prevent empty query to be executed

executors.go

@@ -20,10 +20,16 @@ func (c *Connection) Reload(model interface{}) error {
 	})
 }
 
+// TODO: consider merging the following two methods.
+
 // Exec runs the given query.
 func (q *Query) Exec() error {
 	return q.Connection.timeFunc("Exec", func() error {
 		sql, args := q.ToSQL(nil)
+		if sql == "" {
+			return fmt.Errorf("empty query")
+		}
+
 		log(logging.SQL, sql, args...)
 		_, err := q.Connection.Store.Exec(sql, args...)
 		return err
@@ -36,6 +42,10 @@ func (q *Query) ExecWithCount() (int, error) {
 	count := int64(0)
 	return int(count), q.Connection.timeFunc("Exec", func() error {
 		sql, args := q.ToSQL(nil)
+		if sql == "" {
+			return fmt.Errorf("empty query")
+		}
+
 		log(logging.SQL, sql, args...)
 		result, err := q.Connection.Store.Exec(sql, args...)
 		if err != nil {

query.go

@@ -213,6 +213,10 @@ func Q(c *Connection) *Query {
 // from the `Model` passed in.
 func (q Query) ToSQL(model *Model, addColumns ...string) (string, []interface{}) {
 	sb := q.toSQLBuilder(model, addColumns...)
+	// nil model is allowed only when if RawSQL is provided.
+	if model == nil && (q.RawSQL == nil || q.RawSQL.Fragment == "") {
+		return "", nil
+	}
 	return sb.String(), sb.Args()
 }
 

query_test.go

@@ -386,3 +386,22 @@ func Test_ToSQL_RawQuery(t *testing.T) {
 		a.Equal(args, []interface{}{"random", "query"})
 	})
 }
+
+func Test_RawQuery_Empty(t *testing.T) {
+	Debug = true
+	defer func() { Debug = false }()
+
+	t.Run("EmptyQuery", func(t *testing.T) {
+		r := require.New(t)
+		transaction(func(tx *Connection) {
+			r.Error(tx.Q().Exec())
+		})
+	})
+
+	t.Run("EmptyRawQuery", func(t *testing.T) {
+		r := require.New(t)
+		transaction(func(tx *Connection) {
+			r.Error(tx.RawQuery("").Exec())
+		})
+	})
+}

sql_builder.go

@@ -17,6 +17,8 @@ type sqlBuilder struct {
 	AddColumns []string
 	sql        string
 	args       []interface{}
+	isCompiled bool
+	err        error
 }
 
 func newSQLBuilder(q Query, m *Model, addColumns ...string) *sqlBuilder {
@@ -25,6 +27,7 @@ func newSQLBuilder(q Query, m *Model, addColumns ...string) *sqlBuilder {
 		Model:      m,
 		AddColumns: addColumns,
 		args:       []interface{}{},
+		isCompiled: false,
 	}
 }
 
@@ -53,19 +56,15 @@ func hasLimitOrOffset(sqlString string) bool {
 }
 
 func (sq *sqlBuilder) String() string {
-	if sq.sql == "" {
+	if !sq.isCompiled {
 		sq.compile()
 	}
 	return sq.sql
 }
 
 func (sq *sqlBuilder) Args() []interface{} {
-	if len(sq.args) == 0 {
-		if len(sq.Query.RawSQL.Arguments) > 0 {
-			sq.args = sq.Query.RawSQL.Arguments
-		} else {
-			sq.compile()
-		}
+	if !sq.isCompiled {
+		sq.compile()
 	}
 	return sq.args
 }
@@ -83,7 +82,12 @@ func (sq *sqlBuilder) compile() {
 				}
 				sq.sql = sq.Query.RawSQL.Fragment
 			}
+			sq.args = sq.Query.RawSQL.Arguments
 		} else {
+			if sq.Model == nil {
+				sq.err = fmt.Errorf("sqlBuilder.compile() called but no RawSQL and Model specified")
+				return
+			}
 			switch sq.Query.Operation {
 			case Select:
 				sq.sql = sq.buildSelectSQL()