Merge pull request #6 from BrandonRoehl/single-transaction

Single transaction

.travis.yml

@@ -1,7 +1,7 @@
 language: go
 
 go:
-  - 1.11.x
+  - 1.13.x
   - master
 
 script:

dump.go

@@ -2,6 +2,7 @@ package mysqldump
 
 import (
 	"bytes"
+	"context"
 	"database/sql"
 	"errors"
 	"fmt"
@@ -14,9 +15,11 @@ import (
 /*
 Data struct to configure dump behavior
 
-    Out:          Stream to wite to
-    Connection:   Database connection to dump
-    IgnoreTables: Mark sensitive tables to ignore
+    Out:              Stream to wite to
+    Connection:       Database connection to dump
+    IgnoreTables:     Mark sensitive tables to ignore
+    MaxAllowedPacket: Sets the largest packet size to use in backups
+    LockTables:       Lock all tables for the duration of the dump
 */
 type Data struct {
 	Out              io.Writer
@@ -25,6 +28,7 @@ type Data struct {
 	MaxAllowedPacket int
 	LockTables       bool
 
+	tx         *sql.Tx
 	headerTmpl *template.Template
 	tableTmpl  *template.Template
 	footerTmpl *template.Template
@@ -123,11 +127,19 @@ func (data *Data) Dump() error {
 		data.MaxAllowedPacket = defaultMaxAllowedPacket
 	}
 
-	if err := meta.updateServerVersion(data.Connection); err != nil {
+	if err := data.getTemplates(); err != nil {
 		return err
 	}
 
-	if err := data.getTemplates(); err != nil {
+	// Start the read only transaction and defer the rollback until the end
+	// This way the database will have the exact state it did at the begining of
+	// the backup and nothing can be accidentally committed
+	if err := data.begin(); err != nil {
+		return err
+	}
+	defer data.rollback()
+
+	if err := meta.updateServerVersion(data); err != nil {
 		return err
 	}
 
@@ -173,6 +185,21 @@ func (data *Data) Dump() error {
 
 // MARK: - Private methods
 
+// begin starts a read only transaction that will be whatever the database was
+// when it was called
+func (data *Data) begin() (err error) {
+	data.tx, err = data.Connection.BeginTx(context.Background(), &sql.TxOptions{
+		Isolation: sql.LevelRepeatableRead,
+		ReadOnly:  true,
+	})
+	return
+}
+
+// rollback cancels the transaction
+func (data *Data) rollback() error {
+	return data.tx.Rollback()
+}
+
 // MARK: writter methods
 
 func (data *Data) dumpTable(name string) error {
@@ -214,7 +241,7 @@ func (data *Data) getTemplates() (err error) {
 func (data *Data) getTables() ([]string, error) {
 	tables := make([]string, 0)
 
-	rows, err := data.Connection.Query("SHOW TABLES")
+	rows, err := data.tx.Query("SHOW TABLES")
 	if err != nil {
 		return tables, err
 	}
@@ -241,10 +268,10 @@ func (data *Data) isIgnoredTable(name string) bool {
 	return false
 }
 
-func (data *metaData) updateServerVersion(db *sql.DB) (err error) {
+func (meta *metaData) updateServerVersion(data *Data) (err error) {
 	var serverVersion sql.NullString
-	err = db.QueryRow("SELECT version()").Scan(&serverVersion)
-	data.ServerVersion = serverVersion.String
+	err = data.tx.QueryRow("SELECT version()").Scan(&serverVersion)
+	meta.ServerVersion = serverVersion.String
 	return
 }
 
@@ -263,7 +290,7 @@ func (table *table) NameEsc() string {
 
 func (table *table) CreateSQL() (string, error) {
 	var tableReturn, tableSQL sql.NullString
-	if err := table.data.Connection.QueryRow("SHOW CREATE TABLE "+table.NameEsc()).Scan(&tableReturn, &tableSQL); err != nil {
+	if err := table.data.tx.QueryRow("SHOW CREATE TABLE "+table.NameEsc()).Scan(&tableReturn, &tableSQL); err != nil {
 		return "", err
 	}
 
@@ -274,13 +301,12 @@ func (table *table) CreateSQL() (string, error) {
 	return tableSQL.String, nil
 }
 
-// defer rows.Close()
 func (table *table) Init() (err error) {
 	if len(table.types) != 0 {
 		return errors.New("can't init twice")
 	}
 
-	table.rows, err = table.data.Connection.Query("SELECT * FROM " + table.NameEsc())
+	table.rows, err = table.data.tx.Query("SELECT * FROM " + table.NameEsc())
 	if err != nil {
 		return err
 	}
@@ -299,6 +325,7 @@ func (table *table) Init() (err error) {
 	}
 
 	table.types = make([]reflect.Type, len(tt))
+	table.values = make([]interface{}, len(tt))
 	for i, tp := range tt {
 		st := tp.ScanType()
 		if tp.DatabaseTypeName() == "BLOB" {
@@ -312,9 +339,6 @@ func (table *table) Init() (err error) {
 		} else {
 			table.types[i] = reflect.TypeOf(sql.NullString{})
 		}
-	}
-	table.values = make([]interface{}, len(tt))
-	for i := range table.values {
 		table.values[i] = reflect.New(table.types[i]).Interface()
 	}
 	return nil