Example #1
0
// NewIterator returns an iterator for the snapshot of the uderlying DB.
// The returned iterator is not goroutine-safe, but it is safe to use
// multiple iterators concurrently, with each in a dedicated goroutine.
// It is also safe to use an iterator concurrently with modifying its
// underlying DB. The resultant key/value pairs are guaranteed to be
// consistent.
//
// Slice allows slicing the iterator to only contains keys in the given
// range. A nil Range.Start is treated as a key before all keys in the
// DB. And a nil Range.Limit is treated as a key after all keys in
// the DB.
//
// The iterator must be released after use, by calling Release method.
// Releasing the snapshot doesn't mean releasing the iterator too, the
// iterator would be still valid until released.
//
// Also read Iterator documentation of the leveldb/iterator package.
func (snap *Snapshot) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
	if err := snap.db.ok(); err != nil {
		return iterator.NewEmptyIterator(err)
	}
	snap.mu.Lock()
	defer snap.mu.Unlock()
	if snap.released {
		return iterator.NewEmptyIterator(ErrSnapshotReleased)
	}
	// Since iterator already hold version ref, it doesn't need to
	// hold snapshot ref.
	return snap.db.newIterator(snap.elem.seq, slice, ro)
}
Example #2
0
File: db.go Project: mrG7/escher
// NewIterator returns an iterator for the latest snapshot of the
// uderlying DB.
// The returned iterator is not goroutine-safe, but it is safe to use
// multiple iterators concurrently, with each in a dedicated goroutine.
// It is also safe to use an iterator concurrently with modifying its
// underlying DB. The resultant key/value pairs are guaranteed to be
// consistent.
//
// Slice allows slicing the iterator to only contains keys in the given
// range. A nil Range.Start is treated as a key before all keys in the
// DB. And a nil Range.Limit is treated as a key after all keys in
// the DB.
//
// The iterator must be released after use, by calling Release method.
//
// Also read Iterator documentation of the leveldb/iterator package.
func (db *DB) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
	if err := db.ok(); err != nil {
		return iterator.NewEmptyIterator(err)
	}

	snap := db.newSnapshot()
	defer snap.Release()
	return snap.NewIterator(slice, ro)
}
Example #3
0
File: table.go Project: mrG7/escher
// Creates an iterator from the given table.
func (t *tOps) newIterator(f *tFile, slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
	c, err := t.open(f)
	if err != nil {
		return iterator.NewEmptyIterator(err)
	}
	iter := c.Value().(*table.Reader).NewIterator(slice, ro)
	iter.SetReleaser(c)
	return iter
}
Example #4
0
func (r *Reader) getDataIter(dataBH blockHandle, slice *util.Range, checksum, fillCache bool) iterator.Iterator {
	if r.cache != nil {
		// Get/set block cache.
		var err error
		cache, ok := r.cache.Get(dataBH.offset, func() (ok bool, value interface{}, charge int, fin cache.SetFin) {
			if !fillCache {
				return
			}
			var dataBlock *block
			dataBlock, err = r.readBlock(dataBH, checksum)
			if err == nil {
				ok = true
				value = dataBlock
				charge = int(dataBH.length)
				fin = func() {
					r.bpool.Put(dataBlock.data)
					dataBlock.data = nil
				}
			}
			return
		})
		if err != nil {
			return iterator.NewEmptyIterator(err)
		}
		if ok {
			dataBlock := cache.Value().(*block)
			if !dataBlock.checksum && (r.checksum || checksum) {
				if !verifyChecksum(dataBlock.data) {
					return iterator.NewEmptyIterator(errors.New("leveldb/table: Reader: invalid block (checksum mismatch)"))
				}
				dataBlock.checksum = true
			}
			iter := dataBlock.newIterator(slice, false, cache)
			return iter
		}
	}
	dataBlock, err := r.readBlock(dataBH, checksum)
	if err != nil {
		return iterator.NewEmptyIterator(err)
	}
	iter := dataBlock.newIterator(slice, false, releaseBlock{r, dataBlock})
	return iter
}
Example #5
0
func (r *Reader) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
	if r.err != nil {
		return iterator.NewEmptyIterator(r.err)
	}

	index := &indexIter{
		blockIter:   *r.indexBlock.newIterator(slice, true, nil),
		tableReader: r,
		slice:       slice,
		checksum:    ro.GetStrict(opt.StrictBlockChecksum),
		fillCache:   !ro.GetDontFillCache(),
	}
	return iterator.NewIndexedIterator(index, r.strictIter || ro.GetStrict(opt.StrictIterator), false)
}
Example #6
0
func (i *indexIter) Get() iterator.Iterator {
	value := i.Value()
	if value == nil {
		return nil
	}
	dataBH, n := decodeBlockHandle(value)
	if n == 0 {
		return iterator.NewEmptyIterator(errors.New("leveldb/table: Reader: invalid table (bad data block handle)"))
	}
	var slice *util.Range
	if i.slice != nil && (i.blockIter.isFirst() || i.blockIter.isLast()) {
		slice = i.slice
	}
	return i.tableReader.getDataIter(dataBH, slice, i.checksum, i.fillCache)
}