Automatically reprepare statements on error 1615

AUTHORS

@@ -50,6 +50,7 @@ Jeffrey Charles <jeffreycharles at gmail.com>
 Jerome Meyer <jxmeyer at gmail.com>
 Jiajia Zhong <zhong2plus at gmail.com>
 Jian Zhen <zhenjl at gmail.com>
+Joseph Boudou <joseph.boudou@matabio.net>
 Joshua Prunier <joshua.prunier at gmail.com>
 Julien Lefevre <julien.lefevr at gmail.com>
 Julien Schmidt <go-sql-driver at julienschmidt.com>

README.md

@@ -175,6 +175,14 @@ Default:        false
 ```
 `allowOldPasswords=true` allows the usage of the insecure old password method. This should be avoided, but is necessary in some cases. See also [the old_passwords wiki page](https://github.com/go-sql-driver/mysql/wiki/old_passwords).
 
+##### `autoReprepare`
+
+```
+Type:           decimal number
+Default:        0
+```
+When `autoReprepare` is greater than zero, the driver will re-prepare statements when error 1615 is received from the database. Some known bugs of MySQL and MariaDB spuriously invalidate prepared statements, resulting in this error being sent. This parameter is meant to workaround these bugs. More precisely, the value of `autoReprepare` indicates how many successive errors 1615 are handled before the execution of the statement fails; hence, it should not be greater than one.
+
 ##### `charset`
 
 ```

connection.go

@@ -177,6 +177,9 @@ func (mc *mysqlConn) Prepare(query string) (driver.Stmt, error) {
 	stmt := &mysqlStmt{
 		mc: mc,
 	}
+	if stmt.mc.cfg.AutoReprepare > 0 {
+		stmt.queryStr = query
+	}
 
 	// Read Result
 	columnCount, err := stmt.readPrepareResultPacket()

dsn.go

@@ -55,6 +55,7 @@ type Config struct {
 	AllowCleartextPasswords bool // Allows the cleartext client side plugin
 	AllowNativePasswords    bool // Allows the native password authentication method
 	AllowOldPasswords       bool // Allows the old insecure password method
+	AutoReprepare           int  // Automatically reprepare statements when receiving error 1615
 	CheckConnLiveness       bool // Check connections for liveness before using them
 	ClientFoundRows         bool // Return number of matching rows instead of rows changed
 	ColumnsWithAlias        bool // Prepend table alias to column names
@@ -212,6 +213,10 @@ func (cfg *Config) FormatDSN() string {
 		writeDSNParam(&buf, &hasParam, "allowOldPasswords", "true")
 	}
 
+	if cfg.AutoReprepare > 0 {
+		writeDSNParam(&buf, &hasParam, "autoReprepare", strconv.Itoa(cfg.AutoReprepare))
+	}
+
 	if !cfg.CheckConnLiveness {
 		writeDSNParam(&buf, &hasParam, "checkConnLiveness", "false")
 	}
@@ -407,6 +412,13 @@ func parseDSNParams(cfg *Config, params string) (err error) {
 				return errors.New("invalid bool value: " + value)
 			}
 
+		// Reprepare statement on error 1615
+		case "autoReprepare":
+			cfg.AutoReprepare, err = strconv.Atoi(value)
+			if err != nil {
+				return err
+			}
+
 		// Check connections for Liveness before using them
 		case "checkConnLiveness":
 			var isBool bool

dsn_test.go

@@ -44,6 +44,9 @@ var testDSNs = []struct {
 }, {
 	"user:password@/dbname?allowNativePasswords=false&checkConnLiveness=false&maxAllowedPacket=0",
 	&Config{User: "user", Passwd: "password", Net: "tcp", Addr: "127.0.0.1:3306", DBName: "dbname", Collation: "utf8mb4_general_ci", Loc: time.UTC, MaxAllowedPacket: 0, AllowNativePasswords: false, CheckConnLiveness: false},
+}, {
+	"username:password@protocol(address)/dbname?autoReprepare=2",
+	&Config{User: "username", Passwd: "password", Net: "protocol", Addr: "address", DBName: "dbname", Collation: "utf8mb4_general_ci", Loc: time.UTC, MaxAllowedPacket: defaultMaxAllowedPacket, AllowNativePasswords: true, AutoReprepare: 2, CheckConnLiveness: true},
 }, {
 	"user:p@ss(word)@tcp([de:ad:be:ef::ca:fe]:80)/dbname?loc=Local",
 	&Config{User: "user", Passwd: "p@ss(word)", Net: "tcp", Addr: "[de:ad:be:ef::ca:fe]:80", DBName: "dbname", Collation: "utf8mb4_general_ci", Loc: time.Local, MaxAllowedPacket: defaultMaxAllowedPacket, AllowNativePasswords: true, CheckConnLiveness: true},

statement.go

@@ -20,6 +20,8 @@ type mysqlStmt struct {
 	mc         *mysqlConn
 	id         uint32
 	paramCount int
+	queryStr   string
+	reprepared int // How many times the statement has been reprepared since last execution.
 }
 
 func (stmt *mysqlStmt) Close() error {
@@ -68,8 +70,16 @@ func (stmt *mysqlStmt) Exec(args []driver.Value) (driver.Result, error) {
 	// Read Result
 	resLen, err := mc.readResultSetHeaderPacket()
 	if err != nil {
+		if mysqlErr, ok := err.(*MySQLError); ok && stmt.reprepared < stmt.mc.cfg.AutoReprepare &&
+			mysqlErr.Number == 1615 {
+			err = stmt.reprepare()
+			if err == nil {
+				return stmt.Exec(args)
+			}
+		}
 		return nil, err
 	}
+	stmt.reprepared = 0
 
 	if resLen > 0 {
 		// Columns
@@ -113,8 +123,16 @@ func (stmt *mysqlStmt) query(args []driver.Value) (*binaryRows, error) {
 	// Read Result
 	resLen, err := mc.readResultSetHeaderPacket()
 	if err != nil {
+		if mysqlErr, ok := err.(*MySQLError); ok && stmt.reprepared < stmt.mc.cfg.AutoReprepare &&
+			mysqlErr.Number == 1615 {
+			err = stmt.reprepare()
+			if err == nil {
+				return stmt.query(args)
+			}
+		}
 		return nil, err
 	}
+	stmt.reprepared = 0
 
 	rows := new(binaryRows)
 
@@ -135,6 +153,40 @@ func (stmt *mysqlStmt) query(args []driver.Value) (*binaryRows, error) {
 	return rows, err
 }
 
+func (stmt *mysqlStmt) reprepare() error {
+	stmt.reprepared += 1
+
+	// Close
+	err := stmt.mc.writeCommandPacketUint32(comStmtClose, stmt.id)
+	if err != nil {
+		return err
+	}
+	stmt.id = 0
+	stmt.paramCount = 0
+
+	// Send prepare
+	err = stmt.mc.writeCommandPacketStr(comStmtPrepare, stmt.queryStr)
+	if err != nil {
+		return err
+	}
+
+	// Read Result
+	columnCount, err := stmt.readPrepareResultPacket()
+	if err == nil {
+		if stmt.paramCount > 0 {
+			if err = stmt.mc.readUntilEOF(); err != nil {
+				return err
+			}
+		}
+
+		if columnCount > 0 {
+			err = stmt.mc.readUntilEOF()
+		}
+	}
+
+	return err
+}
+
 var jsonType = reflect.TypeOf(json.RawMessage{})
 
 type converter struct{}