Small performance improvements

Author: dancannon

query.go

@@ -83,15 +83,15 @@ func (t Term) build() (interface{}, error) {
 		}
 	}
 
-	args := []interface{}{}
-	optArgs := map[string]interface{}{}
+	args := make([]interface{}, len(t.args))
+	optArgs := make(map[string]interface{}, len(t.optArgs))
 
-	for _, v := range t.args {
+	for i, v := range t.args {
 		arg, err := v.build()
 		if err != nil {
 			return nil, err
 		}
-		args = append(args, arg)
+		args[i] = arg
 	}
 
 	for k, v := range t.optArgs {

utils.go

@@ -173,6 +173,10 @@ func optArgsToMap(optArgs OptArgs) map[string]interface{} {
 
 // Convert a list into a slice of terms
 func convertTermList(l []interface{}) termsList {
+	if len(l) == 0 {
+		return nil
+	}
+
 	terms := make(termsList, len(l))
 	for i, v := range l {
 		terms[i] = Expr(v)
@@ -183,6 +187,10 @@ func convertTermList(l []interface{}) termsList {
 
 // Convert a map into a map of terms
 func convertTermObj(o map[string]interface{}) termsObj {
+	if len(o) == 0 {
+		return nil
+	}
+
 	terms := make(termsObj, len(o))
 	for k, v := range o {
 		terms[k] = Expr(v)