qb: update, delete and performance improvements

qb/mock.go

@@ -0,0 +1,14 @@
+package qb
+
+import "bytes"
+
+type mockExpr struct {
+	cql   string
+	names []string
+}
+
+func (m mockExpr) WriteCql(cql *bytes.Buffer) (names []string) {
+	cql.WriteString(m.cql)
+	names = m.names
+	return
+}