Golang roachpb.MakeValueFromBytes函数代码示例

func runMVCCConditionalPut(emk engineMaker, valueSize int, createFirst bool, b *testing.B) {
	rng, _ := randutil.NewPseudoRand()
	value := roachpb.MakeValueFromBytes(randutil.RandBytes(rng, valueSize))
	keyBuf := append(make([]byte, 0, 64), []byte("key-")...)

	eng := emk(b, fmt.Sprintf("cput_%d", valueSize))
	defer eng.Close()

	b.SetBytes(int64(valueSize))
	var expected *roachpb.Value
	if createFirst {
		for i := 0; i < b.N; i++ {
			key := roachpb.Key(encoding.EncodeUvarintAscending(keyBuf[:4], uint64(i)))
			ts := makeTS(timeutil.Now().UnixNano(), 0)
			if err := MVCCPut(context.Background(), eng, nil, key, ts, value, nil); err != nil {
				b.Fatalf("failed put: %s", err)
			}
		}
		expected = &value
	}

	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		key := roachpb.Key(encoding.EncodeUvarintAscending(keyBuf[:4], uint64(i)))
		ts := makeTS(timeutil.Now().UnixNano(), 0)
		if err := MVCCConditionalPut(context.Background(), eng, nil, key, ts, value, expected, nil); err != nil {
			b.Fatalf("failed put: %s", err)
		}
	}

	b.StopTimer()
}

func BenchmarkMVCCPutDelete_RocksDB(b *testing.B) {
	rocksdb := setupMVCCInMemRocksDB(b, "put_delete")
	defer rocksdb.Close()

	r := rand.New(rand.NewSource(int64(timeutil.Now().UnixNano())))
	value := roachpb.MakeValueFromBytes(randutil.RandBytes(r, 10))
	zeroTS := hlc.ZeroTimestamp
	var blockNum int64

	for i := 0; i < b.N; i++ {
		blockID := r.Int63()
		blockNum++
		key := encoding.EncodeVarintAscending(nil, blockID)
		key = encoding.EncodeVarintAscending(key, blockNum)

		if err := MVCCPut(context.Background(), rocksdb, nil, key, zeroTS, value, nil /* txn */); err != nil {
			b.Fatal(err)
		}
		if err := MVCCDelete(context.Background(), rocksdb, nil, key, zeroTS, nil /* txn */); err != nil {
			b.Fatal(err)
		}
	}
}

func runMVCCBatchPut(emk engineMaker, valueSize, batchSize int, b *testing.B) {
	rng, _ := randutil.NewPseudoRand()
	value := roachpb.MakeValueFromBytes(randutil.RandBytes(rng, valueSize))
	keyBuf := append(make([]byte, 0, 64), []byte("key-")...)

	eng := emk(b, fmt.Sprintf("batch_put_%d_%d", valueSize, batchSize))
	defer eng.Close()

	b.SetBytes(int64(valueSize))
	b.ResetTimer()

	for i := 0; i < b.N; i += batchSize {
		end := i + batchSize
		if end > b.N {
			end = b.N
		}

		batch := eng.NewBatch()

		for j := i; j < end; j++ {
			key := roachpb.Key(encoding.EncodeUvarintAscending(keyBuf[:4], uint64(j)))
			ts := makeTS(timeutil.Now().UnixNano(), 0)
			if err := MVCCPut(context.Background(), batch, nil, key, ts, value, nil); err != nil {
				b.Fatalf("failed put: %s", err)
			}
		}

		if err := batch.Commit(); err != nil {
			b.Fatal(err)
		}

		batch.Close()
	}

	b.StopTimer()
}

// setupMVCCData writes up to numVersions values at each of numKeys
// keys. The number of versions written for each key is chosen
// randomly according to a uniform distribution. Each successive
// version is written starting at 5ns and then in 5ns increments. This
// allows scans at various times, starting at t=5ns, and continuing to
// t=5ns*(numVersions+1). A version for each key will be read on every
// such scan, but the dynamics of the scan will change depending on
// the historical timestamp. Earlier timestamps mean scans which must
// skip more historical versions; later timestamps mean scans which
// skip fewer.
//
// The creation of the database is time consuming, especially for larger
// numbers of versions. The database is persisted between runs and stored in
// the current directory as "mvcc_scan_<versions>_<keys>_<valueBytes>" (which
// is also returned).
func setupMVCCData(
	emk engineMaker, numVersions, numKeys, valueBytes int, b *testing.B,
) (Engine, string) {
	loc := fmt.Sprintf("mvcc_data_%d_%d_%d", numVersions, numKeys, valueBytes)

	exists := true
	if _, err := os.Stat(loc); os.IsNotExist(err) {
		exists = false
	}

	eng := emk(b, loc)

	if exists {
		readAllFiles(filepath.Join(loc, "*"))
		return eng, loc
	}

	log.Infof(context.Background(), "creating mvcc data: %s", loc)

	// Generate the same data every time.
	rng := rand.New(rand.NewSource(1449168817))

	keys := make([]roachpb.Key, numKeys)
	var order []int
	for i := 0; i < numKeys; i++ {
		keys[i] = roachpb.Key(encoding.EncodeUvarintAscending([]byte("key-"), uint64(i)))
		keyVersions := rng.Intn(numVersions) + 1
		for j := 0; j < keyVersions; j++ {
			order = append(order, i)
		}
	}

	// Randomize the order in which the keys are written.
	for i, n := 0, len(order); i < n-1; i++ {
		j := i + rng.Intn(n-i)
		order[i], order[j] = order[j], order[i]
	}

	counts := make([]int, numKeys)
	batch := eng.NewBatch()
	for i, idx := range order {
		// Output the keys in ~20 batches. If we used a single batch to output all
		// of the keys rocksdb would create a single sstable. We want multiple
		// sstables in order to exercise filtering of which sstables are examined
		// during iterator seeking. We fix the number of batches we output so that
		// optimizations which change the data size result in the same number of
		// sstables.
		if scaled := len(order) / 20; i > 0 && (i%scaled) == 0 {
			log.Infof(context.Background(), "committing (%d/~%d)", i/scaled, 20)
			if err := batch.Commit(); err != nil {
				b.Fatal(err)
			}
			batch.Close()
			batch = eng.NewBatch()
			if err := eng.Flush(); err != nil {
				b.Fatal(err)
			}
		}

		key := keys[idx]
		ts := makeTS(int64(counts[idx]+1)*5, 0)
		counts[idx]++
		value := roachpb.MakeValueFromBytes(randutil.RandBytes(rng, valueBytes))
		value.InitChecksum(key)
		if err := MVCCPut(context.Background(), batch, nil, key, ts, value, nil); err != nil {
			b.Fatal(err)
		}
	}
	if err := batch.Commit(); err != nil {
		b.Fatal(err)
	}
	batch.Close()
	if err := eng.Flush(); err != nil {
		b.Fatal(err)
	}

	return eng, loc
}

// TestMultiRangeScanWithMaxResults tests that commands which access multiple
// ranges with MaxResults parameter are carried out properly.
func TestMultiRangeScanWithMaxResults(t *testing.T) {
	defer leaktest.AfterTest(t)()
	testCases := []struct {
		splitKeys []roachpb.Key
		keys      []roachpb.Key
	}{
		{[]roachpb.Key{roachpb.Key("m")},
			[]roachpb.Key{roachpb.Key("a"), roachpb.Key("z")}},
		{[]roachpb.Key{roachpb.Key("h"), roachpb.Key("q")},
			[]roachpb.Key{roachpb.Key("b"), roachpb.Key("f"), roachpb.Key("k"),
				roachpb.Key("r"), roachpb.Key("w"), roachpb.Key("y")}},
	}

	for i, tc := range testCases {
		s, _, _ := serverutils.StartServer(t, base.TestServerArgs{})
		defer s.Stopper().Stop()
		ts := s.(*TestServer)
		retryOpts := base.DefaultRetryOptions()
		retryOpts.Closer = ts.stopper.ShouldQuiesce()
		ds := kv.NewDistSender(kv.DistSenderConfig{
			Clock:           s.Clock(),
			RPCContext:      s.RPCContext(),
			RPCRetryOptions: &retryOpts,
		}, ts.Gossip())
		ambient := log.AmbientContext{Tracer: tracing.NewTracer()}
		tds := kv.NewTxnCoordSender(
			ambient,
			ds,
			ts.Clock(),
			ts.Cfg.Linearizable,
			ts.stopper,
			kv.MakeTxnMetrics(metric.TestSampleInterval),
		)

		for _, sk := range tc.splitKeys {
			if err := ts.node.storeCfg.DB.AdminSplit(context.TODO(), sk); err != nil {
				t.Fatal(err)
			}
		}

		for _, k := range tc.keys {
			put := roachpb.NewPut(k, roachpb.MakeValueFromBytes(k))
			if _, err := client.SendWrapped(context.Background(), tds, put); err != nil {
				t.Fatal(err)
			}
		}

		// Try every possible ScanRequest startKey.
		for start := 0; start < len(tc.keys); start++ {
			// Try every possible maxResults, from 1 to beyond the size of key array.
			for maxResults := 1; maxResults <= len(tc.keys)-start+1; maxResults++ {
				scan := roachpb.NewScan(tc.keys[start], tc.keys[len(tc.keys)-1].Next())
				reply, err := client.SendWrappedWith(
					context.Background(), tds, roachpb.Header{MaxSpanRequestKeys: int64(maxResults)}, scan,
				)
				if err != nil {
					t.Fatal(err)
				}
				rows := reply.(*roachpb.ScanResponse).Rows
				if start+maxResults <= len(tc.keys) && len(rows) != maxResults {
					t.Errorf("%d: start=%s: expected %d rows, but got %d", i, tc.keys[start], maxResults, len(rows))
				} else if start+maxResults == len(tc.keys)+1 && len(rows) != maxResults-1 {
					t.Errorf("%d: expected %d rows, but got %d", i, maxResults-1, len(rows))
				}
			}
		}
	}
}

// TestMultiRangeScanDeleteRange tests that commands which access multiple
// ranges are carried out properly.
func TestMultiRangeScanDeleteRange(t *testing.T) {
	defer leaktest.AfterTest(t)()
	s, _, _ := serverutils.StartServer(t, base.TestServerArgs{})
	defer s.Stopper().Stop()
	ts := s.(*TestServer)
	retryOpts := base.DefaultRetryOptions()
	retryOpts.Closer = ts.stopper.ShouldQuiesce()
	ds := kv.NewDistSender(kv.DistSenderConfig{
		Clock:           s.Clock(),
		RPCContext:      s.RPCContext(),
		RPCRetryOptions: &retryOpts,
	}, ts.Gossip())
	ambient := log.AmbientContext{Tracer: tracing.NewTracer()}
	tds := kv.NewTxnCoordSender(
		ambient,
		ds,
		s.Clock(),
		ts.Cfg.Linearizable,
		ts.stopper,
		kv.MakeTxnMetrics(metric.TestSampleInterval),
	)

	if err := ts.node.storeCfg.DB.AdminSplit(context.TODO(), "m"); err != nil {
		t.Fatal(err)
	}
	writes := []roachpb.Key{roachpb.Key("a"), roachpb.Key("z")}
	get := &roachpb.GetRequest{
		Span: roachpb.Span{Key: writes[0]},
	}
	get.EndKey = writes[len(writes)-1]
	if _, err := client.SendWrapped(context.Background(), tds, get); err == nil {
		t.Errorf("able to call Get with a key range: %v", get)
	}
	var delTS hlc.Timestamp
	for i, k := range writes {
		put := roachpb.NewPut(k, roachpb.MakeValueFromBytes(k))
		if _, err := client.SendWrapped(context.Background(), tds, put); err != nil {
			t.Fatal(err)
		}
		scan := roachpb.NewScan(writes[0], writes[len(writes)-1].Next())
		reply, err := client.SendWrapped(context.Background(), tds, scan)
		if err != nil {
			t.Fatal(err)
		}
		sr := reply.(*roachpb.ScanResponse)
		if sr.Txn != nil {
			// This was the other way around at some point in the past.
			// Same below for Delete, etc.
			t.Errorf("expected no transaction in response header")
		}
		if rows := sr.Rows; len(rows) != i+1 {
			t.Fatalf("expected %d rows, but got %d", i+1, len(rows))
		}
	}

	del := &roachpb.DeleteRangeRequest{
		Span: roachpb.Span{
			Key:    writes[0],
			EndKey: roachpb.Key(writes[len(writes)-1]).Next(),
		},
		ReturnKeys: true,
	}
	reply, err := client.SendWrappedWith(context.Background(), tds, roachpb.Header{Timestamp: delTS}, del)
	if err != nil {
		t.Fatal(err)
	}
	dr := reply.(*roachpb.DeleteRangeResponse)
	if dr.Txn != nil {
		t.Errorf("expected no transaction in response header")
	}
	if !reflect.DeepEqual(dr.Keys, writes) {
		t.Errorf("expected %d keys to be deleted, but got %d instead", writes, dr.Keys)
	}

	scan := roachpb.NewScan(writes[0], writes[len(writes)-1].Next())
	txn := &roachpb.Transaction{Name: "MyTxn"}
	reply, err = client.SendWrappedWith(context.Background(), tds, roachpb.Header{Txn: txn}, scan)
	if err != nil {
		t.Fatal(err)
	}
	sr := reply.(*roachpb.ScanResponse)
	if txn := sr.Txn; txn == nil || txn.Name != "MyTxn" {
		t.Errorf("wanted Txn to persist, but it changed to %v", txn)
	}
	if rows := sr.Rows; len(rows) > 0 {
		t.Fatalf("scan after delete returned rows: %v", rows)
	}
}

// TestKVDBCoverage verifies that all methods may be invoked on the
// key value database.
func TestKVDBCoverage(t *testing.T) {
	defer leaktest.AfterTest(t)()
	s, _, _ := serverutils.StartServer(t, base.TestServerArgs{})
	defer s.Stopper().Stop()
	ctx := context.TODO()

	db := createTestClient(t, s)
	key := roachpb.Key("a")
	value1 := []byte("value1")
	value2 := []byte("value2")
	value3 := []byte("value3")

	// Put first value at key.
	if pErr := db.Put(context.TODO(), key, value1); pErr != nil {
		t.Fatal(pErr)
	}

	// Verify put.
	if gr, pErr := db.Get(ctx, key); pErr != nil {
		t.Fatal(pErr)
	} else if !gr.Exists() {
		t.Error("expected key to exist")
	}

	// Conditional put should succeed, changing value1 to value2.
	if pErr := db.CPut(context.TODO(), key, value2, value1); pErr != nil {
		t.Fatal(pErr)
	}

	// Verify get by looking up conditional put value.
	if gr, pErr := db.Get(ctx, key); pErr != nil {
		t.Fatal(pErr)
	} else if !bytes.Equal(gr.ValueBytes(), value2) {
		t.Errorf("expected get to return %q; got %q", value2, gr.ValueBytes())
	}

	// Increment.
	if ir, pErr := db.Inc(ctx, "i", 10); pErr != nil {
		t.Fatal(pErr)
	} else if ir.ValueInt() != 10 {
		t.Errorf("expected increment new value of %d; got %d", 10, ir.ValueInt())
	}

	// Delete conditional put value.
	if pErr := db.Del(ctx, key); pErr != nil {
		t.Fatal(pErr)
	}
	if gr, pErr := db.Get(ctx, key); pErr != nil {
		t.Fatal(pErr)
	} else if gr.Exists() {
		t.Error("expected key to not exist after delete")
	}

	// Put values in anticipation of scan & delete range.
	keyValues := []roachpb.KeyValue{
		{Key: roachpb.Key("a"), Value: roachpb.MakeValueFromBytes(value1)},
		{Key: roachpb.Key("b"), Value: roachpb.MakeValueFromBytes(value2)},
		{Key: roachpb.Key("c"), Value: roachpb.MakeValueFromBytes(value3)},
	}
	for _, kv := range keyValues {
		valueBytes, pErr := kv.Value.GetBytes()
		if pErr != nil {
			t.Fatal(pErr)
		}
		if pErr := db.Put(context.TODO(), kv.Key, valueBytes); pErr != nil {
			t.Fatal(pErr)
		}
	}
	if rows, pErr := db.Scan(context.TODO(), "a", "d", 0); pErr != nil {
		t.Fatal(pErr)
	} else if len(rows) != len(keyValues) {
		t.Fatalf("expected %d rows in scan; got %d", len(keyValues), len(rows))
	} else {
		for i, kv := range keyValues {
			valueBytes, pErr := kv.Value.GetBytes()
			if pErr != nil {
				t.Fatal(pErr)
			}
			if !bytes.Equal(rows[i].ValueBytes(), valueBytes) {
				t.Errorf("%d: key %q, values %q != %q", i, kv.Key, rows[i].ValueBytes(), valueBytes)
			}
		}
	}

	// Test reverse scan.
	if rows, pErr := db.ReverseScan(context.TODO(), "a", "d", 0); pErr != nil {
		t.Fatal(pErr)
	} else if len(rows) != len(keyValues) {
		t.Fatalf("expected %d rows in scan; got %d", len(keyValues), len(rows))
	} else {
		for i, kv := range keyValues {
			valueBytes, pErr := kv.Value.GetBytes()
			if pErr != nil {
				t.Fatal(pErr)
			}
			if !bytes.Equal(rows[len(keyValues)-1-i].ValueBytes(), valueBytes) {
				t.Errorf("%d: key %q, values %q != %q", i, kv.Key, rows[len(keyValues)-i].ValueBytes(), valueBytes)
			}
//.........这里部分代码省略.........

func TestIndexKey(t *testing.T) {
	rng, _ := randutil.NewPseudoRand()
	var a DatumAlloc

	tests := []indexKeyTest{
		{nil, nil,
			[]parser.Datum{parser.NewDInt(10)},
			[]parser.Datum{parser.NewDInt(20)},
		},
		{[]ID{100}, nil,
			[]parser.Datum{parser.NewDInt(10), parser.NewDInt(11)},
			[]parser.Datum{parser.NewDInt(20)},
		},
		{[]ID{100, 200}, nil,
			[]parser.Datum{parser.NewDInt(10), parser.NewDInt(11), parser.NewDInt(12)},
			[]parser.Datum{parser.NewDInt(20)},
		},
		{nil, []ID{100},
			[]parser.Datum{parser.NewDInt(10)},
			[]parser.Datum{parser.NewDInt(20), parser.NewDInt(21)},
		},
		{[]ID{100}, []ID{100},
			[]parser.Datum{parser.NewDInt(10), parser.NewDInt(11)},
			[]parser.Datum{parser.NewDInt(20), parser.NewDInt(21)},
		},
		{[]ID{100}, []ID{200},
			[]parser.Datum{parser.NewDInt(10), parser.NewDInt(11)},
			[]parser.Datum{parser.NewDInt(20), parser.NewDInt(21)},
		},
		{[]ID{100, 200}, []ID{100, 300},
			[]parser.Datum{parser.NewDInt(10), parser.NewDInt(11), parser.NewDInt(12)},
			[]parser.Datum{parser.NewDInt(20), parser.NewDInt(21), parser.NewDInt(22)},
		},
	}

	for i := 0; i < 1000; i++ {
		var t indexKeyTest

		t.primaryInterleaves = make([]ID, rng.Intn(10))
		for j := range t.primaryInterleaves {
			t.primaryInterleaves[j] = ID(1 + rng.Intn(10))
		}
		valuesLen := randutil.RandIntInRange(rng, len(t.primaryInterleaves)+1, len(t.primaryInterleaves)+10)
		t.primaryValues = make([]parser.Datum, valuesLen)
		for j := range t.primaryValues {
			t.primaryValues[j] = RandDatum(rng, ColumnType{Kind: ColumnType_INT}, true)
		}

		t.secondaryInterleaves = make([]ID, rng.Intn(10))
		for j := range t.secondaryInterleaves {
			t.secondaryInterleaves[j] = ID(1 + rng.Intn(10))
		}
		valuesLen = randutil.RandIntInRange(rng, len(t.secondaryInterleaves)+1, len(t.secondaryInterleaves)+10)
		t.secondaryValues = make([]parser.Datum, valuesLen)
		for j := range t.secondaryValues {
			t.secondaryValues[j] = RandDatum(rng, ColumnType{Kind: ColumnType_INT}, true)
		}

		tests = append(tests, t)
	}

	for i, test := range tests {
		tableDesc, colMap := makeTableDescForTest(test)
		testValues := append(test.primaryValues, test.secondaryValues...)

		primaryKeyPrefix := MakeIndexKeyPrefix(&tableDesc, tableDesc.PrimaryIndex.ID)
		primaryKey, _, err := EncodeIndexKey(
			&tableDesc, &tableDesc.PrimaryIndex, colMap, testValues, primaryKeyPrefix)
		if err != nil {
			t.Fatal(err)
		}
		primaryValue := roachpb.MakeValueFromBytes(nil)
		primaryIndexKV := client.KeyValue{Key: primaryKey, Value: &primaryValue}

		secondaryIndexEntry, err := EncodeSecondaryIndex(
			&tableDesc, &tableDesc.Indexes[0], colMap, testValues)
		if err != nil {
			t.Fatal(err)
		}
		secondaryIndexKV := client.KeyValue{
			Key:   secondaryIndexEntry.Key,
			Value: &secondaryIndexEntry.Value,
		}

		checkEntry := func(index *IndexDescriptor, entry client.KeyValue) {
			values, err := decodeIndex(&a, &tableDesc, index, entry.Key)
			if err != nil {
				t.Fatal(err)
			}

			for j, value := range values {
				testValue := testValues[colMap[index.ColumnIDs[j]]]
				if value.Compare(testValue) != 0 {
					t.Fatalf("%d: value %d got %q but expected %q", i, j, value, testValue)
				}
			}

			indexID, _, err := DecodeIndexKeyPrefix(&a, &tableDesc, entry.Key)
			if err != nil {
				t.Fatal(err)
//.........这里部分代码省略.........

// This test checks backward compatibility with old data that contains
// sentinel k:v pairs at the start of each table row. Cockroachdb used
// to write table rows with sentinel values in the past. When a new column
// is added to such a table with the new column included in the same
// column family as the primary key columns, the sentinel k:v pairs
// start representing this new column. This test checks that the sentinel
// values represent NULL column values, and that an UPDATE to such
// a column works correctly.
func TestParseSentinelValueWithNewColumnInSentinelFamily(t *testing.T) {
	defer leaktest.AfterTest(t)()
	params, _ := createTestServerParams()
	server, sqlDB, kvDB := serverutils.StartServer(t, params)
	defer server.Stopper().Stop()

	if _, err := sqlDB.Exec(`
CREATE DATABASE t;
CREATE TABLE t.test (
	k INT PRIMARY KEY,
	FAMILY F1 (k)
);
`); err != nil {
		t.Fatal(err)
	}
	tableDesc := sqlbase.GetTableDescriptor(kvDB, "t", "test")
	if tableDesc.Families[0].DefaultColumnID != 0 {
		t.Fatalf("default column id not set properly: %s", tableDesc)
	}

	// Add some data.
	const maxValue = 10
	inserts := make([]string, maxValue+1)
	for i := range inserts {
		inserts[i] = fmt.Sprintf(`(%d)`, i)
	}
	if _, err := sqlDB.Exec(`INSERT INTO t.test VALUES ` + strings.Join(inserts, ",")); err != nil {
		t.Fatal(err)
	}

	// Convert table data created by the above INSERT into sentinel
	// values. This is done to make the table appear like it were
	// written in the past when cockroachdb used to write sentinel
	// values for each table row.
	startKey := roachpb.Key(keys.MakeTablePrefix(uint32(tableDesc.ID)))
	kvs, err := kvDB.Scan(
		context.TODO(),
		startKey,
		startKey.PrefixEnd(),
		maxValue+1)
	if err != nil {
		t.Fatal(err)
	}
	for _, kv := range kvs {
		value := roachpb.MakeValueFromBytes(nil)
		if err := kvDB.Put(context.TODO(), kv.Key, &value); err != nil {
			t.Fatal(err)
		}
	}

	// Add a new column that gets added to column family 0,
	// updating DefaultColumnID.
	if _, err := sqlDB.Exec(`ALTER TABLE t.test ADD COLUMN v INT FAMILY F1`); err != nil {
		t.Fatal(err)
	}
	tableDesc = sqlbase.GetTableDescriptor(kvDB, "t", "test")
	if tableDesc.Families[0].DefaultColumnID != 2 {
		t.Fatalf("default column id not set properly: %s", tableDesc)
	}

	// Update one of the rows.
	const setKey = 5
	const setVal = maxValue - setKey
	if _, err := sqlDB.Exec(`UPDATE t.test SET v = $1 WHERE k = $2`, setVal, setKey); err != nil {
		t.Fatal(err)
	}

	// The table contains the one updated value and remaining NULL values.
	rows, err := sqlDB.Query(`SELECT v from t.test`)
	if err != nil {
		t.Fatal(err)
	}
	const eCount = maxValue + 1
	count := 0
	for ; rows.Next(); count++ {
		var val *int
		if err := rows.Scan(&val); err != nil {
			t.Errorf("row %d scan failed: %s", count, err)
			continue
		}
		if count == setKey {
			if val != nil {
				if setVal != *val {
					t.Errorf("value = %d, expected %d", *val, setVal)
				}
			} else {
				t.Error("received nil value for column 'v'")
			}
		} else if val != nil {
			t.Error("received non NULL value for column 'v'")
		}
	}
//.........这里部分代码省略.........

// TestUncertaintyObservedTimestampForwarding checks that when receiving an
// uncertainty restart on a node, the next attempt to read (at the increased
// timestamp) is free from uncertainty. See roachpb.Transaction for details.
func TestUncertaintyMaxTimestampForwarding(t *testing.T) {
	defer leaktest.AfterTest(t)()

	dbCtx := client.DefaultDBContext()
	s := &localtestcluster.LocalTestCluster{
		// Large offset so that any value in the future is an uncertain read. Also
		// makes sure that the values we write in the future below don't actually
		// wind up in the past.
		Clock:     hlc.NewClock(hlc.UnixNano, 50*time.Second),
		DBContext: &dbCtx,
	}
	s.Start(t, testutils.NewNodeTestBaseContext(), InitSenderForLocalTestCluster)
	defer s.Stop()
	disableOwnNodeCertain(t, s)

	offsetNS := int64(100)
	keySlow := roachpb.Key("slow")
	keyFast := roachpb.Key("fast")
	valSlow := []byte("wols")
	valFast := []byte("tsaf")

	// Write keySlow at now+offset, keyFast at now+2*offset
	futureTS := s.Clock.Now()
	futureTS.WallTime += offsetNS
	val := roachpb.MakeValueFromBytes(valSlow)
	if err := engine.MVCCPut(context.Background(), s.Eng, nil, keySlow, futureTS, val, nil); err != nil {
		t.Fatal(err)
	}
	futureTS.WallTime += offsetNS
	val.SetBytes(valFast)
	if err := engine.MVCCPut(context.Background(), s.Eng, nil, keyFast, futureTS, val, nil); err != nil {
		t.Fatal(err)
	}

	i := 0
	if tErr := s.DB.Txn(context.TODO(), func(txn *client.Txn) error {
		i++
		// The first command serves to start a Txn, fixing the timestamps.
		// There will be a restart, but this is idempotent.
		if _, err := txn.Scan("t", roachpb.Key("t").Next(), 0); err != nil {
			t.Fatal(err)
		}
		// This is a bit of a hack for the sake of this test: By visiting the
		// node above, we've made a note of its clock, which allows us to
		// prevent the restart. But we want to catch the restart, so reset the
		// observed timestamps.
		txn.Proto.ResetObservedTimestamps()

		// The server's clock suddenly jumps ahead of keyFast's timestamp.
		s.Manual.Increment(2*offsetNS + 1)

		// Now read slowKey first. It should read at 0, catch an uncertainty error,
		// and get keySlow's timestamp in that error, but upgrade it to the larger
		// node clock (which is ahead of keyFast as well). If the last part does
		// not happen, the read of keyFast should fail (i.e. read nothing).
		// There will be exactly one restart here.
		if gr, err := txn.Get(keySlow); err != nil {
			if i != 1 {
				t.Fatalf("unexpected transaction error: %s", err)
			}
			return err
		} else if !gr.Exists() || !bytes.Equal(gr.ValueBytes(), valSlow) {
			t.Fatalf("read of %q returned %v, wanted value %q", keySlow, gr.Value, valSlow)
		}

		// The node should already be certain, so we expect no restart here
		// and to read the correct key.
		if gr, err := txn.Get(keyFast); err != nil {
			t.Fatalf("second Get failed with %s", err)
		} else if !gr.Exists() || !bytes.Equal(gr.ValueBytes(), valFast) {
			t.Fatalf("read of %q returned %v, wanted value %q", keyFast, gr.Value, valFast)
		}
		return nil
	}); tErr != nil {
		t.Fatal(tErr)
	}
}

func kv(k, v []byte) roachpb.KeyValue {
	return roachpb.KeyValue{
		Key:   k,
		Value: roachpb.MakeValueFromBytes(v),
	}
}