// 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)
}
// 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)
}
// 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
}
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
}
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)
}
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)
}