results)
+	}
+
 	// defaults
 	order := "created_on"
 	direction := "-"

shock-server/node/db.go

@@ -38,6 +38,15 @@ func Initialize() {
 	}
 }
 
+func HasAttributeField(a string) bool {
+	for _, b := range strings.Split(conf.MONGODB_ATTRIBUTE_INDEXES, ",") {
+		if a == strings.TrimSpace(b) {
+			return true
+		}
+	}
+	return false
+}
+
 func dbDelete(q bson.M) (err error) {
 	session := db.Connection.Session.Copy()
 	defer session.Close()
@@ -77,6 +86,14 @@ func dbFind(q bson.M, results *Nodes, order string, options map[string]int) (cou
 	return
 }
 
+func DbFindDistinct(q bson.M, d string) (results interface{}, err error) {
+	session := db.Connection.Session.Copy()
+	defer session.Close()
+	c := session.DB(conf.MONGODB_DATABASE).C("Nodes")
+	err = c.Find(q).Distinct("attributes."+d, &results)
+	return
+}
+
 func Load(id string) (n *Node, err error) {
 	session := db.Connection.Session.Copy()
 	defer session.Close()