diff --git a/Godeps/Godeps.json b/Godeps/Godeps.json
index 08180fba9..065c61690 100644
--- a/Godeps/Godeps.json
+++ b/Godeps/Godeps.json
@@ -41,7 +41,7 @@
 		},
 		{
 			"ImportPath": "github.com/calmh/xdr",
-			"Rev": "e1714bbe4764b15490fcc8ebd25d4bd9ea50a4b9"
+			"Rev": "a597b63b87d6140f79084c8aab214b4d533833a1"
 		},
 		{
 			"ImportPath": "github.com/juju/ratelimit",
@@ -49,7 +49,7 @@
 		},
 		{
 			"ImportPath": "github.com/syndtr/goleveldb/leveldb",
-			"Rev": "17fd8940e0f778c27793a25bff8c48ddd7bf53ac"
+			"Rev": "59d87758aeaab5ab6ed289c773349500228a1557"
 		},
 		{
 			"ImportPath": "github.com/vitrun/qart/coding",
diff --git a/Godeps/_workspace/src/github.com/calmh/xdr/reader_ipdr.go b/Godeps/_workspace/src/github.com/calmh/xdr/reader_ipdr.go
index 2fda700b9..28e0b56ad 100644
--- a/Godeps/_workspace/src/github.com/calmh/xdr/reader_ipdr.go
+++ b/Godeps/_workspace/src/github.com/calmh/xdr/reader_ipdr.go
@@ -22,7 +22,7 @@ func (r *Reader) ReadUint8() uint8 {
 	}
 
 	if debug {
-		dl.Printf("rd uint8=%d (0x%08x)", r.b[0], r.b[0])
+		dl.Printf("rd uint8=%d (0x%02x)", r.b[0], r.b[0])
 	}
 	return r.b[0]
 }
@@ -43,7 +43,7 @@ func (r *Reader) ReadUint16() uint16 {
 	v := uint16(r.b[1]) | uint16(r.b[0])<<8
 
 	if debug {
-		dl.Printf("rd uint16=%d (0x%08x)", v, v)
+		dl.Printf("rd uint16=%d (0x%04x)", v, v)
 	}
 	return v
 }
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/bench_test.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/bench_test.go
index 295eebaef..91b426709 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/bench_test.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/bench_test.go
@@ -249,7 +249,9 @@ func (p *dbBench) newIter() iterator.Iterator {
 }
 
 func (p *dbBench) close() {
-	p.b.Log(p.db.s.tops.bpool)
+	if bp, err := p.db.GetProperty("leveldb.blockpool"); err == nil {
+		p.b.Log("Block pool stats: ", bp)
+	}
 	p.db.Close()
 	p.stor.Close()
 	os.RemoveAll(benchDB)
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/cache.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/cache.go
index d71fe1505..fe398f03a 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/cache.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/cache.go
@@ -11,84 +11,106 @@ import (
 	"sync/atomic"
 )
 
-// SetFunc used by Namespace.Get method to create a cache object. SetFunc
-// may return ok false, in that case the cache object will not be created.
-type SetFunc func() (ok bool, value interface{}, charge int, fin SetFin)
+// SetFunc is the function that will be called by Namespace.Get to create
+// a cache object, if charge is less than one than the cache object will
+// not be registered to cache tree, if value is nil then the cache object
+// will not be created.
+type SetFunc func() (charge int, value interface{})
 
-// SetFin will be called when corresponding cache object are released.
-type SetFin func()
+// DelFin is the function that will be called as the result of a delete operation.
+// Exist == true is indication that the object is exist, and pending == true is
+// indication of deletion already happen but haven't done yet (wait for all handles
+// to be released). And exist == false means the object doesn't exist.
+type DelFin func(exist, pending bool)
 
-// DelFin will be called when corresponding cache object are released.
-// DelFin will be called after SetFin. The exist is true if the corresponding
-// cache object is actually exist in the cache tree.
-type DelFin func(exist bool)
-
-// PurgeFin will be called when corresponding cache object are released.
-// PurgeFin will be called after SetFin. If PurgeFin present DelFin will
-// not be executed but passed to the PurgeFin, it is up to the caller
-// to call it or not.
-type PurgeFin func(ns, key uint64, delfin DelFin)
+// PurgeFin is the function that will be called as the result of a purge operation.
+type PurgeFin func(ns, key uint64)
 
 // Cache is a cache tree. A cache instance must be goroutine-safe.
 type Cache interface {
-	// SetCapacity sets cache capacity.
+	// SetCapacity sets cache tree capacity.
 	SetCapacity(capacity int)
 
-	// GetNamespace gets or creates a cache namespace for the given id.
+	// Capacity returns cache tree capacity.
+	Capacity() int
+
+	// Used returns used cache tree capacity.
+	Used() int
+
+	// Size returns entire alive cache objects size.
+	Size() int
+
+	// GetNamespace gets cache namespace with the given id.
+	// GetNamespace is never return nil.
 	GetNamespace(id uint64) Namespace
 
-	// Purge purges all cache namespaces, read Namespace.Purge method documentation.
+	// Purge purges all cache namespace from this cache tree.
+	// This is behave the same as calling Namespace.Purge method on all cache namespace.
 	Purge(fin PurgeFin)
 
-	// Zap zaps all cache namespaces, read Namespace.Zap method documentation.
-	Zap(closed bool)
+	// Zap detaches all cache namespace from this cache tree.
+	// This is behave the same as calling Namespace.Zap method on all cache namespace.
+	Zap()
 }
 
 // Namespace is a cache namespace. A namespace instance must be goroutine-safe.
 type Namespace interface {
-	// Get gets cache object for the given key. The given SetFunc (if not nil) will
-	// be called if the given key does not exist.
-	// If the given key does not exist, SetFunc is nil or SetFunc return ok false, Get
-	// will return ok false.
-	Get(key uint64, setf SetFunc) (obj Object, ok bool)
-
-	// Get deletes cache object for the given key. If exist the cache object will
-	// be deleted later when all of its handles have been released (i.e. no one use
-	// it anymore) and the given DelFin (if not nil) will finally be  executed. If
-	// such cache object does not exist the given DelFin will be executed anyway.
+	// Get gets cache object with the given key.
+	// If cache object is not found and setf is not nil, Get will atomically creates
+	// the cache object by calling setf. Otherwise Get will returns nil.
 	//
-	// Delete returns true if such cache object exist.
+	// The returned cache handle should be released after use by calling Release
+	// method.
+	Get(key uint64, setf SetFunc) Handle
+
+	// Delete removes cache object with the given key from cache tree.
+	// A deleted cache object will be released as soon as all of its handles have
+	// been released.
+	// Delete only happen once, subsequent delete will consider cache object doesn't
+	// exist, even if the cache object ins't released yet.
+	//
+	// If not nil, fin will be called if the cache object doesn't exist or when
+	// finally be released.
+	//
+	// Delete returns true if such cache object exist and never been deleted.
 	Delete(key uint64, fin DelFin) bool
 
-	// Purge deletes all cache objects, read Delete method documentation.
+	// Purge removes all cache objects within this namespace from cache tree.
+	// This is the same as doing delete on all cache objects.
+	//
+	// If not nil, fin will be called on all cache objects when its finally be
+	// released.
 	Purge(fin PurgeFin)
 
-	// Zap detaches the namespace from the cache tree and delete all its cache
-	// objects. The cache objects deletion and finalizers execution are happen
-	// immediately, even if its existing handles haven't yet been released.
-	// A zapped namespace can't never be filled again.
-	// If closed is false then the Get function will always call the given SetFunc
-	// if it is not nil, but resultant of the SetFunc will not be cached.
-	Zap(closed bool)
+	// Zap detaches namespace from cache tree and release all its cache objects.
+	// A zapped namespace can never be filled again.
+	// Calling Get on zapped namespace will always return nil.
+	Zap()
 }
 
-// Object is a cache object.
-type Object interface {
-	// Release releases the cache object. Other methods should not be called
-	// after the cache object has been released.
+// Handle is a cache handle.
+type Handle interface {
+	// Release releases this cache handle. This method can be safely called mutiple
+	// times.
 	Release()
 
-	// Value returns value of the cache object.
+	// Value returns value of this cache handle.
+	// Value will returns nil after this cache handle have be released.
 	Value() interface{}
 }
 
+const (
+	DelNotExist = iota
+	DelExist
+	DelPendig
+)
+
 // Namespace state.
 type nsState int
 
 const (
 	nsEffective nsState = iota
 	nsZapped
-	nsClosed
 )
 
 // Node state.
@@ -97,29 +119,29 @@ type nodeState int
 const (
 	nodeEffective nodeState = iota
 	nodeEvicted
-	nodeRemoved
+	nodeDeleted
 )
 
-// Fake object.
-type fakeObject struct {
+// Fake handle.
+type fakeHandle struct {
 	value interface{}
 	fin   func()
 	once  uint32
 }
 
-func (o *fakeObject) Value() interface{} {
-	if atomic.LoadUint32(&o.once) == 0 {
-		return o.value
+func (h *fakeHandle) Value() interface{} {
+	if atomic.LoadUint32(&h.once) == 0 {
+		return h.value
 	}
 	return nil
 }
 
-func (o *fakeObject) Release() {
-	if !atomic.CompareAndSwapUint32(&o.once, 0, 1) {
+func (h *fakeHandle) Release() {
+	if !atomic.CompareAndSwapUint32(&h.once, 0, 1) {
 		return
 	}
-	if o.fin != nil {
-		o.fin()
-		o.fin = nil
+	if h.fin != nil {
+		h.fin()
+		h.fin = nil
 	}
 }
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/cache_test.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/cache_test.go
index 07a9939b2..6735e02ef 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/cache_test.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/cache_test.go
@@ -7,15 +7,35 @@
 package cache
 
 import (
+	"fmt"
 	"math/rand"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
 	"testing"
+	"time"
 )
 
-func set(ns Namespace, key uint64, value interface{}, charge int, fin func()) Object {
-	obj, _ := ns.Get(key, func() (bool, interface{}, int, SetFin) {
-		return true, value, charge, fin
+type releaserFunc struct {
+	fn    func()
+	value interface{}
+}
+
+func (r releaserFunc) Release() {
+	if r.fn != nil {
+		r.fn()
+	}
+}
+
+func set(ns Namespace, key uint64, value interface{}, charge int, relf func()) Handle {
+	return ns.Get(key, func() (int, interface{}) {
+		if relf != nil {
+			return charge, releaserFunc{relf, value}
+		} else {
+			return charge, value
+		}
 	})
-	return obj
 }
 
 func TestCache_HitMiss(t *testing.T) {
@@ -43,29 +63,31 @@ func TestCache_HitMiss(t *testing.T) {
 			setfin++
 		}).Release()
 		for j, y := range cases {
-			r, ok := ns.Get(y.key, nil)
+			h := ns.Get(y.key, nil)
 			if j <= i {
 				// should hit
-				if !ok {
+				if h == nil {
 					t.Errorf("case '%d' iteration '%d' is miss", i, j)
-				} else if r.Value().(string) != y.value {
-					t.Errorf("case '%d' iteration '%d' has invalid value got '%s', want '%s'", i, j, r.Value().(string), y.value)
+				} else {
+					if x := h.Value().(releaserFunc).value.(string); x != y.value {
+						t.Errorf("case '%d' iteration '%d' has invalid value got '%s', want '%s'", i, j, x, y.value)
+					}
 				}
 			} else {
 				// should miss
-				if ok {
-					t.Errorf("case '%d' iteration '%d' is hit , value '%s'", i, j, r.Value().(string))
+				if h != nil {
+					t.Errorf("case '%d' iteration '%d' is hit , value '%s'", i, j, h.Value().(releaserFunc).value.(string))
 				}
 			}
-			if ok {
-				r.Release()
+			if h != nil {
+				h.Release()
 			}
 		}
 	}
 
 	for i, x := range cases {
 		finalizerOk := false
-		ns.Delete(x.key, func(exist bool) {
+		ns.Delete(x.key, func(exist, pending bool) {
 			finalizerOk = true
 		})
 
@@ -74,22 +96,24 @@ func TestCache_HitMiss(t *testing.T) {
 		}
 
 		for j, y := range cases {
-			r, ok := ns.Get(y.key, nil)
+			h := ns.Get(y.key, nil)
 			if j > i {
 				// should hit
-				if !ok {
+				if h == nil {
 					t.Errorf("case '%d' iteration '%d' is miss", i, j)
-				} else if r.Value().(string) != y.value {
-					t.Errorf("case '%d' iteration '%d' has invalid value got '%s', want '%s'", i, j, r.Value().(string), y.value)
+				} else {
+					if x := h.Value().(releaserFunc).value.(string); x != y.value {
+						t.Errorf("case '%d' iteration '%d' has invalid value got '%s', want '%s'", i, j, x, y.value)
+					}
 				}
 			} else {
 				// should miss
-				if ok {
-					t.Errorf("case '%d' iteration '%d' is hit, value '%s'", i, j, r.Value().(string))
+				if h != nil {
+					t.Errorf("case '%d' iteration '%d' is hit, value '%s'", i, j, h.Value().(releaserFunc).value.(string))
 				}
 			}
-			if ok {
-				r.Release()
+			if h != nil {
+				h.Release()
 			}
 		}
 	}
@@ -107,42 +131,42 @@ func TestLRUCache_Eviction(t *testing.T) {
 	set(ns, 3, 3, 1, nil).Release()
 	set(ns, 4, 4, 1, nil).Release()
 	set(ns, 5, 5, 1, nil).Release()
-	if r, ok := ns.Get(2, nil); ok { // 1,3,4,5,2
-		r.Release()
+	if h := ns.Get(2, nil); h != nil { // 1,3,4,5,2
+		h.Release()
 	}
 	set(ns, 9, 9, 10, nil).Release() // 5,2,9
 
-	for _, x := range []uint64{9, 2, 5, 1} {
-		r, ok := ns.Get(x, nil)
-		if !ok {
-			t.Errorf("miss for key '%d'", x)
+	for _, key := range []uint64{9, 2, 5, 1} {
+		h := ns.Get(key, nil)
+		if h == nil {
+			t.Errorf("miss for key '%d'", key)
 		} else {
-			if r.Value().(int) != int(x) {
-				t.Errorf("invalid value for key '%d' want '%d', got '%d'", x, x, r.Value().(int))
+			if x := h.Value().(int); x != int(key) {
+				t.Errorf("invalid value for key '%d' want '%d', got '%d'", key, key, x)
 			}
-			r.Release()
+			h.Release()
 		}
 	}
 	o1.Release()
-	for _, x := range []uint64{1, 2, 5} {
-		r, ok := ns.Get(x, nil)
-		if !ok {
-			t.Errorf("miss for key '%d'", x)
+	for _, key := range []uint64{1, 2, 5} {
+		h := ns.Get(key, nil)
+		if h == nil {
+			t.Errorf("miss for key '%d'", key)
 		} else {
-			if r.Value().(int) != int(x) {
-				t.Errorf("invalid value for key '%d' want '%d', got '%d'", x, x, r.Value().(int))
+			if x := h.Value().(int); x != int(key) {
+				t.Errorf("invalid value for key '%d' want '%d', got '%d'", key, key, x)
 			}
-			r.Release()
+			h.Release()
 		}
 	}
-	for _, x := range []uint64{3, 4, 9} {
-		r, ok := ns.Get(x, nil)
-		if ok {
-			t.Errorf("hit for key '%d'", x)
-			if r.Value().(int) != int(x) {
-				t.Errorf("invalid value for key '%d' want '%d', got '%d'", x, x, r.Value().(int))
+	for _, key := range []uint64{3, 4, 9} {
+		h := ns.Get(key, nil)
+		if h != nil {
+			t.Errorf("hit for key '%d'", key)
+			if x := h.Value().(int); x != int(key) {
+				t.Errorf("invalid value for key '%d' want '%d', got '%d'", key, key, x)
 			}
-			r.Release()
+			h.Release()
 		}
 	}
 }
@@ -153,16 +177,15 @@ func TestLRUCache_SetGet(t *testing.T) {
 	for i := 0; i < 200; i++ {
 		n := uint64(rand.Intn(99999) % 20)
 		set(ns, n, n, 1, nil).Release()
-		if p, ok := ns.Get(n, nil); ok {
-			if p.Value() == nil {
+		if h := ns.Get(n, nil); h != nil {
+			if h.Value() == nil {
 				t.Errorf("key '%d' contains nil value", n)
 			} else {
-				got := p.Value().(uint64)
-				if got != n {
-					t.Errorf("invalid value for key '%d' want '%d', got '%d'", n, n, got)
+				if x := h.Value().(uint64); x != n {
+					t.Errorf("invalid value for key '%d' want '%d', got '%d'", n, n, x)
 				}
 			}
-			p.Release()
+			h.Release()
 		} else {
 			t.Errorf("key '%d' doesn't exist", n)
 		}
@@ -176,31 +199,319 @@ func TestLRUCache_Purge(t *testing.T) {
 	o2 := set(ns1, 2, 2, 1, nil)
 	ns1.Purge(nil)
 	set(ns1, 3, 3, 1, nil).Release()
-	for _, x := range []uint64{1, 2, 3} {
-		r, ok := ns1.Get(x, nil)
-		if !ok {
-			t.Errorf("miss for key '%d'", x)
+	for _, key := range []uint64{1, 2, 3} {
+		h := ns1.Get(key, nil)
+		if h == nil {
+			t.Errorf("miss for key '%d'", key)
 		} else {
-			if r.Value().(int) != int(x) {
-				t.Errorf("invalid value for key '%d' want '%d', got '%d'", x, x, r.Value().(int))
+			if x := h.Value().(int); x != int(key) {
+				t.Errorf("invalid value for key '%d' want '%d', got '%d'", key, key, x)
 			}
-			r.Release()
+			h.Release()
 		}
 	}
 	o1.Release()
 	o2.Release()
-	for _, x := range []uint64{1, 2} {
-		r, ok := ns1.Get(x, nil)
-		if ok {
-			t.Errorf("hit for key '%d'", x)
-			if r.Value().(int) != int(x) {
-				t.Errorf("invalid value for key '%d' want '%d', got '%d'", x, x, r.Value().(int))
+	for _, key := range []uint64{1, 2} {
+		h := ns1.Get(key, nil)
+		if h != nil {
+			t.Errorf("hit for key '%d'", key)
+			if x := h.Value().(int); x != int(key) {
+				t.Errorf("invalid value for key '%d' want '%d', got '%d'", key, key, x)
 			}
-			r.Release()
+			h.Release()
 		}
 	}
 }
 
+type testingCacheObjectCounter struct {
+	created  uint32
+	released uint32
+}
+
+func (c *testingCacheObjectCounter) createOne() {
+	atomic.AddUint32(&c.created, 1)
+}
+
+func (c *testingCacheObjectCounter) releaseOne() {
+	atomic.AddUint32(&c.released, 1)
+}
+
+type testingCacheObject struct {
+	t   *testing.T
+	cnt *testingCacheObjectCounter
+
+	ns, key uint64
+
+	releaseCalled uint32
+}
+
+func (x *testingCacheObject) Release() {
+	if atomic.CompareAndSwapUint32(&x.releaseCalled, 0, 1) {
+		x.cnt.releaseOne()
+	} else {
+		x.t.Errorf("duplicate setfin NS#%d KEY#%s", x.ns, x.key)
+	}
+}
+
+func TestLRUCache_Finalizer(t *testing.T) {
+	const (
+		capacity   = 100
+		goroutines = 100
+		iterations = 10000
+		keymax     = 8000
+	)
+
+	runtime.GOMAXPROCS(runtime.NumCPU())
+	defer runtime.GOMAXPROCS(1)
+
+	wg := &sync.WaitGroup{}
+	cnt := &testingCacheObjectCounter{}
+
+	c := NewLRUCache(capacity)
+
+	type instance struct {
+		seed       int64
+		rnd        *rand.Rand
+		ns         uint64
+		effective  int32
+		handles    []Handle
+		handlesMap map[uint64]int
+
+		delete          bool
+		purge           bool
+		zap             bool
+		wantDel         int32
+		delfinCalledAll int32
+		delfinCalledEff int32
+		purgefinCalled  int32
+	}
+
+	instanceGet := func(p *instance, ns Namespace, key uint64) {
+		h := ns.Get(key, func() (charge int, value interface{}) {
+			to := &testingCacheObject{
+				t: t, cnt: cnt,
+				ns:  p.ns,
+				key: key,
+			}
+			atomic.AddInt32(&p.effective, 1)
+			cnt.createOne()
+			return 1, releaserFunc{func() {
+				to.Release()
+				atomic.AddInt32(&p.effective, -1)
+			}, to}
+		})
+		p.handles = append(p.handles, h)
+		p.handlesMap[key] = p.handlesMap[key] + 1
+	}
+	instanceRelease := func(p *instance, ns Namespace, i int) {
+		h := p.handles[i]
+		key := h.Value().(releaserFunc).value.(*testingCacheObject).key
+		if n := p.handlesMap[key]; n == 0 {
+			t.Fatal("key ref == 0")
+		} else if n > 1 {
+			p.handlesMap[key] = n - 1
+		} else {
+			delete(p.handlesMap, key)
+		}
+		h.Release()
+		p.handles = append(p.handles[:i], p.handles[i+1:]...)
+		p.handles[len(p.handles) : len(p.handles)+1][0] = nil
+	}
+
+	seeds := make([]int64, goroutines)
+	instances := make([]instance, goroutines)
+	for i := range instances {
+		p := &instances[i]
+		p.handlesMap = make(map[uint64]int)
+		if seeds[i] == 0 {
+			seeds[i] = time.Now().UnixNano()
+		}
+		p.seed = seeds[i]
+		p.rnd = rand.New(rand.NewSource(p.seed))
+		p.ns = uint64(i)
+		p.delete = i%6 == 0
+		p.purge = i%8 == 0
+		p.zap = i%12 == 0 || i%3 == 0
+	}
+
+	seedsStr := make([]string, len(seeds))
+	for i, seed := range seeds {
+		seedsStr[i] = fmt.Sprint(seed)
+	}
+	t.Logf("seeds := []int64{%s}", strings.Join(seedsStr, ", "))
+
+	// Get and release.
+	for i := range instances {
+		p := &instances[i]
+
+		wg.Add(1)
+		go func(p *instance) {
+			defer wg.Done()
+
+			ns := c.GetNamespace(p.ns)
+			for i := 0; i < iterations; i++ {
+				if len(p.handles) == 0 || p.rnd.Int()%2 == 0 {
+					instanceGet(p, ns, uint64(p.rnd.Intn(keymax)))
+				} else {
+					instanceRelease(p, ns, p.rnd.Intn(len(p.handles)))
+				}
+			}
+		}(p)
+	}
+	wg.Wait()
+
+	if used, cap := c.Used(), c.Capacity(); used > cap {
+		t.Errorf("Used > capacity, used=%d cap=%d", used, cap)
+	}
+
+	// Check effective objects.
+	for i := range instances {
+		p := &instances[i]
+		if int(p.effective) < len(p.handlesMap) {
+			t.Errorf("#%d effective objects < acquired handle, eo=%d ah=%d", i, p.effective, len(p.handlesMap))
+		}
+	}
+
+	if want := int(cnt.created - cnt.released); c.Size() != want {
+		t.Errorf("Invalid cache size, want=%d got=%d", want, c.Size())
+	}
+
+	// Delete and purge.
+	for i := range instances {
+		p := &instances[i]
+		p.wantDel = p.effective
+
+		wg.Add(1)
+		go func(p *instance) {
+			defer wg.Done()
+
+			ns := c.GetNamespace(p.ns)
+
+			if p.delete {
+				for key := uint64(0); key < keymax; key++ {
+					_, wantExist := p.handlesMap[key]
+					gotExist := ns.Delete(key, func(exist, pending bool) {
+						atomic.AddInt32(&p.delfinCalledAll, 1)
+						if exist {
+							atomic.AddInt32(&p.delfinCalledEff, 1)
+						}
+					})
+					if !gotExist && wantExist {
+						t.Errorf("delete on NS#%d KEY#%d not found", p.ns, key)
+					}
+				}
+
+				var delfinCalled int
+				for key := uint64(0); key < keymax; key++ {
+					func(key uint64) {
+						gotExist := ns.Delete(key, func(exist, pending bool) {
+							if exist && !pending {
+								t.Errorf("delete fin on NS#%d KEY#%d exist and not pending for deletion", p.ns, key)
+							}
+							delfinCalled++
+						})
+						if gotExist {
+							t.Errorf("delete on NS#%d KEY#%d found", p.ns, key)
+						}
+					}(key)
+				}
+				if delfinCalled != keymax {
+					t.Errorf("(2) #%d not all delete fin called, diff=%d", p.ns, keymax-delfinCalled)
+				}
+			}
+
+			if p.purge {
+				ns.Purge(func(ns, key uint64) {
+					atomic.AddInt32(&p.purgefinCalled, 1)
+				})
+			}
+		}(p)
+	}
+	wg.Wait()
+
+	if want := int(cnt.created - cnt.released); c.Size() != want {
+		t.Errorf("Invalid cache size, want=%d got=%d", want, c.Size())
+	}
+
+	// Release.
+	for i := range instances {
+		p := &instances[i]
+
+		if !p.zap {
+			wg.Add(1)
+			go func(p *instance) {
+				defer wg.Done()
+
+				ns := c.GetNamespace(p.ns)
+				for i := len(p.handles) - 1; i >= 0; i-- {
+					instanceRelease(p, ns, i)
+				}
+			}(p)
+		}
+	}
+	wg.Wait()
+
+	if want := int(cnt.created - cnt.released); c.Size() != want {
+		t.Errorf("Invalid cache size, want=%d got=%d", want, c.Size())
+	}
+
+	// Zap.
+	for i := range instances {
+		p := &instances[i]
+
+		if p.zap {
+			wg.Add(1)
+			go func(p *instance) {
+				defer wg.Done()
+
+				ns := c.GetNamespace(p.ns)
+				ns.Zap()
+
+				p.handles = nil
+				p.handlesMap = nil
+			}(p)
+		}
+	}
+	wg.Wait()
+
+	if want := int(cnt.created - cnt.released); c.Size() != want {
+		t.Errorf("Invalid cache size, want=%d got=%d", want, c.Size())
+	}
+
+	if notrel, used := int(cnt.created-cnt.released), c.Used(); notrel != used {
+		t.Errorf("Invalid used value, want=%d got=%d", notrel, used)
+	}
+
+	c.Purge(nil)
+
+	for i := range instances {
+		p := &instances[i]
+
+		if p.delete {
+			if p.delfinCalledAll != keymax {
+				t.Errorf("#%d not all delete fin called, purge=%v zap=%v diff=%d", p.ns, p.purge, p.zap, keymax-p.delfinCalledAll)
+			}
+			if p.delfinCalledEff != p.wantDel {
+				t.Errorf("#%d not all effective delete fin called, diff=%d", p.ns, p.wantDel-p.delfinCalledEff)
+			}
+			if p.purge && p.purgefinCalled > 0 {
+				t.Errorf("#%d some purge fin called, delete=%v zap=%v n=%d", p.ns, p.delete, p.zap, p.purgefinCalled)
+			}
+		} else {
+			if p.purge {
+				if p.purgefinCalled != p.wantDel {
+					t.Errorf("#%d not all purge fin called, delete=%v zap=%v diff=%d", p.ns, p.delete, p.zap, p.wantDel-p.purgefinCalled)
+				}
+			}
+		}
+	}
+
+	if cnt.created != cnt.released {
+		t.Errorf("Some cache object weren't released, created=%d released=%d", cnt.created, cnt.released)
+	}
+}
+
 func BenchmarkLRUCache_SetRelease(b *testing.B) {
 	capacity := b.N / 100
 	if capacity <= 0 {
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/empty_cache.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/empty_cache.go
deleted file mode 100644
index 1fbf81459..000000000
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/empty_cache.go
+++ /dev/null
@@ -1,246 +0,0 @@
-// Copyright (c) 2013, Suryandaru Triandana <syndtr@gmail.com>
-// All rights reserved.
-//
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package cache
-
-import (
-	"sync"
-	"sync/atomic"
-)
-
-type emptyCache struct {
-	sync.Mutex
-	table map[uint64]*emptyNS
-}
-
-// NewEmptyCache creates a new initialized empty cache.
-func NewEmptyCache() Cache {
-	return &emptyCache{
-		table: make(map[uint64]*emptyNS),
-	}
-}
-
-func (c *emptyCache) GetNamespace(id uint64) Namespace {
-	c.Lock()
-	defer c.Unlock()
-
-	if ns, ok := c.table[id]; ok {
-		return ns
-	}
-
-	ns := &emptyNS{
-		cache: c,
-		id:    id,
-		table: make(map[uint64]*emptyNode),
-	}
-	c.table[id] = ns
-	return ns
-}
-
-func (c *emptyCache) Purge(fin PurgeFin) {
-	c.Lock()
-	for _, ns := range c.table {
-		ns.purgeNB(fin)
-	}
-	c.Unlock()
-}
-
-func (c *emptyCache) Zap(closed bool) {
-	c.Lock()
-	for _, ns := range c.table {
-		ns.zapNB(closed)
-	}
-	c.table = make(map[uint64]*emptyNS)
-	c.Unlock()
-}
-
-func (*emptyCache) SetCapacity(capacity int) {}
-
-type emptyNS struct {
-	cache *emptyCache
-	id    uint64
-	table map[uint64]*emptyNode
-	state nsState
-}
-
-func (ns *emptyNS) Get(key uint64, setf SetFunc) (o Object, ok bool) {
-	ns.cache.Lock()
-
-	switch ns.state {
-	case nsZapped:
-		ns.cache.Unlock()
-		if setf == nil {
-			return
-		}
-
-		var value interface{}
-		var fin func()
-		ok, value, _, fin = setf()
-		if ok {
-			o = &fakeObject{
-				value: value,
-				fin:   fin,
-			}
-		}
-		return
-	case nsClosed:
-		ns.cache.Unlock()
-		return
-	}
-
-	n, ok := ns.table[key]
-	if ok {
-		n.ref++
-	} else {
-		if setf == nil {
-			ns.cache.Unlock()
-			return
-		}
-
-		var value interface{}
-		var fin func()
-		ok, value, _, fin = setf()
-		if !ok {
-			ns.cache.Unlock()
-			return
-		}
-
-		n = &emptyNode{
-			ns:     ns,
-			key:    key,
-			value:  value,
-			setfin: fin,
-			ref:    1,
-		}
-		ns.table[key] = n
-	}
-
-	ns.cache.Unlock()
-	o = &emptyObject{node: n}
-	return
-}
-
-func (ns *emptyNS) Delete(key uint64, fin DelFin) bool {
-	ns.cache.Lock()
-
-	if ns.state != nsEffective {
-		ns.cache.Unlock()
-		if fin != nil {
-			fin(false)
-		}
-		return false
-	}
-
-	n, ok := ns.table[key]
-	if !ok {
-		ns.cache.Unlock()
-		if fin != nil {
-			fin(false)
-		}
-		return false
-	}
-	n.delfin = fin
-	ns.cache.Unlock()
-	return true
-}
-
-func (ns *emptyNS) purgeNB(fin PurgeFin) {
-	if ns.state != nsEffective {
-		return
-	}
-	for _, n := range ns.table {
-		n.purgefin = fin
-	}
-}
-
-func (ns *emptyNS) Purge(fin PurgeFin) {
-	ns.cache.Lock()
-	ns.purgeNB(fin)
-	ns.cache.Unlock()
-}
-
-func (ns *emptyNS) zapNB(closed bool) {
-	if ns.state != nsEffective {
-		return
-	}
-	for _, n := range ns.table {
-		n.execFin()
-	}
-	if closed {
-		ns.state = nsClosed
-	} else {
-		ns.state = nsZapped
-	}
-	ns.table = nil
-}
-
-func (ns *emptyNS) Zap(closed bool) {
-	ns.cache.Lock()
-	ns.zapNB(closed)
-	delete(ns.cache.table, ns.id)
-	ns.cache.Unlock()
-}
-
-type emptyNode struct {
-	ns       *emptyNS
-	key      uint64
-	value    interface{}
-	ref      int
-	setfin   SetFin
-	delfin   DelFin
-	purgefin PurgeFin
-}
-
-func (n *emptyNode) execFin() {
-	if n.setfin != nil {
-		n.setfin()
-		n.setfin = nil
-	}
-	if n.purgefin != nil {
-		n.purgefin(n.ns.id, n.key, n.delfin)
-		n.delfin = nil
-		n.purgefin = nil
-	} else if n.delfin != nil {
-		n.delfin(true)
-		n.delfin = nil
-	}
-}
-
-func (n *emptyNode) evict() {
-	n.ns.cache.Lock()
-	n.ref--
-	if n.ref == 0 {
-		if n.ns.state == nsEffective {
-			// Remove elem.
-			delete(n.ns.table, n.key)
-			// Execute finalizer.
-			n.execFin()
-		}
-	} else if n.ref < 0 {
-		panic("leveldb/cache: emptyNode: negative node reference")
-	}
-	n.ns.cache.Unlock()
-}
-
-type emptyObject struct {
-	node *emptyNode
-	once uint32
-}
-
-func (o *emptyObject) Value() interface{} {
-	if atomic.LoadUint32(&o.once) == 0 {
-		return o.node.value
-	}
-	return nil
-}
-
-func (o *emptyObject) Release() {
-	if !atomic.CompareAndSwapUint32(&o.once, 0, 1) {
-		return
-	}
-	o.node.evict()
-	o.node = nil
-}
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/lru_cache.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/lru_cache.go
index 3c98e076b..a1504b159 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/lru_cache.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/cache/lru_cache.go
@@ -9,16 +9,17 @@ package cache
 import (
 	"sync"
 	"sync/atomic"
+
+	"github.com/syndtr/goleveldb/leveldb/util"
 )
 
 // lruCache represent a LRU cache state.
 type lruCache struct {
-	sync.Mutex
-
-	recent   lruNode
-	table    map[uint64]*lruNs
-	capacity int
-	size     int
+	mu         sync.Mutex
+	recent     lruNode
+	table      map[uint64]*lruNs
+	capacity   int
+	used, size int
 }
 
 // NewLRUCache creates a new initialized LRU cache with the given capacity.
@@ -32,57 +33,75 @@ func NewLRUCache(capacity int) Cache {
 	return c
 }
 
+func (c *lruCache) Capacity() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.capacity
+}
+
+func (c *lruCache) Used() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.used
+}
+
+func (c *lruCache) Size() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.size
+}
+
 // SetCapacity set cache capacity.
 func (c *lruCache) SetCapacity(capacity int) {
-	c.Lock()
+	c.mu.Lock()
 	c.capacity = capacity
 	c.evict()
-	c.Unlock()
+	c.mu.Unlock()
 }
 
 // GetNamespace return namespace object for given id.
 func (c *lruCache) GetNamespace(id uint64) Namespace {
-	c.Lock()
-	defer c.Unlock()
+	c.mu.Lock()
+	defer c.mu.Unlock()
 
-	if p, ok := c.table[id]; ok {
-		return p
+	if ns, ok := c.table[id]; ok {
+		return ns
 	}
 
-	p := &lruNs{
+	ns := &lruNs{
 		lru:   c,
 		id:    id,
 		table: make(map[uint64]*lruNode),
 	}
-	c.table[id] = p
-	return p
+	c.table[id] = ns
+	return ns
 }
 
 // Purge purge entire cache.
 func (c *lruCache) Purge(fin PurgeFin) {
-	c.Lock()
+	c.mu.Lock()
 	for _, ns := range c.table {
 		ns.purgeNB(fin)
 	}
-	c.Unlock()
+	c.mu.Unlock()
 }
 
-func (c *lruCache) Zap(closed bool) {
-	c.Lock()
+func (c *lruCache) Zap() {
+	c.mu.Lock()
 	for _, ns := range c.table {
-		ns.zapNB(closed)
+		ns.zapNB()
 	}
 	c.table = make(map[uint64]*lruNs)
-	c.Unlock()
+	c.mu.Unlock()
 }
 
 func (c *lruCache) evict() {
 	top := &c.recent
-	for n := c.recent.rPrev; c.size > c.capacity && n != top; {
+	for n := c.recent.rPrev; c.used > c.capacity && n != top; {
 		n.state = nodeEvicted
 		n.rRemove()
-		n.evictNB()
-		c.size -= n.charge
+		n.derefNB()
+		c.used -= n.charge
 		n = c.recent.rPrev
 	}
 }
@@ -94,170 +113,157 @@ type lruNs struct {
 	state nsState
 }
 
-func (ns *lruNs) Get(key uint64, setf SetFunc) (o Object, ok bool) {
-	lru := ns.lru
-	lru.Lock()
+func (ns *lruNs) Get(key uint64, setf SetFunc) Handle {
+	ns.lru.mu.Lock()
 
-	switch ns.state {
-	case nsZapped:
-		lru.Unlock()
-		if setf == nil {
-			return
-		}
-
-		var value interface{}
-		var fin func()
-		ok, value, _, fin = setf()
-		if ok {
-			o = &fakeObject{
-				value: value,
-				fin:   fin,
-			}
-		}
-		return
-	case nsClosed:
-		lru.Unlock()
-		return
+	if ns.state != nsEffective {
+		ns.lru.mu.Unlock()
+		return nil
 	}
 
-	n, ok := ns.table[key]
+	node, ok := ns.table[key]
 	if ok {
-		switch n.state {
+		switch node.state {
 		case nodeEvicted:
 			// Insert to recent list.
-			n.state = nodeEffective
-			n.ref++
-			lru.size += n.charge
-			lru.evict()
+			node.state = nodeEffective
+			node.ref++
+			ns.lru.used += node.charge
+			ns.lru.evict()
 			fallthrough
 		case nodeEffective:
-			// Bump to front
-			n.rRemove()
-			n.rInsert(&lru.recent)
+			// Bump to front.
+			node.rRemove()
+			node.rInsert(&ns.lru.recent)
 		}
-		n.ref++
+		node.ref++
 	} else {
 		if setf == nil {
-			lru.Unlock()
-			return
+			ns.lru.mu.Unlock()
+			return nil
 		}
 
-		var value interface{}
-		var charge int
-		var fin func()
-		ok, value, charge, fin = setf()
-		if !ok {
-			lru.Unlock()
-			return
+		charge, value := setf()
+		if value == nil {
+			ns.lru.mu.Unlock()
+			return nil
 		}
 
-		n = &lruNode{
+		node = &lruNode{
 			ns:     ns,
 			key:    key,
 			value:  value,
 			charge: charge,
-			setfin: fin,
-			ref:    2,
+			ref:    1,
 		}
-		ns.table[key] = n
-		n.rInsert(&lru.recent)
+		ns.table[key] = node
 
-		lru.size += charge
-		lru.evict()
+		if charge > 0 {
+			node.ref++
+			node.rInsert(&ns.lru.recent)
+			ns.lru.used += charge
+			ns.lru.size += charge
+			ns.lru.evict()
+		}
 	}
 
-	lru.Unlock()
-	o = &lruObject{node: n}
-	return
+	ns.lru.mu.Unlock()
+	return &lruHandle{node: node}
 }
 
 func (ns *lruNs) Delete(key uint64, fin DelFin) bool {
-	lru := ns.lru
-	lru.Lock()
+	ns.lru.mu.Lock()
 
 	if ns.state != nsEffective {
-		lru.Unlock()
 		if fin != nil {
-			fin(false)
+			fin(false, false)
 		}
+		ns.lru.mu.Unlock()
 		return false
 	}
 
-	n, ok := ns.table[key]
-	if !ok {
-		lru.Unlock()
+	node, exist := ns.table[key]
+	if !exist {
 		if fin != nil {
-			fin(false)
+			fin(false, false)
 		}
+		ns.lru.mu.Unlock()
 		return false
 	}
 
-	n.delfin = fin
-	switch n.state {
-	case nodeRemoved:
-		lru.Unlock()
+	switch node.state {
+	case nodeDeleted:
+		if fin != nil {
+			fin(true, true)
+		}
+		ns.lru.mu.Unlock()
 		return false
 	case nodeEffective:
-		lru.size -= n.charge
-		n.rRemove()
-		n.evictNB()
+		ns.lru.used -= node.charge
+		node.state = nodeDeleted
+		node.delfin = fin
+		node.rRemove()
+		node.derefNB()
+	default:
+		node.state = nodeDeleted
+		node.delfin = fin
 	}
-	n.state = nodeRemoved
 
-	lru.Unlock()
+	ns.lru.mu.Unlock()
 	return true
 }
 
 func (ns *lruNs) purgeNB(fin PurgeFin) {
-	lru := ns.lru
 	if ns.state != nsEffective {
 		return
 	}
 
-	for _, n := range ns.table {
-		n.purgefin = fin
-		if n.state == nodeEffective {
-			lru.size -= n.charge
-			n.rRemove()
-			n.evictNB()
+	for _, node := range ns.table {
+		switch node.state {
+		case nodeDeleted:
+		case nodeEffective:
+			ns.lru.used -= node.charge
+			node.state = nodeDeleted
+			node.purgefin = fin
+			node.rRemove()
+			node.derefNB()
+		default:
+			node.state = nodeDeleted
+			node.purgefin = fin
 		}
-		n.state = nodeRemoved
 	}
 }
 
 func (ns *lruNs) Purge(fin PurgeFin) {
-	ns.lru.Lock()
+	ns.lru.mu.Lock()
 	ns.purgeNB(fin)
-	ns.lru.Unlock()
+	ns.lru.mu.Unlock()
 }
 
-func (ns *lruNs) zapNB(closed bool) {
-	lru := ns.lru
+func (ns *lruNs) zapNB() {
 	if ns.state != nsEffective {
 		return
 	}
 
-	if closed {
-		ns.state = nsClosed
-	} else {
-		ns.state = nsZapped
-	}
-	for _, n := range ns.table {
-		if n.state == nodeEffective {
-			lru.size -= n.charge
-			n.rRemove()
+	ns.state = nsZapped
+
+	for _, node := range ns.table {
+		if node.state == nodeEffective {
+			ns.lru.used -= node.charge
+			node.rRemove()
 		}
-		n.state = nodeRemoved
-		n.execFin()
+		ns.lru.size -= node.charge
+		node.state = nodeDeleted
+		node.fin()
 	}
 	ns.table = nil
 }
 
-func (ns *lruNs) Zap(closed bool) {
-	ns.lru.Lock()
-	ns.zapNB(closed)
+func (ns *lruNs) Zap() {
+	ns.lru.mu.Lock()
+	ns.zapNB()
 	delete(ns.lru.table, ns.id)
-	ns.lru.Unlock()
+	ns.lru.mu.Unlock()
 }
 
 type lruNode struct {
@@ -270,7 +276,6 @@ type lruNode struct {
 	charge   int
 	ref      int
 	state    nodeState
-	setfin   SetFin
 	delfin   DelFin
 	purgefin PurgeFin
 }
@@ -284,7 +289,6 @@ func (n *lruNode) rInsert(at *lruNode) {
 }
 
 func (n *lruNode) rRemove() bool {
-	// only remove if not already removed
 	if n.rPrev == nil {
 		return false
 	}
@@ -297,58 +301,56 @@ func (n *lruNode) rRemove() bool {
 	return true
 }
 
-func (n *lruNode) execFin() {
-	if n.setfin != nil {
-		n.setfin()
-		n.setfin = nil
+func (n *lruNode) fin() {
+	if r, ok := n.value.(util.Releaser); ok {
+		r.Release()
 	}
 	if n.purgefin != nil {
-		n.purgefin(n.ns.id, n.key, n.delfin)
+		n.purgefin(n.ns.id, n.key)
 		n.delfin = nil
 		n.purgefin = nil
 	} else if n.delfin != nil {
-		n.delfin(true)
+		n.delfin(true, false)
 		n.delfin = nil
 	}
 }
 
-func (n *lruNode) evictNB() {
+func (n *lruNode) derefNB() {
 	n.ref--
 	if n.ref == 0 {
 		if n.ns.state == nsEffective {
-			// remove elem
+			// Remove elemement.
 			delete(n.ns.table, n.key)
-			// execute finalizer
-			n.execFin()
+			n.ns.lru.size -= n.charge
+			n.fin()
 		}
 	} else if n.ref < 0 {
 		panic("leveldb/cache: lruCache: negative node reference")
 	}
 }
 
-func (n *lruNode) evict() {
-	n.ns.lru.Lock()
-	n.evictNB()
-	n.ns.lru.Unlock()
+func (n *lruNode) deref() {
+	n.ns.lru.mu.Lock()
+	n.derefNB()
+	n.ns.lru.mu.Unlock()
 }
 
-type lruObject struct {
+type lruHandle struct {
 	node *lruNode
 	once uint32
 }
 
-func (o *lruObject) Value() interface{} {
-	if atomic.LoadUint32(&o.once) == 0 {
-		return o.node.value
+func (h *lruHandle) Value() interface{} {
+	if atomic.LoadUint32(&h.once) == 0 {
+		return h.node.value
 	}
 	return nil
 }
 
-func (o *lruObject) Release() {
-	if !atomic.CompareAndSwapUint32(&o.once, 0, 1) {
+func (h *lruHandle) Release() {
+	if !atomic.CompareAndSwapUint32(&h.once, 0, 1) {
 		return
 	}
-
-	o.node.evict()
-	o.node = nil
+	h.node.deref()
+	h.node = nil
 }
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db.go
index 1be8748d4..59b9017d3 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db.go
@@ -655,6 +655,8 @@ func (db *DB) GetSnapshot() (*Snapshot, error) {
 //		Returns statistics of the underlying DB.
 //	leveldb.sstables
 //		Returns sstables list for each level.
+//	leveldb.blockpool
+//		Returns block pool stats.
 func (db *DB) GetProperty(name string) (value string, err error) {
 	err = db.ok()
 	if err != nil {
@@ -700,6 +702,16 @@ func (db *DB) GetProperty(name string) (value string, err error) {
 				value += fmt.Sprintf("%d:%d[%q .. %q]\n", t.file.Num(), t.size, t.imin, t.imax)
 			}
 		}
+	case p == "blockpool":
+		value = fmt.Sprintf("%v", db.s.tops.bpool)
+	case p == "cachedblock":
+		if bc := db.s.o.GetBlockCache(); bc != nil {
+			value = fmt.Sprintf("%d", bc.Size())
+		} else {
+			value = "<nil>"
+		}
+	case p == "openedtables":
+		value = fmt.Sprintf("%d", db.s.tops.cache.Size())
 	default:
 		err = errors.New("leveldb: GetProperty: unknown property: " + name)
 	}
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/doc.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/doc.go
index ac9ea3d0c..53f13bb24 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/doc.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/doc.go
@@ -37,6 +37,16 @@
 //	err = iter.Error()
 //	...
 //
+// Iterate over subset of database content with a particular prefix:
+//	iter := db.NewIterator(util.BytesPrefix([]byte("foo-")), nil)
+//	for iter.Next() {
+//		// Use key/value.
+//		...
+//	}
+//	iter.Release()
+//	err = iter.Error()
+//	...
+//
 // Seek-then-Iterate:
 //
 // 	iter := db.NewIterator(nil, nil)
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/opt/options.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/opt/options.go
index b940ce427..241184481 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/opt/options.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/opt/options.go
@@ -31,9 +31,12 @@ const (
 type noCache struct{}
 
 func (noCache) SetCapacity(capacity int)               {}
+func (noCache) Capacity() int                          { return 0 }
+func (noCache) Used() int                              { return 0 }
+func (noCache) Size() int                              { return 0 }
 func (noCache) GetNamespace(id uint64) cache.Namespace { return nil }
 func (noCache) Purge(fin cache.PurgeFin)               {}
-func (noCache) Zap(closed bool)                        {}
+func (noCache) Zap()                                   {}
 
 var NoCache cache.Cache = noCache{}
 
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table.go
index 46dd599be..1c3ff3249 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table.go
@@ -7,6 +7,7 @@
 package leveldb
 
 import (
+	"io"
 	"sort"
 	"sync/atomic"
 
@@ -297,7 +298,7 @@ func (t *tOps) create() (*tWriter, error) {
 func (t *tOps) createFrom(src iterator.Iterator) (f *tFile, n int, err error) {
 	w, err := t.create()
 	if err != nil {
-		return f, n, err
+		return
 	}
 
 	defer func() {
@@ -322,33 +323,33 @@ func (t *tOps) createFrom(src iterator.Iterator) (f *tFile, n int, err error) {
 	return
 }
 
-// Opens table. It returns a cache object, which should
+type tableWrapper struct {
+	*table.Reader
+	closer io.Closer
+}
+
+func (tr tableWrapper) Release() {
+	tr.closer.Close()
+}
+
+// Opens table. It returns a cache handle, which should
 // be released after use.
-func (t *tOps) open(f *tFile) (c cache.Object, err error) {
+func (t *tOps) open(f *tFile) (ch cache.Handle, err error) {
 	num := f.file.Num()
-	c, ok := t.cacheNS.Get(num, func() (ok bool, value interface{}, charge int, fin cache.SetFin) {
+	ch = t.cacheNS.Get(num, func() (charge int, value interface{}) {
 		var r storage.Reader
 		r, err = f.file.Open()
 		if err != nil {
-			return
+			return 0, nil
 		}
 
-		o := t.s.o
-
-		var cacheNS cache.Namespace
-		if bc := o.GetBlockCache(); bc != nil {
-			cacheNS = bc.GetNamespace(num)
+		var bcacheNS cache.Namespace
+		if bc := t.s.o.GetBlockCache(); bc != nil {
+			bcacheNS = bc.GetNamespace(num)
 		}
-
-		ok = true
-		value = table.NewReader(r, int64(f.size), cacheNS, t.bpool, o)
-		charge = 1
-		fin = func() {
-			r.Close()
-		}
-		return
+		return 1, tableWrapper{table.NewReader(r, int64(f.size), bcacheNS, t.bpool, t.s.o), r}
 	})
-	if !ok && err == nil {
+	if ch == nil && err == nil {
 		err = ErrClosed
 	}
 	return
@@ -357,34 +358,34 @@ func (t *tOps) open(f *tFile) (c cache.Object, err error) {
 // Finds key/value pair whose key is greater than or equal to the
 // given key.
 func (t *tOps) find(f *tFile, key []byte, ro *opt.ReadOptions) (rkey, rvalue []byte, err error) {
-	c, err := t.open(f)
+	ch, err := t.open(f)
 	if err != nil {
 		return nil, nil, err
 	}
-	defer c.Release()
-	return c.Value().(*table.Reader).Find(key, ro)
+	defer ch.Release()
+	return ch.Value().(tableWrapper).Find(key, ro)
 }
 
 // Returns approximate offset of the given key.
 func (t *tOps) offsetOf(f *tFile, key []byte) (offset uint64, err error) {
-	c, err := t.open(f)
+	ch, err := t.open(f)
 	if err != nil {
 		return
 	}
-	_offset, err := c.Value().(*table.Reader).OffsetOf(key)
+	_offset, err := ch.Value().(tableWrapper).OffsetOf(key)
 	offset = uint64(_offset)
-	c.Release()
+	ch.Release()
 	return
 }
 
 // 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)
+	ch, err := t.open(f)
 	if err != nil {
 		return iterator.NewEmptyIterator(err)
 	}
-	iter := c.Value().(*table.Reader).NewIterator(slice, ro)
-	iter.SetReleaser(c)
+	iter := ch.Value().(tableWrapper).NewIterator(slice, ro)
+	iter.SetReleaser(ch)
 	return iter
 }
 
@@ -392,14 +393,16 @@ func (t *tOps) newIterator(f *tFile, slice *util.Range, ro *opt.ReadOptions) ite
 // no one use the the table.
 func (t *tOps) remove(f *tFile) {
 	num := f.file.Num()
-	t.cacheNS.Delete(num, func(exist bool) {
-		if err := f.file.Remove(); err != nil {
-			t.s.logf("table@remove removing @%d %q", num, err)
-		} else {
-			t.s.logf("table@remove removed @%d", num)
-		}
-		if bc := t.s.o.GetBlockCache(); bc != nil {
-			bc.GetNamespace(num).Zap(false)
+	t.cacheNS.Delete(num, func(exist, pending bool) {
+		if !pending {
+			if err := f.file.Remove(); err != nil {
+				t.s.logf("table@remove removing @%d %q", num, err)
+			} else {
+				t.s.logf("table@remove removed @%d", num)
+			}
+			if bc := t.s.o.GetBlockCache(); bc != nil {
+				bc.GetNamespace(num).Zap()
+			}
 		}
 	})
 }
@@ -407,7 +410,7 @@ func (t *tOps) remove(f *tFile) {
 // Closes the table ops instance. It will close all tables,
 // regadless still used or not.
 func (t *tOps) close() {
-	t.cache.Zap(true)
+	t.cache.Zap()
 }
 
 // Creates new initialized table ops instance.
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table/reader.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table/reader.go
index 0c62a3c62..f397ac4f8 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table/reader.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table/reader.go
@@ -37,6 +37,7 @@ func max(x, y int) int {
 }
 
 type block struct {
+	bpool          *util.BufferPool
 	cmp            comparer.BasicComparer
 	data           []byte
 	restartsLen    int
@@ -139,6 +140,14 @@ func (b *block) newIterator(slice *util.Range, inclLimit bool, cache util.Releas
 	return bi
 }
 
+func (b *block) Release() {
+	if b.bpool != nil {
+		b.bpool.Put(b.data)
+		b.bpool = nil
+	}
+	b.data = nil
+}
+
 type dir int
 
 const (
@@ -438,6 +447,7 @@ func (i *blockIter) Value() []byte {
 
 func (i *blockIter) Release() {
 	if i.dir > dirReleased {
+		i.block = nil
 		i.prevNode = nil
 		i.prevKeys = nil
 		i.key = nil
@@ -610,43 +620,25 @@ func (r *Reader) readFilterBlock(bh blockHandle, filter filter.Filter) (*filterB
 	return b, nil
 }
 
-type releaseBlock struct {
-	r *Reader
-	b *block
-}
-
-func (r releaseBlock) Release() {
-	if r.b.data != nil {
-		r.r.bpool.Put(r.b.data)
-		r.b.data = nil
-	}
-}
-
 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) {
+		cache := r.cache.Get(dataBH.offset, func() (charge int, value interface{}) {
 			if !fillCache {
-				return
+				return 0, nil
 			}
 			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
-				}
+			if err != nil {
+				return 0, nil
 			}
-			return
+			return int(dataBH.length), dataBlock
 		})
 		if err != nil {
 			return iterator.NewEmptyIterator(err)
 		}
-		if ok {
+		if cache != nil {
 			dataBlock := cache.Value().(*block)
 			if !dataBlock.checksum && (r.checksum || checksum) {
 				if !verifyChecksum(dataBlock.data) {
@@ -662,7 +654,7 @@ func (r *Reader) getDataIter(dataBH blockHandle, slice *util.Range, checksum, fi
 	if err != nil {
 		return iterator.NewEmptyIterator(err)
 	}
-	iter := dataBlock.newIterator(slice, false, releaseBlock{r, dataBlock})
+	iter := dataBlock.newIterator(slice, false, dataBlock)
 	return iter
 }
 
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/buffer_pool_legacy.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/buffer_pool_legacy.go
index 7b7331dea..957f953b5 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/buffer_pool_legacy.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/buffer_pool_legacy.go
@@ -26,6 +26,8 @@ type BufferPool struct {
 	baseline1 int
 	baseline2 int
 
+	get     uint32
+	put     uint32
 	less    uint32
 	equal   uint32
 	greater uint32
@@ -47,6 +49,8 @@ func (p *BufferPool) poolNum(n int) int {
 
 // Get returns buffer with length of n.
 func (p *BufferPool) Get(n int) []byte {
+	atomic.AddUint32(&p.get, 1)
+
 	poolNum := p.poolNum(n)
 	pool := p.pool[poolNum]
 	if poolNum == 0 {
@@ -112,6 +116,8 @@ func (p *BufferPool) Get(n int) []byte {
 
 // Put adds given buffer to the pool.
 func (p *BufferPool) Put(b []byte) {
+	atomic.AddUint32(&p.put, 1)
+
 	pool := p.pool[p.poolNum(cap(b))]
 	select {
 	case pool <- b:
@@ -121,8 +127,8 @@ func (p *BufferPool) Put(b []byte) {
 }
 
 func (p *BufferPool) String() string {
-	return fmt.Sprintf("BufferPool{B·%d Z·%v Zm·%v L·%d E·%d G·%d M·%d}",
-		p.baseline0, p.size, p.sizeMiss, p.less, p.equal, p.greater, p.miss)
+	return fmt.Sprintf("BufferPool{B·%d Z·%v Zm·%v G·%d P·%d <·%d =·%d >·%d M·%d}",
+		p.baseline0, p.size, p.sizeMiss, p.get, p.put, p.less, p.equal, p.greater, p.miss)
 }
 
 func (p *BufferPool) drain() {
diff --git a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/range.go b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/range.go
index da0583123..24891d529 100644
--- a/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/range.go
+++ b/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/util/range.go
@@ -14,3 +14,18 @@ type Range struct {
 	// Limit of the key range, not include in the range.
 	Limit []byte
 }
+
+// BytesPrefix returns key range that satisfy the given prefix.
+// This only applicable for the standard 'bytes comparer'.
+func BytesPrefix(prefix []byte) *Range {
+	var limit []byte
+	for i := len(prefix) - 1; i >= 0; i-- {
+		c := prefix[i]
+		if c < 0xff {
+			limit = make([]byte, i+1)
+			copy(limit, prefix)
+			limit[i] = c + 1
+		}
+	}
+	return &Range{prefix, limit}
+}