// RangeEvents gets the events from key to end in [startRev, endRev).
// If `end` is nil, the request only observes the events on key.
// If `end` is not nil, it observes the events on key range [key, range_end).
// Limit limits the number of events returned.
// If startRev <=0, rangeEvents returns events from the beginning of uncompacted history.
// If endRev <=0, it indicates there is no end revision.
//
// If the required start rev is compacted, ErrCompacted will be returned.
// If the required start rev has not happened, ErrFutureRev will be returned.
//
// RangeEvents returns events that satisfy the requirement (0 <= n <= limit).
// If events in the revision range have not all happened, it returns immeidately
// what is available.
// It also returns nextRev which indicates the start revision used for the following
// RangeEvents call. The nextRev could be smaller than the given endRev if the store
// has not progressed so far or it hits the event limit.
//
// TODO: return byte slices instead of events to avoid meaningless encode and decode.
func (s *store) RangeEvents(key, end []byte, limit, startRev, endRev int64) (evs []storagepb.Event, nextRev int64, err error) {
s.mu.Lock()
defer s.mu.Unlock()
if startRev > 0 && startRev <= s.compactMainRev {
return nil, 0, ErrCompacted
}
if startRev > s.currentRev.main {
return nil, 0, ErrFutureRev
}
revs := s.kvindex.RangeEvents(key, end, startRev)
if len(revs) == 0 {
return nil, s.currentRev.main + 1, nil
}
tx := s.b.BatchTx()
tx.Lock()
defer tx.Unlock()
// fetch events from the backend using revisions
for _, rev := range revs {
if endRev > 0 && rev.main >= endRev {
return evs, rev.main, nil
}
revbytes := newRevBytes()
revToBytes(rev, revbytes)
_, vs := tx.UnsafeRange(keyBucketName, revbytes, nil, 0)
if len(vs) != 1 {
log.Fatalf("storage: range cannot find rev (%d,%d)", rev.main, rev.sub)
}
e := storagepb.Event{}
if err := e.Unmarshal(vs[0]); err != nil {
log.Fatalf("storage: cannot unmarshal event: %v", err)
}
evs = append(evs, e)
if limit > 0 && len(evs) >= int(limit) {
return evs, rev.main + 1, nil
}
}
return evs, s.currentRev.main + 1, nil
}
