Add `Truncate` method (#2220)

This PR adds a `Truncate` method which allows to delete all existing rows in a table. The current `Delete` implementation enforces conditions to prevent accidental data deletion.

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/xorm/xorm/pulls/2220
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: KN4CK3R <kn4ck3r@noreply.gitea.io>
Co-committed-by: KN4CK3R <kn4ck3r@noreply.gitea.io>

engine.go

@@ -1233,12 +1233,21 @@ func (engine *Engine) Update(bean interface{}, condiBeans ...interface{}) (int64
 }
 
 // Delete records, bean's non-empty fields are conditions
+// At least one condition must be set.
 func (engine *Engine) Delete(beans ...interface{}) (int64, error) {
 	session := engine.NewSession()
 	defer session.Close()
 	return session.Delete(beans...)
 }
 
+// Truncate records, bean's non-empty fields are conditions
+// In contrast to Delete this method allows deletes without conditions.
+func (engine *Engine) Truncate(beans ...interface{}) (int64, error) {
+	session := engine.NewSession()
+	defer session.Close()
+	return session.Truncate(beans...)
+}
+
 // Get retrieve one record from table, bean's non-empty fields
 // are conditions
 func (engine *Engine) Get(beans ...interface{}) (bool, error) {

integrations/session_delete_test.go

@@ -208,7 +208,7 @@ func TestUnscopeDelete(t *testing.T) {
 	assert.NoError(t, err)
 	assert.EqualValues(t, 1, cnt)
 
-	var nowUnix = time.Now().Unix()
+	nowUnix := time.Now().Unix()
 	var s UnscopeDeleteStruct
 	cnt, err = testEngine.ID(1).Delete(&s)
 	assert.NoError(t, err)
@@ -266,3 +266,28 @@ func TestDelete2(t *testing.T) {
 	assert.NoError(t, err)
 	assert.False(t, has)
 }
+
+func TestTruncate(t *testing.T) {
+	assert.NoError(t, PrepareEngine())
+
+	type TruncateUser struct {
+		Uid int64 `xorm:"id pk not null autoincr"`
+	}
+
+	assert.NoError(t, testEngine.Sync(new(TruncateUser)))
+
+	cnt, err := testEngine.Insert(&TruncateUser{})
+	assert.NoError(t, err)
+	assert.EqualValues(t, 1, cnt)
+
+	_, err = testEngine.Delete(&TruncateUser{})
+	assert.Error(t, err)
+
+	_, err = testEngine.Truncate(&TruncateUser{})
+	assert.NoError(t, err)
+
+	user2 := TruncateUser{}
+	has, err := testEngine.ID(1).Get(&user2)
+	assert.NoError(t, err)
+	assert.False(t, has)
+}

interface.go

@@ -31,6 +31,7 @@ type Interface interface {
 	Decr(column string, arg ...interface{}) *Session
 	Desc(...string) *Session
 	Delete(...interface{}) (int64, error)
+	Truncate(...interface{}) (int64, error)
 	Distinct(columns ...string) *Session
 	DropIndexes(bean interface{}) error
 	Exec(sqlOrArgs ...interface{}) (sql.Result, error)

session_delete.go

@@ -91,7 +91,18 @@ func (session *Session) cacheDelete(table *schemas.Table, tableName, sqlStr stri
 }
 
 // Delete records, bean's non-empty fields are conditions
+// At least one condition must be set.
 func (session *Session) Delete(beans ...interface{}) (int64, error) {
+	return session.delete(beans, true)
+}
+
+// Truncate records, bean's non-empty fields are conditions
+// In contrast to Delete this method allows deletes without conditions.
+func (session *Session) Truncate(beans ...interface{}) (int64, error) {
+	return session.delete(beans, false)
+}
+
+func (session *Session) delete(beans []interface{}, mustHaveConditions bool) (int64, error) {
 	if session.isAutoClose {
 		defer session.Close()
 	}
@@ -127,7 +138,7 @@ func (session *Session) Delete(beans ...interface{}) (int64, error) {
 	}
 
 	pLimitN := session.statement.LimitN
-	if condWriter.Len() == 0 && (pLimitN == nil || *pLimitN == 0) {
+	if mustHaveConditions && condWriter.Len() == 0 && (pLimitN == nil || *pLimitN == 0) {
 		return 0, ErrNeedDeletedCond
 	}