// newSeriesFrontier furnishes a populated diskFrontier for a given
// fingerprint. A nil diskFrontier will be returned if the series cannot
// be found in the store.
func newSeriesFrontier(f model.Fingerprint, d diskFrontier, i leveldb.Iterator) (s *seriesFrontier, err error) {
var (
lowerSeek = firstSupertime
upperSeek = lastSupertime
)
// If the diskFrontier for this iterator says that the candidate fingerprint
// is outside of its seeking domain, there is no way that a seriesFrontier
// could be materialized. Simply bail.
if !d.ContainsFingerprint(f) {
return
}
// If we are either the first or the last key in the database, we need to use
// pessimistic boundary frontiers.
if f.Equal(d.firstFingerprint) {
lowerSeek = indexable.EncodeTime(d.firstSupertime)
}
if f.Equal(d.lastFingerprint) {
upperSeek = indexable.EncodeTime(d.lastSupertime)
}
key := &dto.SampleKey{
Fingerprint: f.ToDTO(),
Timestamp: upperSeek,
}
raw, err := coding.NewProtocolBuffer(key).Encode()
if err != nil {
panic(err)
}
i.Seek(raw)
if i.Key() == nil {
return
}
retrievedKey, err := extractSampleKey(i)
if err != nil {
panic(err)
}
retrievedFingerprint := model.NewFingerprintFromRowKey(*retrievedKey.Fingerprint.Signature)
// The returned fingerprint may not match if the original seek key lives
// outside of a metric's frontier. This is probable, for we are seeking to
// to the maximum allowed time, which could advance us to the next
// fingerprint.
//
//
if !retrievedFingerprint.Equal(f) {
i.Previous()
retrievedKey, err = extractSampleKey(i)
if err != nil {
panic(err)
}
retrievedFingerprint := model.NewFingerprintFromRowKey(*retrievedKey.Fingerprint.Signature)
// If the previous key does not match, we know that the requested
// fingerprint does not live in the database.
if !retrievedFingerprint.Equal(f) {
return
}
}
s = &seriesFrontier{
lastSupertime: indexable.DecodeTime(retrievedKey.Timestamp),
lastTime: time.Unix(*retrievedKey.LastTimestamp, 0),
}
key.Timestamp = lowerSeek
raw, err = coding.NewProtocolBuffer(key).Encode()
if err != nil {
panic(err)
}
i.Seek(raw)
retrievedKey, err = extractSampleKey(i)
if err != nil {
panic(err)
}
retrievedFingerprint = model.NewFingerprintFromRowKey(*retrievedKey.Fingerprint.Signature)
s.firstSupertime = indexable.DecodeTime(retrievedKey.Timestamp)
return
}
