// 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
}
// SeekToFirst moves the iterator to the first key in the database, as defined
// by the Comparator in the ReadOptions used to create this Iterator.
//
// This method is safe to call when Valid returns false.
func (it *Iterator) SeekToFirst() {
C.rocksdb_iter_seek_to_first(it.Iter)
}
// SeekToFirst moves the iterator to the first key in the database.
func (i *Iterator) SeekToFirst() {
C.rocksdb_iter_seek_to_first(i.c)
}
// SeekToFirst moves the iterator to the first key in the database.
func (self *Iterator) SeekToFirst() {
C.rocksdb_iter_seek_to_first(self.c)
}
func (iter *Iterator) SeekToFirst() {
C.rocksdb_iter_seek_to_first(iter.it)
}