// ScanSnapshot returns up to max key/value objects starting from
// start (inclusive) and ending at end (non-inclusive) from the
// given snapshotID.
// Specify max=0 for unbounded scans.
func (r *RocksDB) ScanSnapshot(start, end Key, max int64, snapshotID string) ([]proto.RawKeyValue, error) {
snapshotHandle, ok := r.snapshots[snapshotID]
if !ok {
return nil, util.Errorf("snapshotID %s does not exist", snapshotID)
}
opts := C.rocksdb_readoptions_create()
C.rocksdb_readoptions_set_fill_cache(opts, 0)
C.rocksdb_readoptions_set_snapshot(opts, snapshotHandle)
defer C.rocksdb_readoptions_destroy(opts)
return r.scanInternal(start, end, max, opts)
}
// 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
}
// SetFillCache controls whether reads performed with this ReadOptions will
// fill the Cache of the server. It defaults to true.
//
// It is useful to turn this off on ReadOptions for DB.Iterator (and DB.Get)
// calls used in offline threads to prevent bulk scans from flushing out live
// user data in the cache.
//
// See also Options.SetCache
func (ro *ReadOptions) SetFillCache(b bool) {
C.rocksdb_readoptions_set_fill_cache(ro.Opt, boolToUchar(b))
}
// Should the "data block"/"index block"/"filter block" read for this
// iteration be cached in memory?
// Callers may wish to set this field to false for bulk scans.
// Default: true
func (self *ReadOptions) SetFillCache(value bool) {
C.rocksdb_readoptions_set_fill_cache(self.c, boolToChar(value))
}
// 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) ([]proto.RawKeyValue, error) {
opts := C.rocksdb_readoptions_create()
C.rocksdb_readoptions_set_fill_cache(opts, 0)
defer C.rocksdb_readoptions_destroy(opts)
return r.scanInternal(start, end, max, opts)
}
func (opt *ReadOptions) SetFillCache(fillCache bool) {
C.rocksdb_readoptions_set_fill_cache(opt.rOpt, boolToUchar(fillCache))
}