// Begin2 should not be used by anything other than tests.
// It will eventually replace Begin, but it breaks compatibility with older clients.
// Once all clients are upgraded, it can be replaced.
func (sq *SqlQuery) Begin2(ctx context.Context, beginRequest *proto.BeginRequest, beginResponse *proto.BeginResponse) (err error) {
	defer sq.server.HandlePanic(&err)
	session := &proto.Session{
		SessionId: beginRequest.SessionId,
	}
	txInfo := new(proto.TransactionInfo)
	tErr := sq.server.Begin(callinfo.RPCWrapCallInfo(ctx), session, txInfo)
	// Convert from TxInfo => beginResponse for the output
	beginResponse.TransactionId = txInfo.TransactionId
	tabletserver.AddTabletErrorToBeginResponse(tErr, beginResponse)
	if *tabletserver.RPCErrorOnlyInReply {
		return nil
	}
	return tErr
}

// Begin2 should not be used by anything other than tests.
// It will eventually replace Begin, but it breaks compatibility with older clients.
// Once all clients are upgraded, it can be replaced.
func (sq *SqlQuery) Begin2(ctx context.Context, beginRequest *proto.BeginRequest, beginResponse *proto.BeginResponse) (err error) {
	defer sq.server.HandlePanic(&err)
	session := &proto.Session{
		SessionId: beginRequest.SessionId,
	}
	txInfo := new(proto.TransactionInfo)
	ctx = callerid.NewContext(ctx,
		callerid.GoRPCEffectiveCallerID(beginRequest.EffectiveCallerID),
		callerid.GoRPCImmediateCallerID(beginRequest.ImmediateCallerID),
	)
	tErr := sq.server.Begin(callinfo.RPCWrapCallInfo(ctx), proto.TargetToProto3(beginRequest.Target), session, txInfo)
	// Convert from TxInfo => beginResponse for the output
	beginResponse.TransactionId = txInfo.TransactionId
	tabletserver.AddTabletError(tErr, &beginResponse.Err)
	return nil
}

// AddTabletErrorToBeginResponse will mutate a BeginResponse struct to fill in the Err
// field with details from the TabletError.
func AddTabletErrorToBeginResponse(err error, reply *proto.BeginResponse) {
	if err == nil {
		return
	}
	reply.Err = rpcErrFromTabletError(err)
}