Golang C.rocksdb_create_iterator类(方法)实例源码

func (db *DB) NewIterator() driver.IIterator {
	it := new(Iterator)

	it.it = C.rocksdb_create_iterator(db.db, db.iteratorOpts.Opt)

	return it
}

func (db *DB) NewIterator(opt *ReadOptions) *Iterator {
	var rOpt = db.rOpt
	if opt != nil && opt.rOpt != nil {
		rOpt = opt.rOpt
	}

	var iter = new(Iterator)
	iter.it = C.rocksdb_create_iterator(db.db, rOpt)

	return iter
}

// Scan returns up to max key/value objects starting from
// start (inclusive) and ending at end (non-inclusive).
// If max is zero then the number of key/values returned is unbounded.
func (r *RocksDB) Scan(start, end Key, max int64) ([]RawKeyValue, error) {
	var keyVals []RawKeyValue
	if bytes.Compare(start, end) >= 0 {
		return keyVals, nil
	}
	// In order to prevent content displacement, caching is disabled
	// when performing scans. Any options set within the shared read
	// options field that should be carried over needs to be set here
	// as well.
	opts := C.rocksdb_readoptions_create()
	C.rocksdb_readoptions_set_fill_cache(opts, 0)
	defer C.rocksdb_readoptions_destroy(opts)
	it := C.rocksdb_create_iterator(r.rdb, opts)
	defer C.rocksdb_iter_destroy(it)

	byteCount := len(start)
	if byteCount == 0 {
		// start=Key("") needs special treatment since we need
		// to access start[0] in an explicit seek.
		C.rocksdb_iter_seek_to_first(it)
	} else {
		C.rocksdb_iter_seek(it, bytesPointer(start), C.size_t(byteCount))
	}
	for i := int64(1); C.rocksdb_iter_valid(it) == 1; C.rocksdb_iter_next(it) {
		if max > 0 && i > max {
			break
		}
		var l C.size_t
		// The data returned by rocksdb_iter_{key,value} is not meant to be
		// freed by the client. It is a direct reference to the data managed
		// by the iterator, so it is copied instead of freed.
		data := C.rocksdb_iter_key(it, &l)
		k := C.GoBytes(unsafe.Pointer(data), C.int(l))
		if bytes.Compare(k, end) >= 0 {
			break
		}
		data = C.rocksdb_iter_value(it, &l)
		v := C.GoBytes(unsafe.Pointer(data), C.int(l))
		keyVals = append(keyVals, RawKeyValue{
			Key:   k,
			Value: v,
		})
		i++
	}
	// Check for any errors during iteration.
	var cErr *C.char
	C.rocksdb_iter_get_error(it, &cErr)
	if cErr != nil {
		return nil, charToErr(cErr)
	}
	return keyVals, nil
}

// scan returns up to max key/value objects starting from
// start (inclusive) and ending at end (non-inclusive).
// If max is zero then the number of key/values returned is unbounded.
func (r *RocksDB) scan(start, end Key, max int64) ([]KeyValue, error) {
	// In order to prevent content displacement, caching is disabled
	// when performing scans. Any options set within the shared read
	// options field that should be carried over needs to be set here
	// as well.
	opts := C.rocksdb_readoptions_create()
	C.rocksdb_readoptions_set_fill_cache(opts, 0)
	defer C.rocksdb_readoptions_destroy(opts)
	it := C.rocksdb_create_iterator(r.rdb, opts)
	defer C.rocksdb_iter_destroy(it)

	keyVals := []KeyValue{}
	C.rocksdb_iter_seek(it, (*C.char)(unsafe.Pointer(&start[0])), C.size_t(len(start)))
	for i := int64(1); C.rocksdb_iter_valid(it) == 1; C.rocksdb_iter_next(it) {
		if max > 0 && i > max {
			break
		}
		var l C.size_t
		// The data returned by rocksdb_iter_{key,value} is not meant to be
		// freed by the client. It is a direct reference to the data managed
		// by the iterator, so it is copied instead of freed.
		data := C.rocksdb_iter_key(it, &l)
		k := C.GoBytes(unsafe.Pointer(data), C.int(l))
		if bytes.Equal(k, end) {
			break
		}
		data = C.rocksdb_iter_value(it, &l)
		v := C.GoBytes(unsafe.Pointer(data), C.int(l))
		keyVals = append(keyVals, KeyValue{
			Key:   k,
			Value: Value{Bytes: v},
		})
		i++
	}
	// Check for any errors during iteration.
	var cErr *C.char
	C.rocksdb_iter_get_error(it, &cErr)
	if cErr != nil {
		return nil, charToErr(cErr)
	}
	return keyVals, nil
}

func (s *Snapshot) NewIterator() driver.IIterator {
	it := new(Iterator)
	it.it = C.rocksdb_create_iterator(s.db.db, s.db.iteratorOpts.Opt)
	return it

}

// NewIterator returns an Iterator over the the database that uses the
// ReadOptions given.
func (self *DB) NewIterator(opts *ReadOptions) *Iterator {
	cIter := C.rocksdb_create_iterator(self.c, opts.c)

	return NewNativeIterator(cIter)
}

// NewIterator returns an Iterator over the the database that uses the
// ReadOptions given.
//
// Often, this is used for large, offline bulk reads while serving live
// traffic. In that case, it may be wise to disable caching so that the data
// processed by the returned Iterator does not displace the already cached
// data. This can be done by calling SetFillCache(false) on the ReadOptions
// before passing it here.
//
// Similiarly, ReadOptions.SetSnapshot is also useful.
func (db *DB) NewIterator(ro *ReadOptions) *Iterator {
	it := C.rocksdb_create_iterator(db.Ldb, ro.Opt)
	return &Iterator{Iter: it}
}

// NewIterator returns an Iterator over the the database that uses the
// ReadOptions given.
func (db *DB) NewIterator(opts *ReadOptions) *Iterator {
	cIter := C.rocksdb_create_iterator(db.c, opts.c)
	return NewNativeIterator(unsafe.Pointer(cIter))
}