quicker SPOP

Author: alicebob

cmd_set.go

@@ -400,12 +400,14 @@ func (m *Miniredis) cmdSpop(c *server.Peer, cmd string, args []string) {
 		}
 
 		var deleted []string
+		members := db.setMembers(opts.key)
 		for i := 0; i < opts.count; i++ {
-			members := db.setMembers(opts.key)
 			if len(members) == 0 {
 				break
 			}
-			member := members[m.randIntn(len(members))]
+			i := m.randIntn(len(members))
+			member := members[i]
+			members = delElem(members, i)
 			db.setRem(opts.key, member)
 			deleted = append(deleted, member)
 		}
@@ -702,3 +704,12 @@ func (m *Miniredis) cmdSscan(c *server.Peer, cmd string, args []string) {
 
 	})
 }
+
+func delElem(ls []string, i int) []string {
+	// this swap+truncate is faster but changes behaviour:
+	// ls[i] = ls[len(ls)-1]
+	// ls = ls[:len(ls)-1]
+	// so we do the dumb thing:
+	ls = append(ls[:i], ls[i+1:]...)
+	return ls
+}

cmd_set_test.go

@@ -870,3 +870,10 @@ func TestSscan(t *testing.T) {
 		),
 	)
 }
+
+func TestDelElem(t *testing.T) {
+	equals(t, []string{"b", "c", "d"}, delElem([]string{"a", "b", "c", "d"}, 0))
+	equals(t, []string{"a", "c", "d"}, delElem([]string{"a", "b", "c", "d"}, 1))
+	equals(t, []string{"a", "b", "d"}, delElem([]string{"a", "b", "c", "d"}, 2))
+	equals(t, []string{"a", "b", "c"}, delElem([]string{"a", "b", "c", "d"}, 3))
+}