make savepoint syntax configurable

.travis.yml

@@ -1,9 +1,7 @@
 language: go
 go:
-  - 1.8.x
-  - 1.9.x
-  - 1.10.x
-  - 1.11.x
+  # older versions are not tested, due to SQL driver compatibility
+  - 1.12.x
 
 services:
   - mysql

Makefile

@@ -29,7 +29,7 @@ ifndef CI
 	MYSQLCMD=docker-compose exec mysql mysql
 endif
 
-PSQLCMD=psql 
+PSQLCMD=psql
 ifndef CI
 	PSQLCMD=docker-compose exec postgres psql
 endif

db.go

@@ -57,8 +57,6 @@ import (
 	"database/sql/driver"
 	"fmt"
 	"io"
-	"math/rand"
-	"strconv"
 	"sync"
 )
 
@@ -67,8 +65,13 @@ import (
 // connection.
 //
 // When Open is called any number of times it returns
-// the same transaction connection. Any Begin, Commit calls
-// will not start or close the transaction.
+// the same transaction connection.
+//
+// Any Begin, Commit calls will not start or close the transaction.
+// Instead the savepoint will be created, released or rolled back.
+// In case if your SQL driver does not support save points - use nil
+// for the SavePointOption argument. If driver has non default
+// save point logic, you can override the default with SavePointOption.
 //
 // When Close is called, the transaction is rolled back.
 //
@@ -80,28 +83,32 @@ import (
 // Note: if you open a secondary database, make sure to differianciate
 // the dsn string when opening the sql.DB. The transaction will be
 // isolated within that dsn
-func Register(name, drv, dsn string) {
+func Register(name, drv, dsn string, options ...func(*conn) error) {
 	sql.Register(name, &txDriver{
-		dsn:   dsn,
-		drv:   drv,
-		conns: make(map[string]*conn),
+		dsn:     dsn,
+		drv:     drv,
+		conns:   make(map[string]*conn),
+		options: options,
 	})
 }
 
 // txDriver is an sql driver which runs on single transaction
 // when the Close is called, transaction is rolled back
 type conn struct {
 	sync.Mutex
-	tx     *sql.Tx
-	dsn    string
-	opened uint
-	drv    *txDriver
+	tx        *sql.Tx
+	dsn       string
+	opened    uint
+	drv       *txDriver
+	saves     uint
+	savePoint SavePoint
 }
 
 type txDriver struct {
 	sync.Mutex
-	db    *sql.DB
-	conns map[string]*conn
+	db      *sql.DB
+	conns   map[string]*conn
+	options []func(*conn) error
 
 	drv string
 	dsn string
@@ -121,7 +128,13 @@ func (d *txDriver) Open(dsn string) (driver.Conn, error) {
 	}
 	c, ok := d.conns[dsn]
 	if !ok {
-		c = &conn{dsn: dsn, drv: d}
+		c = &conn{dsn: dsn, drv: d, savePoint: &defaultSavePoint{}}
+		for _, opt := range d.options {
+			if e := opt(c); e != nil {
+				return c, e
+			}
+		}
+
 		c.tx, err = d.db.Begin()
 		d.conns[dsn] = c
 	}
@@ -151,30 +164,43 @@ type tx struct {
 }
 
 func (c *conn) Begin() (driver.Tx, error) {
+	if c.savePoint == nil {
+		return &tx{"_", c}, nil // save point is not supported
+	}
+
 	c.Lock()
 	defer c.Unlock()
 
-	id := "tx_" + strconv.Itoa(rand.Int())
-	_, err := c.tx.Exec(fmt.Sprintf(`SAVEPOINT %s`, id))
+	c.saves++
+	id := fmt.Sprintf("tx_%d", c.saves)
+	_, err := c.tx.Exec(c.savePoint.Create(id))
 	if err != nil {
 		return nil, err
 	}
 	return &tx{id, c}, nil
 }
 
 func (tx *tx) Commit() error {
+	if tx.conn.savePoint == nil {
+		return nil // save point is not supported
+	}
+
 	tx.conn.Lock()
 	defer tx.conn.Unlock()
 
-	_, err := tx.conn.tx.Exec(fmt.Sprintf(`RELEASE SAVEPOINT %s`, tx.id))
+	_, err := tx.conn.tx.Exec(tx.conn.savePoint.Release(tx.id))
 	return err
 }
 
 func (tx *tx) Rollback() error {
+	if tx.conn.savePoint == nil {
+		return nil // save point is not supported
+	}
+
 	tx.conn.Lock()
 	defer tx.conn.Unlock()
 
-	_, err := tx.conn.tx.Exec(fmt.Sprintf(`ROLLBACK TO SAVEPOINT %s`, tx.id))
+	_, err := tx.conn.tx.Exec(tx.conn.savePoint.Rollback(tx.id))
 	return err
 }
 

go.mod

@@ -1,9 +1,3 @@
 module github.com/DATA-DOG/go-txdb
 
 go 1.12
-
-require (
-	github.com/go-sql-driver/mysql v1.4.1
-	github.com/lib/pq v1.1.1
-	google.golang.org/appengine v1.6.1 // indirect
-)

options.go

@@ -0,0 +1,34 @@
+package txdb
+
+import "fmt"
+
+// SavePoint defines the syntax to create savepoints
+// within transaction
+type SavePoint interface {
+	Create(id string) string
+	Release(id string) string
+	Rollback(id string) string
+}
+
+type defaultSavePoint struct{}
+
+func (dsp *defaultSavePoint) Create(id string) string {
+	return fmt.Sprintf("SAVEPOINT %s", id)
+}
+func (dsp *defaultSavePoint) Release(id string) string {
+	return fmt.Sprintf("RELEASE SAVEPOINT %s", id)
+}
+func (dsp *defaultSavePoint) Rollback(id string) string {
+	return fmt.Sprintf("ROLLBACK TO SAVEPOINT %s", id)
+}
+
+// SavePointOption allows to modify the logic for
+// transaction save points. In such cases if your driver
+// does not support it, use nil. If not compatible with default
+// use custom.
+func SavePointOption(savePoint SavePoint) func(*conn) error {
+	return func(c *conn) error {
+		c.savePoint = savePoint
+		return nil
+	}
+}