feat: add tx methods to IDB (#587)

db.go

@@ -2,7 +2,9 @@ package bun
 
 import (
 	"context"
+	"crypto/rand"
 	"database/sql"
+	"encoding/hex"
 	"fmt"
 	"reflect"
 	"strings"
@@ -431,6 +433,8 @@ func (db *DB) PrepareContext(ctx context.Context, query string) (Stmt, error) {
 type Tx struct {
 	ctx context.Context
 	db  *DB
+	// name is the name of a savepoint
+	name string
 	*sql.Tx
 }
 
@@ -479,19 +483,51 @@ func (db *DB) BeginTx(ctx context.Context, opts *sql.TxOptions) (Tx, error) {
 }
 
 func (tx Tx) Commit() error {
+	if tx.name == "" {
+		return tx.commitTX()
+	}
+	return tx.commitSP()
+}
+
+func (tx Tx) commitTX() error {
 	ctx, event := tx.db.beforeQuery(tx.ctx, nil, "COMMIT", nil, "COMMIT", nil)
 	err := tx.Tx.Commit()
 	tx.db.afterQuery(ctx, event, nil, err)
 	return err
 }
 
+func (tx Tx) commitSP() error {
+	if tx.Dialect().Features().Has(feature.MSSavepoint) {
+		return nil
+	}
+	query := "RELEASE SAVEPOINT " + tx.name
+	_, err := tx.ExecContext(tx.ctx, query)
+	return err
+}
+
 func (tx Tx) Rollback() error {
+	if tx.name == "" {
+		return tx.rollbackTX()
+	}
+	return tx.rollbackSP()
+}
+
+func (tx Tx) rollbackTX() error {
 	ctx, event := tx.db.beforeQuery(tx.ctx, nil, "ROLLBACK", nil, "ROLLBACK", nil)
 	err := tx.Tx.Rollback()
 	tx.db.afterQuery(ctx, event, nil, err)
 	return err
 }
 
+func (tx Tx) rollbackSP() error {
+	query := "ROLLBACK TO SAVEPOINT " + tx.name
+	if tx.Dialect().Features().Has(feature.MSSavepoint) {
+		query = "ROLLBACK TRANSACTION " + tx.name
+	}
+	_, err := tx.ExecContext(tx.ctx, query)
+	return err
+}
+
 func (tx Tx) Exec(query string, args ...interface{}) (sql.Result, error) {
 	return tx.ExecContext(context.TODO(), query, args...)
 }
@@ -534,6 +570,60 @@ func (tx Tx) QueryRowContext(ctx context.Context, query string, args ...interfac
 
 //------------------------------------------------------------------------------
 
+func (tx Tx) Begin() (Tx, error) {
+	return tx.BeginTx(tx.ctx, nil)
+}
+
+// BeginTx will save a point in the running transaction.
+func (tx Tx) BeginTx(ctx context.Context, _ *sql.TxOptions) (Tx, error) {
+	// mssql savepoint names are limited to 32 characters
+	sp := make([]byte, 14)
+	_, err := rand.Read(sp)
+	if err != nil {
+		return Tx{}, err
+	}
+
+	qName := "SP_" + hex.EncodeToString(sp)
+	query := "SAVEPOINT " + qName
+	if tx.Dialect().Features().Has(feature.MSSavepoint) {
+		query = "SAVE TRANSACTION " + qName
+	}
+	_, err = tx.ExecContext(ctx, query)
+	if err != nil {
+		return Tx{}, err
+	}
+	return Tx{
+		ctx:  ctx,
+		db:   tx.db,
+		Tx:   tx.Tx,
+		name: qName,
+	}, nil
+}
+
+func (tx Tx) RunInTx(
+	ctx context.Context, _ *sql.TxOptions, fn func(ctx context.Context, tx Tx) error,
+) error {
+	sp, err := tx.BeginTx(ctx, nil)
+	if err != nil {
+		return err
+	}
+
+	var done bool
+
+	defer func() {
+		if !done {
+			_ = sp.Rollback()
+		}
+	}()
+
+	if err := fn(ctx, sp); err != nil {
+		return err
+	}
+
+	done = true
+	return sp.Commit()
+}
+
 func (tx Tx) Dialect() schema.Dialect {
 	return tx.db.Dialect()
 }

dialect/feature/feature.go

@@ -29,4 +29,5 @@ const (
 	OffsetFetch
 	SelectExists
 	UpdateFromTable
+	MSSavepoint
 )

dialect/mssqldialect/dialect.go

@@ -46,7 +46,8 @@ func New() *Dialect {
 		feature.Identity |
 		feature.Output |
 		feature.OffsetFetch |
-		feature.UpdateFromTable
+		feature.UpdateFromTable |
+		feature.MSSavepoint
 	return d
 }
 

internal/dbtest/db_test.go

@@ -271,6 +271,7 @@ func TestDB(t *testing.T) {
 		{testEmbedModelPointer},
 		{testJSONMarshaler},
 		{testNilDriverValue},
+		{testRunInTxAndSavepoint},
 	}
 
 	testEachDB(t, func(t *testing.T, dbName string, db *bun.DB) {
@@ -1401,3 +1402,99 @@ func testNilDriverValue(t *testing.T, db *bun.DB) {
 	_, err = db.NewInsert().Model(&Model{Value: &DriverValue{s: "hello"}}).Exec(ctx)
 	require.NoError(t, err)
 }
+
+func testRunInTxAndSavepoint(t *testing.T, db *bun.DB) {
+	type Counter struct {
+		Count int64
+	}
+
+	err := db.ResetModel(ctx, (*Counter)(nil))
+	require.NoError(t, err)
+
+	_, err = db.NewInsert().Model(&Counter{Count: 0}).Exec(ctx)
+	require.NoError(t, err)
+
+	err = db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
+		err := tx.RunInTx(ctx, nil, func(ctx context.Context, sp bun.Tx) error {
+			_, err := sp.NewUpdate().Model((*Counter)(nil)).
+				Set("count = count + 1").
+				Where("1 = 1").
+				Exec(ctx)
+			return err
+		})
+		require.NoError(t, err)
+		// rolling back the transaction should rollback what happened inside savepoint
+		return errors.New("fake error")
+	})
+	require.Error(t, err)
+
+	var count int
+	err = db.NewSelect().Model((*Counter)(nil)).Scan(ctx, &count)
+	require.NoError(t, err)
+	require.Equal(t, 0, count)
+
+	err = db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
+		err := tx.RunInTx(ctx, nil, func(ctx context.Context, sp bun.Tx) error {
+			_, err := sp.NewInsert().Model(&Counter{Count: 1}).
+				Exec(ctx)
+			require.NoError(t, err)
+			return err
+		})
+		require.NoError(t, err)
+
+		// ignored on purpose this error
+		// rolling back a savepoint should not affect the transaction
+		// nor other savepoints on the same level
+		_ = tx.RunInTx(ctx, nil, func(ctx context.Context, sp bun.Tx) error {
+			_, err := sp.NewInsert().Model(&Counter{Count: 2}).
+				Exec(ctx)
+			require.NoError(t, err)
+			return errors.New("fake error")
+		})
+
+		return err
+	})
+	require.NoError(t, err)
+
+	count, err = db.NewSelect().Model((*Counter)(nil)).Count(ctx)
+	require.NoError(t, err)
+	require.Equal(t, 2, count)
+
+	err = db.ResetModel(ctx, (*Counter)(nil))
+	require.NoError(t, err)
+
+	// happy path, commit transaction, savepoints and sub-savepoints
+	err = db.RunInTx(ctx, nil, func(ctx context.Context, tx bun.Tx) error {
+		_, err := tx.NewInsert().Model(&Counter{Count: 1}).
+			Exec(ctx)
+		require.NoError(t, err)
+
+		err = tx.RunInTx(ctx, nil, func(ctx context.Context, sp bun.Tx) error {
+			_, err := sp.NewInsert().Model(&Counter{Count: 1}).
+				Exec(ctx)
+			if err != nil {
+				return err
+			}
+
+			return sp.RunInTx(ctx, nil, func(ctx context.Context, subSp bun.Tx) error {
+				_, err := subSp.NewInsert().Model(&Counter{Count: 1}).
+					Exec(ctx)
+				return err
+			})
+		})
+		require.NoError(t, err)
+
+		err = tx.RunInTx(ctx, nil, func(ctx context.Context, sp bun.Tx) error {
+			_, err := sp.NewInsert().Model(&Counter{Count: 2}).
+				Exec(ctx)
+			return err
+		})
+
+		return err
+	})
+	require.NoError(t, err)
+
+	count, err = db.NewSelect().Model((*Counter)(nil)).Count(ctx)
+	require.NoError(t, err)
+	require.Equal(t, 4, count)
+}

query_base.go

@@ -57,6 +57,9 @@ type IDB interface {
 	NewTruncateTable() *TruncateTableQuery
 	NewAddColumn() *AddColumnQuery
 	NewDropColumn() *DropColumnQuery
+
+	BeginTx(ctx context.Context, opts *sql.TxOptions) (Tx, error)
+	RunInTx(ctx context.Context, opts *sql.TxOptions, f func(ctx context.Context, tx Tx) error) error
 }
 
 var (