spanner/transaction_test.go - gocloud - Git at Google

 /*
 Copyright 2017 Google LLC

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

 package spanner

 import (
 	"context"
 	"errors"
 	"fmt"
 	"reflect"
 	"sync"
 	"testing"
 	"time"

 	"cloud.google.com/go/spanner/internal/testutil"
 	sppb "google.golang.org/genproto/googleapis/spanner/v1"
 	"google.golang.org/grpc/codes"
 	gstatus "google.golang.org/grpc/status"
 )

 // Single can only be used once.
 func TestSingle(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 	server, client := newSpannerInMemTestServer(t)
 	defer server.teardown(client)

 	txn := client.Single()
 	defer txn.Close()
 	_, _, e := txn.acquire(ctx)
 	if e != nil {
 		t.Fatalf("Acquire for single use, got %v, want nil.", e)
 	}
 	_, _, e = txn.acquire(ctx)
 	if wantErr := errTxClosed(); !testEqual(e, wantErr) {
 		t.Fatalf("Second acquire for single use, got %v, want %v.", e, wantErr)
 	}

 	// Only one CreateSessionRequest is sent.
 	if _, err := shouldHaveReceived(server.testSpanner, []interface{}{&sppb.CreateSessionRequest{}}); err != nil {
 		t.Fatal(err)
 	}
 }

 // Re-using ReadOnlyTransaction: can recover from acquire failure.
 func TestReadOnlyTransaction_RecoverFromFailure(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 	server, client := newSpannerInMemTestServer(t)
 	defer server.teardown(client)

 	txn := client.ReadOnlyTransaction()
 	defer txn.Close()

 	// First request will fail.
 	errUsr := gstatus.Error(codes.Unknown, "error")
 	server.testSpanner.PutExecutionTime(testutil.MethodBeginTransaction,
 		testutil.SimulatedExecutionTime{
 			Errors: []error{errUsr},
 		})

 	_, _, e := txn.acquire(ctx)
 	if wantErr := toSpannerError(errUsr); !testEqual(e, wantErr) {
 		t.Fatalf("Acquire for multi use, got %v, want %v.", e, wantErr)
 	}
 	_, _, e = txn.acquire(ctx)
 	if e != nil {
 		t.Fatalf("Acquire for multi use, got %v, want nil.", e)
 	}
 }

 // ReadOnlyTransaction: can not be used after close.
 func TestReadOnlyTransaction_UseAfterClose(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 	server, client := newSpannerInMemTestServer(t)
 	defer server.teardown(client)

 	txn := client.ReadOnlyTransaction()
 	txn.Close()

 	_, _, e := txn.acquire(ctx)
 	if wantErr := errTxClosed(); !testEqual(e, wantErr) {
 		t.Fatalf("Second acquire for multi use, got %v, want %v.", e, wantErr)
 	}
 }

 // ReadOnlyTransaction: can be acquired concurrently.
 func TestReadOnlyTransaction_Concurrent(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 	server, client := newSpannerInMemTestServer(t)
 	defer server.teardown(client)
 	txn := client.ReadOnlyTransaction()
 	defer txn.Close()

 	server.testSpanner.Freeze()
 	var (
 		sh1 *sessionHandle
 		sh2 *sessionHandle
 		ts1 *sppb.TransactionSelector
 		ts2 *sppb.TransactionSelector
 		wg  = sync.WaitGroup{}
 	)
 	acquire := func(sh **sessionHandle, ts **sppb.TransactionSelector) {
 		defer wg.Done()
 		var e error
 		*sh, *ts, e = txn.acquire(ctx)
 		if e != nil {
 			t.Errorf("Concurrent acquire for multiuse, got %v, expect nil.", e)
 		}
 	}
 	wg.Add(2)
 	go acquire(&sh1, &ts1)
 	go acquire(&sh2, &ts2)

 	// TODO(deklerk): Get rid of this.
 	<-time.After(100 * time.Millisecond)

 	server.testSpanner.Unfreeze()
 	wg.Wait()
 	if sh1.session.id != sh2.session.id {
 		t.Fatalf("Expected acquire to get same session handle, got %v and %v.", sh1, sh2)
 	}
 	if !testEqual(ts1, ts2) {
 		t.Fatalf("Expected acquire to get same transaction selector, got %v and %v.", ts1, ts2)
 	}
 }

 func TestApply_Single(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 	server, client := newSpannerInMemTestServer(t)
 	defer server.teardown(client)

 	ms := []*Mutation{
 		Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(1), "Foo", int64(50)}),
 		Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(2), "Bar", int64(1)}),
 	}
 	if _, e := client.Apply(ctx, ms, ApplyAtLeastOnce()); e != nil {
 		t.Fatalf("applyAtLeastOnce retry on abort, got %v, want nil.", e)
 	}

 	if _, err := shouldHaveReceived(server.testSpanner, []interface{}{
 		&sppb.CreateSessionRequest{},
 		&sppb.CommitRequest{},
 	}); err != nil {
 		t.Fatal(err)
 	}
 }

 // Transaction retries on abort.
 func TestApply_RetryOnAbort(t *testing.T) {
 	ctx := context.Background()
 	t.Parallel()
 	server, client := newSpannerInMemTestServer(t)
 	defer server.teardown(client)

 	// First commit will fail, and the retry will begin a new transaction.
 	errAbrt := spannerErrorf(codes.Aborted, "")
 	server.testSpanner.PutExecutionTime(testutil.MethodCommitTransaction,
 		testutil.SimulatedExecutionTime{
 			Errors: []error{errAbrt},
 		})

 	ms := []*Mutation{
 		Insert("Accounts", []string{"AccountId"}, []interface{}{int64(1)}),
 	}

 	if _, e := client.Apply(ctx, ms); e != nil {
 		t.Fatalf("ReadWriteTransaction retry on abort, got %v, want nil.", e)
 	}

 	if _, err := shouldHaveReceived(server.testSpanner, []interface{}{
 		&sppb.CreateSessionRequest{},
 		&sppb.BeginTransactionRequest{},
 		&sppb.CommitRequest{}, // First commit fails.
 		&sppb.BeginTransactionRequest{},
 		&sppb.CommitRequest{}, // Second commit succeeds.
 	}); err != nil {
 		t.Fatal(err)
 	}
 }

 // Tests that NotFound errors cause failures, and aren't retried.
 func TestTransaction_NotFound(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 	server, client := newSpannerInMemTestServer(t)
 	defer server.teardown(client)

 	wantErr := spannerErrorf(codes.NotFound, "Session not found")
 	server.testSpanner.PutExecutionTime(testutil.MethodBeginTransaction,
 		testutil.SimulatedExecutionTime{
 			Errors: []error{wantErr, wantErr, wantErr},
 		})
 	server.testSpanner.PutExecutionTime(testutil.MethodCommitTransaction,
 		testutil.SimulatedExecutionTime{
 			Errors: []error{wantErr, wantErr, wantErr},
 		})

 	txn := client.ReadOnlyTransaction()
 	defer txn.Close()

 	if _, _, got := txn.acquire(ctx); !testEqual(wantErr, got) {
 		t.Fatalf("Expect acquire to fail, got %v, want %v.", got, wantErr)
 	}

 	// The failure should recycle the session, we expect it to be used in
 	// following requests.
 	if got := txn.Query(ctx, NewStatement("SELECT 1")); !testEqual(wantErr, got.err) {
 		t.Fatalf("Expect Query to fail, got %v, want %v.", got.err, wantErr)
 	}

 	if got := txn.Read(ctx, "Users", KeySets(Key{"alice"}, Key{"bob"}), []string{"name", "email"}); !testEqual(wantErr, got.err) {
 		t.Fatalf("Expect Read to fail, got %v, want %v.", got.err, wantErr)
 	}

 	ms := []*Mutation{
 		Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(1), "Foo", int64(50)}),
 		Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(2), "Bar", int64(1)}),
 	}
 	if _, got := client.Apply(ctx, ms, ApplyAtLeastOnce()); !testEqual(wantErr, got) {
 		t.Fatalf("Expect Apply to fail, got %v, want %v.", got, wantErr)
 	}
 }

 // When an error is returned from the closure sent into ReadWriteTransaction, it
 // kicks off a rollback.
 func TestReadWriteTransaction_ErrorReturned(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 	server, client := newSpannerInMemTestServer(t)
 	defer server.teardown(client)

 	want := errors.New("an error")
 	_, got := client.ReadWriteTransaction(ctx, func(context.Context, *ReadWriteTransaction) error {
 		return want
 	})
 	if got != want {
 		t.Fatalf("got %+v, want %+v", got, want)
 	}
 	requests := drainRequestsFromServer(server.testSpanner)
 	if err := compareRequests([]interface{}{
 		&sppb.CreateSessionRequest{},
 		&sppb.BeginTransactionRequest{},
 		&sppb.RollbackRequest{}}, requests); err != nil {
 		// TODO: remove this once the session pool maintainer has been changed
 		// so that is doesn't delete sessions already during the first
 		// maintenance window.
 		// If we failed to get 3, it might have because - due to timing - we got
 		// a fourth request. If this request is DeleteSession, that's OK and
 		// expected.
 		if err := compareRequests([]interface{}{
 			&sppb.CreateSessionRequest{},
 			&sppb.BeginTransactionRequest{},
 			&sppb.RollbackRequest{},
 			&sppb.DeleteSessionRequest{}}, requests); err != nil {
 			t.Fatal(err)
 		}
 	}
 }

 func TestBatchDML_WithMultipleDML(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 	server, client := newSpannerInMemTestServer(t)
 	defer server.teardown(client)

 	_, err := client.ReadWriteTransaction(ctx, func(ctx context.Context, tx *ReadWriteTransaction) (err error) {
 		if _, err = tx.Update(ctx, Statement{SQL: updateBarSetFoo}); err != nil {
 			return err
 		}
 		if _, err = tx.BatchUpdate(ctx, []Statement{{SQL: updateBarSetFoo}, {SQL: updateBarSetFoo}}); err != nil {
 			return err
 		}
 		if _, err = tx.Update(ctx, Statement{SQL: updateBarSetFoo}); err != nil {
 			return err
 		}
 		_, err = tx.BatchUpdate(ctx, []Statement{{SQL: updateBarSetFoo}})
 		return err
 	})
 	if err != nil {
 		t.Fatal(err)
 	}

 	gotReqs, err := shouldHaveReceived(server.testSpanner, []interface{}{
 		&sppb.CreateSessionRequest{},
 		&sppb.BeginTransactionRequest{},
 		&sppb.ExecuteSqlRequest{},
 		&sppb.ExecuteBatchDmlRequest{},
 		&sppb.ExecuteSqlRequest{},
 		&sppb.ExecuteBatchDmlRequest{},
 		&sppb.CommitRequest{},
 	})
 	if err != nil {
 		t.Fatal(err)
 	}

 	if got, want := gotReqs[2].(*sppb.ExecuteSqlRequest).Seqno, int64(1); got != want {
 		t.Errorf("got %d, want %d", got, want)
 	}
 	if got, want := gotReqs[3].(*sppb.ExecuteBatchDmlRequest).Seqno, int64(2); got != want {
 		t.Errorf("got %d, want %d", got, want)
 	}
 	if got, want := gotReqs[4].(*sppb.ExecuteSqlRequest).Seqno, int64(3); got != want {
 		t.Errorf("got %d, want %d", got, want)
 	}
 	if got, want := gotReqs[5].(*sppb.ExecuteBatchDmlRequest).Seqno, int64(4); got != want {
 		t.Errorf("got %d, want %d", got, want)
 	}
 }

 // shouldHaveReceived asserts that exactly expectedRequests were present in
 // the server's ReceivedRequests channel. It only looks at type, not contents.
 //
 // Note: this in-place modifies serverClientMock by popping items off the
 // ReceivedRequests channel.
 func shouldHaveReceived(server testutil.InMemSpannerServer, want []interface{}) ([]interface{}, error) {
 	got := drainRequestsFromServer(server)
 	return got, compareRequests(want, got)
 }

 // Compares expected requests (want) with actual requests (got).
 func compareRequests(want []interface{}, got []interface{}) error {
 	if len(got) != len(want) {
 		var gotMsg string
 		for _, r := range got {
 			gotMsg += fmt.Sprintf("%v: %+v]\n", reflect.TypeOf(r), r)
 		}

 		var wantMsg string
 		for _, r := range want {
 			wantMsg += fmt.Sprintf("%v: %+v]\n", reflect.TypeOf(r), r)
 		}

 		return fmt.Errorf("got %d requests, want %d requests:\ngot:\n%s\nwant:\n%s", len(got), len(want), gotMsg, wantMsg)
 	}

 	for i, want := range want {
 		if reflect.TypeOf(got[i]) != reflect.TypeOf(want) {
 			return fmt.Errorf("request %d: got %+v, want %+v", i, reflect.TypeOf(got[i]), reflect.TypeOf(want))
 		}
 	}
 	return nil
 }

 func drainRequestsFromServer(server testutil.InMemSpannerServer) []interface{} {
 	var reqs []interface{}
 loop:
 	for {
 		select {
 		case req := <-server.ReceivedRequests():
 			reqs = append(reqs, req)
 		default:
 			break loop
 		}
 	}
 	return reqs
 }
	/*
	Copyright 2017 Google LLC

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	*/

	package spanner

	import (
	"context"
	"errors"
	"fmt"
	"reflect"
	"sync"
	"testing"
	"time"

	"cloud.google.com/go/spanner/internal/testutil"
	sppb "google.golang.org/genproto/googleapis/spanner/v1"
	"google.golang.org/grpc/codes"
	gstatus "google.golang.org/grpc/status"
	)

	// Single can only be used once.
	func TestSingle(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	server, client := newSpannerInMemTestServer(t)
	defer server.teardown(client)

	txn := client.Single()
	defer txn.Close()
	_, _, e := txn.acquire(ctx)
	if e != nil {
	t.Fatalf("Acquire for single use, got %v, want nil.", e)
	}
	_, _, e = txn.acquire(ctx)
	if wantErr := errTxClosed(); !testEqual(e, wantErr) {
	t.Fatalf("Second acquire for single use, got %v, want %v.", e, wantErr)
	}

	// Only one CreateSessionRequest is sent.
	if _, err := shouldHaveReceived(server.testSpanner, []interface{}{&sppb.CreateSessionRequest{}}); err != nil {
	t.Fatal(err)
	}
	}

	// Re-using ReadOnlyTransaction: can recover from acquire failure.
	func TestReadOnlyTransaction_RecoverFromFailure(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	server, client := newSpannerInMemTestServer(t)
	defer server.teardown(client)

	txn := client.ReadOnlyTransaction()
	defer txn.Close()

	// First request will fail.
	errUsr := gstatus.Error(codes.Unknown, "error")
	server.testSpanner.PutExecutionTime(testutil.MethodBeginTransaction,
	testutil.SimulatedExecutionTime{
	Errors: []error{errUsr},
	})

	_, _, e := txn.acquire(ctx)
	if wantErr := toSpannerError(errUsr); !testEqual(e, wantErr) {
	t.Fatalf("Acquire for multi use, got %v, want %v.", e, wantErr)
	}
	_, _, e = txn.acquire(ctx)
	if e != nil {
	t.Fatalf("Acquire for multi use, got %v, want nil.", e)
	}
	}

	// ReadOnlyTransaction: can not be used after close.
	func TestReadOnlyTransaction_UseAfterClose(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	server, client := newSpannerInMemTestServer(t)
	defer server.teardown(client)

	txn := client.ReadOnlyTransaction()
	txn.Close()

	_, _, e := txn.acquire(ctx)
	if wantErr := errTxClosed(); !testEqual(e, wantErr) {
	t.Fatalf("Second acquire for multi use, got %v, want %v.", e, wantErr)
	}
	}

	// ReadOnlyTransaction: can be acquired concurrently.
	func TestReadOnlyTransaction_Concurrent(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	server, client := newSpannerInMemTestServer(t)
	defer server.teardown(client)
	txn := client.ReadOnlyTransaction()
	defer txn.Close()

	server.testSpanner.Freeze()
	var (
	sh1 *sessionHandle
	sh2 *sessionHandle
	ts1 *sppb.TransactionSelector
	ts2 *sppb.TransactionSelector
	wg = sync.WaitGroup{}
	)
	acquire := func(sh sessionHandle, ts sppb.TransactionSelector) {
	defer wg.Done()
	var e error
	sh, ts, e = txn.acquire(ctx)
	if e != nil {
	t.Errorf("Concurrent acquire for multiuse, got %v, expect nil.", e)
	}
	}
	wg.Add(2)
	go acquire(&sh1, &ts1)
	go acquire(&sh2, &ts2)

	// TODO(deklerk): Get rid of this.
	<-time.After(100 * time.Millisecond)

	server.testSpanner.Unfreeze()
	wg.Wait()
	if sh1.session.id != sh2.session.id {
	t.Fatalf("Expected acquire to get same session handle, got %v and %v.", sh1, sh2)
	}
	if !testEqual(ts1, ts2) {
	t.Fatalf("Expected acquire to get same transaction selector, got %v and %v.", ts1, ts2)
	}
	}

	func TestApply_Single(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	server, client := newSpannerInMemTestServer(t)
	defer server.teardown(client)

	ms := []*Mutation{
	Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(1), "Foo", int64(50)}),
	Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(2), "Bar", int64(1)}),
	}
	if _, e := client.Apply(ctx, ms, ApplyAtLeastOnce()); e != nil {
	t.Fatalf("applyAtLeastOnce retry on abort, got %v, want nil.", e)
	}

	if _, err := shouldHaveReceived(server.testSpanner, []interface{}{
	&sppb.CreateSessionRequest{},
	&sppb.CommitRequest{},
	}); err != nil {
	t.Fatal(err)
	}
	}

	// Transaction retries on abort.
	func TestApply_RetryOnAbort(t *testing.T) {
	ctx := context.Background()
	t.Parallel()
	server, client := newSpannerInMemTestServer(t)
	defer server.teardown(client)

	// First commit will fail, and the retry will begin a new transaction.
	errAbrt := spannerErrorf(codes.Aborted, "")
	server.testSpanner.PutExecutionTime(testutil.MethodCommitTransaction,
	testutil.SimulatedExecutionTime{
	Errors: []error{errAbrt},
	})

	ms := []*Mutation{
	Insert("Accounts", []string{"AccountId"}, []interface{}{int64(1)}),
	}

	if _, e := client.Apply(ctx, ms); e != nil {
	t.Fatalf("ReadWriteTransaction retry on abort, got %v, want nil.", e)
	}

	if _, err := shouldHaveReceived(server.testSpanner, []interface{}{
	&sppb.CreateSessionRequest{},
	&sppb.BeginTransactionRequest{},
	&sppb.CommitRequest{}, // First commit fails.
	&sppb.BeginTransactionRequest{},
	&sppb.CommitRequest{}, // Second commit succeeds.
	}); err != nil {
	t.Fatal(err)
	}
	}

	// Tests that NotFound errors cause failures, and aren't retried.
	func TestTransaction_NotFound(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	server, client := newSpannerInMemTestServer(t)
	defer server.teardown(client)

	wantErr := spannerErrorf(codes.NotFound, "Session not found")
	server.testSpanner.PutExecutionTime(testutil.MethodBeginTransaction,
	testutil.SimulatedExecutionTime{
	Errors: []error{wantErr, wantErr, wantErr},
	})
	server.testSpanner.PutExecutionTime(testutil.MethodCommitTransaction,
	testutil.SimulatedExecutionTime{
	Errors: []error{wantErr, wantErr, wantErr},
	})

	txn := client.ReadOnlyTransaction()
	defer txn.Close()

	if _, _, got := txn.acquire(ctx); !testEqual(wantErr, got) {
	t.Fatalf("Expect acquire to fail, got %v, want %v.", got, wantErr)
	}

	// The failure should recycle the session, we expect it to be used in
	// following requests.
	if got := txn.Query(ctx, NewStatement("SELECT 1")); !testEqual(wantErr, got.err) {
	t.Fatalf("Expect Query to fail, got %v, want %v.", got.err, wantErr)
	}

	if got := txn.Read(ctx, "Users", KeySets(Key{"alice"}, Key{"bob"}), []string{"name", "email"}); !testEqual(wantErr, got.err) {
	t.Fatalf("Expect Read to fail, got %v, want %v.", got.err, wantErr)
	}

	ms := []*Mutation{
	Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(1), "Foo", int64(50)}),
	Insert("Accounts", []string{"AccountId", "Nickname", "Balance"}, []interface{}{int64(2), "Bar", int64(1)}),
	}
	if _, got := client.Apply(ctx, ms, ApplyAtLeastOnce()); !testEqual(wantErr, got) {
	t.Fatalf("Expect Apply to fail, got %v, want %v.", got, wantErr)
	}
	}

	// When an error is returned from the closure sent into ReadWriteTransaction, it
	// kicks off a rollback.
	func TestReadWriteTransaction_ErrorReturned(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	server, client := newSpannerInMemTestServer(t)
	defer server.teardown(client)

	want := errors.New("an error")
	_, got := client.ReadWriteTransaction(ctx, func(context.Context, *ReadWriteTransaction) error {
	return want
	})
	if got != want {
	t.Fatalf("got %+v, want %+v", got, want)
	}
	requests := drainRequestsFromServer(server.testSpanner)
	if err := compareRequests([]interface{}{
	&sppb.CreateSessionRequest{},
	&sppb.BeginTransactionRequest{},
	&sppb.RollbackRequest{}}, requests); err != nil {
	// TODO: remove this once the session pool maintainer has been changed
	// so that is doesn't delete sessions already during the first
	// maintenance window.
	// If we failed to get 3, it might have because - due to timing - we got
	// a fourth request. If this request is DeleteSession, that's OK and
	// expected.
	if err := compareRequests([]interface{}{
	&sppb.CreateSessionRequest{},
	&sppb.BeginTransactionRequest{},
	&sppb.RollbackRequest{},
	&sppb.DeleteSessionRequest{}}, requests); err != nil {
	t.Fatal(err)
	}
	}
	}

	func TestBatchDML_WithMultipleDML(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	server, client := newSpannerInMemTestServer(t)
	defer server.teardown(client)

	_, err := client.ReadWriteTransaction(ctx, func(ctx context.Context, tx *ReadWriteTransaction) (err error) {
	if _, err = tx.Update(ctx, Statement{SQL: updateBarSetFoo}); err != nil {
	return err
	}
	if _, err = tx.BatchUpdate(ctx, []Statement{{SQL: updateBarSetFoo}, {SQL: updateBarSetFoo}}); err != nil {
	return err
	}
	if _, err = tx.Update(ctx, Statement{SQL: updateBarSetFoo}); err != nil {
	return err
	}
	_, err = tx.BatchUpdate(ctx, []Statement{{SQL: updateBarSetFoo}})
	return err
	})
	if err != nil {
	t.Fatal(err)
	}

	gotReqs, err := shouldHaveReceived(server.testSpanner, []interface{}{
	&sppb.CreateSessionRequest{},
	&sppb.BeginTransactionRequest{},
	&sppb.ExecuteSqlRequest{},
	&sppb.ExecuteBatchDmlRequest{},
	&sppb.ExecuteSqlRequest{},
	&sppb.ExecuteBatchDmlRequest{},
	&sppb.CommitRequest{},
	})
	if err != nil {
	t.Fatal(err)
	}

	if got, want := gotReqs[2].(*sppb.ExecuteSqlRequest).Seqno, int64(1); got != want {
	t.Errorf("got %d, want %d", got, want)
	}
	if got, want := gotReqs[3].(*sppb.ExecuteBatchDmlRequest).Seqno, int64(2); got != want {
	t.Errorf("got %d, want %d", got, want)
	}
	if got, want := gotReqs[4].(*sppb.ExecuteSqlRequest).Seqno, int64(3); got != want {
	t.Errorf("got %d, want %d", got, want)
	}
	if got, want := gotReqs[5].(*sppb.ExecuteBatchDmlRequest).Seqno, int64(4); got != want {
	t.Errorf("got %d, want %d", got, want)
	}
	}

	// shouldHaveReceived asserts that exactly expectedRequests were present in
	// the server's ReceivedRequests channel. It only looks at type, not contents.
	//
	// Note: this in-place modifies serverClientMock by popping items off the
	// ReceivedRequests channel.
	func shouldHaveReceived(server testutil.InMemSpannerServer, want []interface{}) ([]interface{}, error) {
	got := drainRequestsFromServer(server)
	return got, compareRequests(want, got)
	}

	// Compares expected requests (want) with actual requests (got).
	func compareRequests(want []interface{}, got []interface{}) error {
	if len(got) != len(want) {
	var gotMsg string
	for _, r := range got {
	gotMsg += fmt.Sprintf("%v: %+v]\n", reflect.TypeOf(r), r)
	}

	var wantMsg string
	for _, r := range want {
	wantMsg += fmt.Sprintf("%v: %+v]\n", reflect.TypeOf(r), r)
	}

	return fmt.Errorf("got %d requests, want %d requests:\ngot:\n%s\nwant:\n%s", len(got), len(want), gotMsg, wantMsg)
	}

	for i, want := range want {
	if reflect.TypeOf(got[i]) != reflect.TypeOf(want) {
	return fmt.Errorf("request %d: got %+v, want %+v", i, reflect.TypeOf(got[i]), reflect.TypeOf(want))
	}
	}
	return nil
	}

	func drainRequestsFromServer(server testutil.InMemSpannerServer) []interface{} {
	var reqs []interface{}
	loop:
	for {
	select {
	case req := <-server.ReceivedRequests():
	reqs = append(reqs, req)
	default:
	break loop
	}
	}
	return reqs
	}