database/sql: add option to use named parameter in query arguments

Modify the new Context methods to take a name-value driver struct.
This will require more modifications to drivers to use, but will
reduce the overall number of structures that need to be maintained
over time.

Fixes #12381

Change-Id: I30747533ce418a1be5991a0c8767a26e8451adbd
Reviewed-on: https://go-review.googlesource.com/30166
Reviewed-by: Brad Fitzpatrick <[email protected]>
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

Author: kardianos

src/database/sql/convert.go

@@ -21,8 +21,8 @@ var errNilPtr = errors.New("destination pointer is nil") // embedded in descript
 // Stmt.Query into driver Values.
 //
 // The statement ds may be nil, if no statement is available.
-func driverArgs(ds *driverStmt, args []interface{}) ([]driver.Value, error) {
-	dargs := make([]driver.Value, len(args))
+func driverArgs(ds *driverStmt, args []interface{}) ([]driver.NamedValue, error) {
+	nvargs := make([]driver.NamedValue, len(args))
 	var si driver.Stmt
 	if ds != nil {
 		si = ds.si
@@ -33,16 +33,27 @@ func driverArgs(ds *driverStmt, args []interface{}) ([]driver.Value, error) {
 	if !ok {
 		for n, arg := range args {
 			var err error
-			dargs[n], err = driver.DefaultParameterConverter.ConvertValue(arg)
+			nvargs[n].Ordinal = n + 1
+			if np, ok := arg.(NamedParam); ok {
+				arg = np.Value
+				nvargs[n].Name = np.Name
+			}
+			nvargs[n].Value, err = driver.DefaultParameterConverter.ConvertValue(arg)
+
 			if err != nil {
 				return nil, fmt.Errorf("sql: converting Exec argument #%d's type: %v", n, err)
 			}
 		}
-		return dargs, nil
+		return nvargs, nil
 	}
 
 	// Let the Stmt convert its own arguments.
 	for n, arg := range args {
+		nvargs[n].Ordinal = n + 1
+		if np, ok := arg.(NamedParam); ok {
+			arg = np.Value
+			nvargs[n].Name = np.Name
+		}
 		// First, see if the value itself knows how to convert
 		// itself to a driver type. For example, a NullString
 		// struct changing into a string or nil.
@@ -66,18 +77,18 @@ func driverArgs(ds *driverStmt, args []interface{}) ([]driver.Value, error) {
 		// same error.
 		var err error
 		ds.Lock()
-		dargs[n], err = cc.ColumnConverter(n).ConvertValue(arg)
+		nvargs[n].Value, err = cc.ColumnConverter(n).ConvertValue(arg)
 		ds.Unlock()
 		if err != nil {
 			return nil, fmt.Errorf("sql: converting argument #%d's type: %v", n, err)
 		}
-		if !driver.IsValue(dargs[n]) {
+		if !driver.IsValue(nvargs[n].Value) {
 			return nil, fmt.Errorf("sql: driver ColumnConverter error converted %T to unsupported type %T",
-				arg, dargs[n])
+				arg, nvargs[n].Value)
 		}
 	}
 
-	return dargs, nil
+	return nvargs, nil
 }
 
 // convertAssign copies to dest the value in src, converting it if possible.

src/database/sql/ctxutil.go

@@ -50,9 +50,13 @@ func ctxDriverPrepare(ctx context.Context, ci driver.Conn, query string) (driver
 	}
 }
 
-func ctxDriverExec(ctx context.Context, execer driver.Execer, query string, dargs []driver.Value) (driver.Result, error) {
+func ctxDriverExec(ctx context.Context, execer driver.Execer, query string, nvdargs []driver.NamedValue) (driver.Result, error) {
 	if execerCtx, is := execer.(driver.ExecerContext); is {
-		return execerCtx.ExecContext(ctx, query, dargs)
+		return execerCtx.ExecContext(ctx, query, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
 	}
 	if ctx.Done() == context.Background().Done() {
 		return execer.Exec(query, dargs)
@@ -90,9 +94,13 @@ func ctxDriverExec(ctx context.Context, execer driver.Execer, query string, darg
 	}
 }
 
-func ctxDriverQuery(ctx context.Context, queryer driver.Queryer, query string, dargs []driver.Value) (driver.Rows, error) {
+func ctxDriverQuery(ctx context.Context, queryer driver.Queryer, query string, nvdargs []driver.NamedValue) (driver.Rows, error) {
 	if queryerCtx, is := queryer.(driver.QueryerContext); is {
-		return queryerCtx.QueryContext(ctx, query, dargs)
+		return queryerCtx.QueryContext(ctx, query, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
 	}
 	if ctx.Done() == context.Background().Done() {
 		return queryer.Query(query, dargs)
@@ -130,9 +138,13 @@ func ctxDriverQuery(ctx context.Context, queryer driver.Queryer, query string, d
 	}
 }
 
-func ctxDriverStmtExec(ctx context.Context, si driver.Stmt, dargs []driver.Value) (driver.Result, error) {
+func ctxDriverStmtExec(ctx context.Context, si driver.Stmt, nvdargs []driver.NamedValue) (driver.Result, error) {
 	if siCtx, is := si.(driver.StmtExecContext); is {
-		return siCtx.ExecContext(ctx, dargs)
+		return siCtx.ExecContext(ctx, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
 	}
 	if ctx.Done() == context.Background().Done() {
 		return si.Exec(dargs)
@@ -170,9 +182,13 @@ func ctxDriverStmtExec(ctx context.Context, si driver.Stmt, dargs []driver.Value
 	}
 }
 
-func ctxDriverStmtQuery(ctx context.Context, si driver.Stmt, dargs []driver.Value) (driver.Rows, error) {
+func ctxDriverStmtQuery(ctx context.Context, si driver.Stmt, nvdargs []driver.NamedValue) (driver.Rows, error) {
 	if siCtx, is := si.(driver.StmtQueryContext); is {
-		return siCtx.QueryContext(ctx, dargs)
+		return siCtx.QueryContext(ctx, nvdargs)
+	}
+	dargs, err := namedValueToValue(nvdargs)
+	if err != nil {
+		return nil, err
 	}
 	if ctx.Done() == context.Background().Done() {
 		return si.Query(dargs)
@@ -253,3 +269,14 @@ func ctxDriverBegin(ctx context.Context, ci driver.Conn) (driver.Tx, error) {
 		return r.txi, r.err
 	}
 }
+
+func namedValueToValue(named []driver.NamedValue) ([]driver.Value, error) {
+	dargs := make([]driver.Value, len(named))
+	for n, param := range named {
+		if len(param.Name) > 0 {
+			return nil, errors.New("sql: driver does not support the use of Named Parameters")
+		}
+		dargs[n] = param.Value
+	}
+	return dargs, nil
+}

src/database/sql/driver/driver.go

@@ -24,6 +24,16 @@ import (
 //   time.Time
 type Value interface{}
 
+// NamedValue holds both the value name and value.
+// The Ordinal is the position of the parameter starting from one and is always set.
+// If the Name is not empty it should be used for the parameter identifier and
+// not the ordinal position.
+type NamedValue struct {
+	Name    string
+	Ordinal int
+	Value   Value
+}
+
 // Driver is the interface that must be implemented by a database
 // driver.
 type Driver interface {
@@ -71,7 +81,7 @@ type Execer interface {
 // ExecerContext is like execer, but must honor the context timeout and return
 // when the context is cancelled.
 type ExecerContext interface {
-	ExecContext(ctx context.Context, query string, args []Value) (Result, error)
+	ExecContext(ctx context.Context, query string, args []NamedValue) (Result, error)
 }
 
 // Queryer is an optional interface that may be implemented by a Conn.
@@ -88,7 +98,7 @@ type Queryer interface {
 // QueryerContext is like Queryer, but most honor the context timeout and return
 // when the context is cancelled.
 type QueryerContext interface {
-	QueryContext(ctx context.Context, query string, args []Value) (Rows, error)
+	QueryContext(ctx context.Context, query string, args []NamedValue) (Rows, error)
 }
 
 // Conn is a connection to a database. It is not used concurrently
@@ -174,13 +184,13 @@ type Stmt interface {
 // StmtExecContext enhances the Stmt interface by providing Exec with context.
 type StmtExecContext interface {
 	// ExecContext must honor the context timeout and return when it is cancelled.
-	ExecContext(ctx context.Context, args []Value) (Result, error)
+	ExecContext(ctx context.Context, args []NamedValue) (Result, error)
 }
 
 // StmtQueryContext enhances the Stmt interface by providing Query with context.
 type StmtQueryContext interface {
 	// QueryContext must honor the context timeout and return when it is cancelled.
-	QueryContext(ctx context.Context, args []Value) (Rows, error)
+	QueryContext(ctx context.Context, args []NamedValue) (Rows, error)
 }
 
 // ColumnConverter may be optionally implemented by Stmt if the