// 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)
}
func (r *Reader) getDataIter(dataBH blockHandle, slice *util.Range, verifyChecksum, fillCache bool) iterator.Iterator {
b, rel, err := r.readBlockCached(dataBH, verifyChecksum, fillCache)
if err != nil {
return iterator.NewEmptyIterator(err)
}
return r.newBlockIter(b, rel, slice, false)
}
// Creates an iterator from the given table.
func (t *tOps) newIterator(f *tFile, slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
ch, err := t.open(f)
if err != nil {
return iterator.NewEmptyIterator(err)
}
iter := ch.Value().(*table.Reader).NewIterator(slice, ro)
iter.SetReleaser(ch)
return iter
}
func (r *Reader) getDataIterErr(dataBH blockHandle, slice *util.Range, verifyChecksum, fillCache bool) iterator.Iterator {
r.mu.RLock()
defer r.mu.RUnlock()
if r.err != nil {
return iterator.NewEmptyIterator(r.err)
}
return r.getDataIter(dataBH, slice, verifyChecksum, fillCache)
}
// NewIterator creates an iterator from the table.
//
// 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
// table. And a nil Range.Limit is treated as a key after all keys in
// the table.
//
// The returned iterator is not goroutine-safe and should be released
// when not used.
//
// Also read Iterator documentation of the leveldb/iterator package.
func (r *Reader) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
r.mu.RLock()
defer r.mu.RUnlock()
if r.err != nil {
return iterator.NewEmptyIterator(r.err)
}
fillCache := !ro.GetDontFillCache()
indexBlock, rel, err := r.getIndexBlock(fillCache)
if err != nil {
return iterator.NewEmptyIterator(err)
}
index := &indexIter{
blockIter: r.newBlockIter(indexBlock, rel, slice, true),
tr: r,
slice: slice,
fillCache: !ro.GetDontFillCache(),
}
return iterator.NewIndexedIterator(index, opt.GetStrict(r.o, ro, opt.StrictReader))
}
func (i *indexIter) Get() iterator.Iterator {
value := i.Value()
if value == nil {
return nil
}
dataBH, n := decodeBlockHandle(value)
if n == 0 {
return iterator.NewEmptyIterator(i.tr.newErrCorruptedBH(i.tr.indexBH, "bad data block handle"))
}
var slice *util.Range
if i.slice != nil && (i.blockIter.isFirst() || i.blockIter.isLast()) {
slice = i.slice
}
return i.tr.getDataIterErr(dataBH, slice, i.tr.verifyChecksum, i.fillCache)
}