Golang Iterator.Next方法代码示例

// Apply implements the Processor interface.
func (p *DeletionProcessor) Apply(sampleIterator leveldb.Iterator, samplesPersistence raw.Persistence, stopAt clientmodel.Timestamp, fingerprint *clientmodel.Fingerprint) (lastCurated clientmodel.Timestamp, err error) {
	var pendingBatch raw.Batch

	defer func() {
		if pendingBatch != nil {
			pendingBatch.Close()
		}
	}()

	sampleKeyDto, _ := p.dtoSampleKeys.Get()
	defer p.dtoSampleKeys.Give(sampleKeyDto)

	sampleKey, _ := p.sampleKeys.Get()
	defer p.sampleKeys.Give(sampleKey)

	if err = sampleIterator.Key(sampleKeyDto); err != nil {
		return
	}
	sampleKey.Load(sampleKeyDto)

	sampleValues := unmarshalValues(sampleIterator.RawValue(), nil)

	pendingMutations := 0

	for lastCurated.Before(stopAt) && sampleKey.Fingerprint.Equal(fingerprint) {
		switch {
		// Furnish a new pending batch operation if none is available.
		case pendingBatch == nil:
			pendingBatch = leveldb.NewBatch()

		// If there are no sample values to extract from the datastore,
		// let's continue extracting more values to use.  We know that
		// the time.Before() block would prevent us from going into
		// unsafe territory.
		case len(sampleValues) == 0:
			if !sampleIterator.Next() {
				return lastCurated, fmt.Errorf("illegal condition: invalid iterator on continuation")
			}

			if err = sampleIterator.Key(sampleKeyDto); err != nil {
				return
			}
			sampleKey.Load(sampleKeyDto)

			sampleValues = unmarshalValues(sampleIterator.RawValue(), nil)

		// If the number of pending mutations exceeds the allowed batch
		// amount, commit to disk and delete the batch.  A new one will
		// be recreated if necessary.
		case pendingMutations >= p.maximumMutationPoolBatch:
			err = samplesPersistence.Commit(pendingBatch)
			if err != nil {
				return
			}

			pendingMutations = 0

			pendingBatch.Close()
			pendingBatch = nil

		case !sampleKey.MayContain(stopAt):
			k := &dto.SampleKey{}
			sampleKey.Dump(k)
			pendingBatch.Drop(k)
			lastCurated = sampleKey.LastTimestamp
			sampleValues = metric.Values{}
			pendingMutations++

		case sampleKey.MayContain(stopAt):
			k := &dto.SampleKey{}
			sampleKey.Dump(k)
			pendingBatch.Drop(k)
			pendingMutations++

			sampleValues = sampleValues.TruncateBefore(stopAt)
			if len(sampleValues) > 0 {
				k := &dto.SampleKey{}
				sampleKey = buildSampleKey(fingerprint, sampleValues)
				sampleKey.Dump(k)
				lastCurated = sampleKey.FirstTimestamp
				v := marshalValues(sampleValues, nil)
				pendingBatch.PutRaw(k, v)
				pendingMutations++
			} else {
				lastCurated = sampleKey.LastTimestamp
			}

		default:
			err = fmt.Errorf("unhandled processing case")
		}
	}

	// This is not deferred due to the off-chance that a pre-existing commit
	// failed.
	if pendingBatch != nil && pendingMutations > 0 {
		err = samplesPersistence.Commit(pendingBatch)
		if err != nil {
			return
		}
//.........这里部分代码省略.........

func (t *tieredStorage) loadChunkAroundTime(iterator leveldb.Iterator, frontier *seriesFrontier, fingerprint model.Fingerprint, ts time.Time) (chunk []model.SamplePair) {
	var (
		targetKey = &dto.SampleKey{
			Fingerprint: fingerprint.ToDTO(),
		}
		foundKey   = &dto.SampleKey{}
		foundValue *dto.SampleValueSeries
	)

	// Limit the target key to be within the series' keyspace.
	if ts.After(frontier.lastSupertime) {
		targetKey.Timestamp = indexable.EncodeTime(frontier.lastSupertime)
	} else {
		targetKey.Timestamp = indexable.EncodeTime(ts)
	}

	// Try seeking to target key.
	rawKey, _ := coding.NewProtocolBuffer(targetKey).Encode()
	iterator.Seek(rawKey)

	foundKey, err := extractSampleKey(iterator)
	if err != nil {
		panic(err)
	}

	// Figure out if we need to rewind by one block.
	// Imagine the following supertime blocks with time ranges:
	//
	// Block 1: ft 1000 - lt 1009 <data>
	// Block 1: ft 1010 - lt 1019 <data>
	//
	// If we are aiming to find time 1005, we would first seek to the block with
	// supertime 1010, then need to rewind by one block by virtue of LevelDB
	// iterator seek behavior.
	//
	// Only do the rewind if there is another chunk before this one.
	rewound := false
	firstTime := indexable.DecodeTime(foundKey.Timestamp)
	if ts.Before(firstTime) && !frontier.firstSupertime.After(ts) {
		iterator.Previous()
		rewound = true
	}

	foundValue, err = extractSampleValues(iterator)
	if err != nil {
		panic(err)
	}

	// If we rewound, but the target time is still past the current block, return
	// the last value of the current (rewound) block and the entire next block.
	if rewound {
		foundKey, err = extractSampleKey(iterator)
		if err != nil {
			panic(err)
		}
		currentChunkLastTime := time.Unix(*foundKey.LastTimestamp, 0)

		if ts.After(currentChunkLastTime) {
			sampleCount := len(foundValue.Value)
			chunk = append(chunk, model.SamplePair{
				Timestamp: time.Unix(*foundValue.Value[sampleCount-1].Timestamp, 0),
				Value:     model.SampleValue(*foundValue.Value[sampleCount-1].Value),
			})
			// We know there's a next block since we have rewound from it.
			iterator.Next()

			foundValue, err = extractSampleValues(iterator)
			if err != nil {
				panic(err)
			}
		}
	}

	// Now append all the samples of the currently seeked block to the output.
	for _, sample := range foundValue.Value {
		chunk = append(chunk, model.SamplePair{
			Timestamp: time.Unix(*sample.Timestamp, 0),
			Value:     model.SampleValue(*sample.Value),
		})
	}

	return
}