func (m *MemDB) NewSnapshot() (*Snapshot, error) {
buf := m.snapshots.MakeBuf()
defer m.snapshots.FreeBuf(buf)
// Stitch all local gclists from all writers to create snapshot gclist
var head, tail *skiplist.Node
for w := m.wlist; w != nil; w = w.next {
if tail == nil {
head = w.gchead
tail = w.gctail
} else if w.gchead != nil {
tail.GClink = w.gchead
tail = w.gctail
}
w.gchead = nil
w.gctail = nil
// Update global stats
m.store.Stats.Merge(&w.slSts1)
atomic.AddInt64(&m.itemsCount, w.count)
w.count = 0
}
snap := &Snapshot{db: m, sn: m.getCurrSn(), refCount: 1, count: m.ItemsCount()}
m.snapshots.Insert(unsafe.Pointer(snap), CompareSnapshot, buf, &m.snapshots.Stats)
snap.gclist = head
newSn := atomic.AddUint32(&m.currSn, 1)
if newSn == math.MaxUint32 {
return nil, ErrMaxSnapshotsLimitReached
}
return snap, nil
}
func (w *Writer) DeleteNode(x *skiplist.Node) (success bool) {
defer func() {
if success {
w.count -= 1
}
}()
x.GClink = nil
sn := w.getCurrSn()
gotItem := (*Item)(x.Item())
if gotItem.bornSn == sn {
success = w.store.DeleteNode(x, w.insCmp, w.buf, &w.slSts1)
barrier := w.store.GetAccesBarrier()
barrier.FlushSession(unsafe.Pointer(x))
return
}
success = atomic.CompareAndSwapUint32(&gotItem.deadSn, 0, sn)
if success {
if w.gctail == nil {
w.gctail = x
w.gchead = w.gctail
} else {
w.gctail.GClink = x
w.gctail = x
}
}
return
}
func (m *MemDB) Close() {
// Wait until all snapshot iterators have finished
for s := m.snapshots.GetStats(); int(s.NodeCount) != 0; s = m.snapshots.GetStats() {
time.Sleep(time.Millisecond)
}
m.hasShutdown = true
// Acquire gc chan ownership
// This will make sure that no other goroutine will write to gcchan
for !atomic.CompareAndSwapInt32(&m.isGCRunning, 0, 1) {
time.Sleep(time.Millisecond)
}
close(m.gcchan)
buf := dbInstances.MakeBuf()
defer dbInstances.FreeBuf(buf)
dbInstances.Delete(unsafe.Pointer(m), CompareMemDB, buf, &dbInstances.Stats)
if m.useMemoryMgmt {
buf := m.snapshots.MakeBuf()
defer m.snapshots.FreeBuf(buf)
m.shutdownWg1.Wait()
close(m.freechan)
m.shutdownWg2.Wait()
// Manually free up all nodes
iter := m.store.NewIterator(m.iterCmp, buf)
defer iter.Close()
var lastNode *skiplist.Node
iter.SeekFirst()
if iter.Valid() {
lastNode = iter.GetNode()
iter.Next()
}
for lastNode != nil {
m.freeItem((*Item)(lastNode.Item()))
m.store.FreeNode(lastNode, &m.store.Stats)
lastNode = nil
if iter.Valid() {
lastNode = iter.GetNode()
iter.Next()
}
}
}
}