membuffer: implement snapshot get and iterator for ART (#1467)

ref pingcap/tidb#55287

Signed-off-by: you06 <you1474600@gmail.com>

internal/unionstore/art/art.go

@@ -423,6 +423,11 @@ func (t *ART) InspectNode(addr arena.MemdbArenaAddr) (*artLeaf, arena.MemdbArena
 	return lf, lf.vAddr
 }
 
+// IsStaging returns whether the MemBuffer is in staging status.
+func (t *ART) IsStaging() bool {
+	return len(t.stages) > 0
+}
+
 // Checkpoint returns a checkpoint of ART.
 func (t *ART) Checkpoint() *arena.MemDBCheckpoint {
 	cp := t.allocator.vlogAllocator.Checkpoint()
@@ -471,7 +476,7 @@ func (t *ART) Cleanup(h int) {
 		return
 	}
 	if h < len(t.stages) {
-		panic(fmt.Sprintf("cannot cleanup staging buffer, h=%v, len(db.stages)=%v", h, len(t.stages)))
+		panic(fmt.Sprintf("cannot cleanup staging buffer, h=%v, len(tree.stages)=%v", h, len(t.stages)))
 	}
 
 	cp := &t.stages[h-1]
@@ -501,7 +506,8 @@ func (t *ART) Reset() {
 // DiscardValues releases the memory used by all values.
 // NOTE: any operation need value will panic after this function.
 func (t *ART) DiscardValues() {
-	panic("unimplemented")
+	t.vlogInvalid = true
+	t.allocator.vlogAllocator.Reset()
 }
 
 // InspectStage used to inspect the value updates in the given stage.
@@ -514,16 +520,35 @@ func (t *ART) InspectStage(handle int, f func([]byte, kv.KeyFlags, []byte)) {
 
 // SelectValueHistory select the latest value which makes `predicate` returns true from the modification history.
 func (t *ART) SelectValueHistory(key []byte, predicate func(value []byte) bool) ([]byte, error) {
-	panic("unimplemented")
+	_, x := t.search(key)
+	if x == nil {
+		return nil, tikverr.ErrNotExist
+	}
+	if x.vAddr.IsNull() {
+		// A flags only key, act as value not exists
+		return nil, tikverr.ErrNotExist
+	}
+	result := t.allocator.vlogAllocator.SelectValueHistory(x.vAddr, func(addr arena.MemdbArenaAddr) bool {
+		return predicate(t.allocator.vlogAllocator.GetValue(addr))
+	})
+	if result.IsNull() {
+		return nil, nil
+	}
+	return t.allocator.vlogAllocator.GetValue(result), nil
+
 }
 
-func (t *ART) SetMemoryFootprintChangeHook(fn func(uint64)) {
-	panic("unimplemented")
+func (t *ART) SetMemoryFootprintChangeHook(hook func(uint64)) {
+	innerHook := func() {
+		hook(t.allocator.nodeAllocator.Capacity() + t.allocator.vlogAllocator.Capacity())
+	}
+	t.allocator.nodeAllocator.SetMemChangeHook(innerHook)
+	t.allocator.vlogAllocator.SetMemChangeHook(innerHook)
 }
 
 // MemHookSet implements the MemBuffer interface.
 func (t *ART) MemHookSet() bool {
-	panic("unimplemented")
+	return t.allocator.nodeAllocator.MemHookSet()
 }
 
 // GetKeyByHandle returns key by handle.
@@ -544,10 +569,24 @@ func (t *ART) GetValueByHandle(handle arena.MemKeyHandle) ([]byte, bool) {
 	return t.allocator.vlogAllocator.GetValue(lf.vAddr), true
 }
 
+// GetEntrySizeLimit gets the size limit for each entry and total buffer.
+func (t *ART) GetEntrySizeLimit() (uint64, uint64) {
+	return t.entrySizeLimit, t.bufferSizeLimit
+}
+
 func (t *ART) SetEntrySizeLimit(entryLimit, bufferLimit uint64) {
 	t.entrySizeLimit, t.bufferSizeLimit = entryLimit, bufferLimit
 }
 
+// RemoveFromBuffer is a test function, not support yet.
 func (t *ART) RemoveFromBuffer(key []byte) {
 	panic("unimplemented")
 }
+
+func (t *ART) GetCacheHitCount() uint64 {
+	return 0
+}
+
+func (t *ART) GetCacheMissCount() uint64 {
+	return 0
+}

internal/unionstore/art/art_iterator.go

@@ -50,7 +50,10 @@ func (t *ART) iter(lowerBound, upperBound []byte, reverse, includeFlags bool) (*
 		inner: &baseIter{
 			allocator: &t.allocator,
 		},
-		currAddr: arena.BadAddr, // the default value of currAddr is not equal to any valid address
+		// the default value of currAddr is not equal to any valid address
+		// arena.BadAddr's idx is maxuint32 - 1, which is impossible in common cases,
+		// this avoids the initial value of currAddr equals to endAddr.
+		currAddr: arena.BadAddr,
 		endAddr:  arena.NullAddr,
 	}
 	it.init(lowerBound, upperBound)
@@ -84,6 +87,15 @@ func (it *Iterator) Value() []byte {
 	return it.tree.allocator.vlogAllocator.GetValue(it.currLeaf.vAddr)
 }
 
+// HasValue returns false if it is flags only.
+func (it *Iterator) HasValue() bool {
+	return !it.isFlagsOnly()
+}
+
+func (it *Iterator) isFlagsOnly() bool {
+	return it.currLeaf != nil && it.currLeaf.vAddr.IsNull()
+}
+
 func (it *Iterator) Next() error {
 	if !it.valid {
 		// iterate is finished

internal/unionstore/art/art_snapshot.go

@@ -14,30 +14,111 @@
 
 package art
 
-import "context"
+import (
+	"context"
 
-func (*ART) SnapshotGetter() *SnapshotGetter {
-	panic("unimplemented")
+	tikverr "github.com/tikv/client-go/v2/error"
+	"github.com/tikv/client-go/v2/internal/unionstore/arena"
+)
+
+func (t *ART) getSnapshot() arena.MemDBCheckpoint {
+	if len(t.stages) > 0 {
+		return t.stages[0]
+	}
+	return t.checkpoint()
 }
 
-func (*ART) SnapshotIter([]byte, []byte) *SnapshotIter {
-	panic("unimplemented")
+// SnapshotGetter returns a Getter for a snapshot of MemBuffer.
+func (t *ART) SnapshotGetter() *SnapGetter {
+	return &SnapGetter{
+		tree: t,
+		cp:   t.getSnapshot(),
+	}
 }
 
-func (*ART) SnapshotIterReverse([]byte, []byte) *SnapshotIter {
-	panic("unimplemented")
+// SnapshotIter returns an Iterator for a snapshot of MemBuffer.
+func (t *ART) SnapshotIter(start, end []byte) *SnapIter {
+	inner, err := t.Iter(start, end)
+	if err != nil {
+		panic(err)
+	}
+	it := &SnapIter{
+		Iterator: inner,
+		cp:       t.getSnapshot(),
+	}
+	for !it.setValue() && it.Valid() {
+		_ = it.Next()
+	}
+	return it
 }
 
-type SnapshotGetter struct{}
-
-func (s *SnapshotGetter) Get(context.Context, []byte) ([]byte, error) {
-	panic("unimplemented")
+// SnapshotIterReverse returns a reverse Iterator for a snapshot of MemBuffer.
+func (t *ART) SnapshotIterReverse(k, lowerBound []byte) *SnapIter {
+	inner, err := t.IterReverse(k, lowerBound)
+	if err != nil {
+		panic(err)
+	}
+	it := &SnapIter{
+		Iterator: inner,
+		cp:       t.getSnapshot(),
+	}
+	for !it.setValue() && it.valid {
+		_ = it.Next()
+	}
+	return it
 }
 
-type SnapshotIter struct{}
+type SnapGetter struct {
+	tree *ART
+	cp   arena.MemDBCheckpoint
+}
 
-func (i *SnapshotIter) Valid() bool   { panic("unimplemented") }
-func (i *SnapshotIter) Key() []byte   { panic("unimplemented") }
-func (i *SnapshotIter) Value() []byte { panic("unimplemented") }
-func (i *SnapshotIter) Next() error   { panic("unimplemented") }
-func (i *SnapshotIter) Close()        { panic("unimplemented") }
+func (snap *SnapGetter) Get(ctx context.Context, key []byte) ([]byte, error) {
+	addr, lf := snap.tree.search(key)
+	if addr.IsNull() {
+		return nil, tikverr.ErrNotExist
+	}
+	if lf.vAddr.IsNull() {
+		// A flags only key, act as value not exists
+		return nil, tikverr.ErrNotExist
+	}
+	v, ok := snap.tree.allocator.vlogAllocator.GetSnapshotValue(lf.vAddr, &snap.cp)
+	if !ok {
+		return nil, tikverr.ErrNotExist
+	}
+	return v, nil
+}
+
+type SnapIter struct {
+	*Iterator
+	value []byte
+	cp    arena.MemDBCheckpoint
+}
+
+func (i *SnapIter) Value() []byte {
+	return i.value
+}
+
+func (i *SnapIter) Next() error {
+	i.value = nil
+	for i.Valid() {
+		if err := i.Iterator.Next(); err != nil {
+			return err
+		}
+		if i.setValue() {
+			return nil
+		}
+	}
+	return nil
+}
+
+func (i *SnapIter) setValue() bool {
+	if !i.Valid() {
+		return false
+	}
+	if v, ok := i.tree.allocator.vlogAllocator.GetSnapshotValue(i.currLeaf.vAddr, &i.cp); ok {
+		i.value = v
+		return true
+	}
+	return false
+}

internal/unionstore/memdb.go

@@ -49,7 +49,7 @@ type MemDBCheckpoint = arena.MemDBCheckpoint
 
 type MemKeyHandle = arena.MemKeyHandle
 
-type MemDB = rbtDBWithContext
+type MemDB = artDBWithContext
 
-var NewMemDB = newRbtDBWithContext
-var NewMemDBWithContext = newRbtDBWithContext
+var NewMemDB = newArtDBWithContext
+var NewMemDBWithContext = newArtDBWithContext

internal/unionstore/memdb_art.go

@@ -12,7 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//nolint:unused
 package unionstore
 
 import (
@@ -36,7 +35,6 @@ type artDBWithContext struct {
 	skipMutex bool
 }
 
-//nolint:unused
 func newArtDBWithContext() *artDBWithContext {
 	return &artDBWithContext{ART: art.New()}
 }
@@ -118,7 +116,7 @@ func (db *artDBWithContext) FlushWait() error { return nil }
 
 // GetMemDB implements the MemBuffer interface.
 func (db *artDBWithContext) GetMemDB() *MemDB {
-	panic("unimplemented")
+	return db
 }
 
 // BatchGet returns the values for given keys from the MemBuffer.

internal/unionstore/memdb_rbt.go

@@ -42,6 +42,7 @@ func newRbtDBWithContext() *rbtDBWithContext {
 	}
 }
 
+//nolint:unused
 func (db *rbtDBWithContext) setSkipMutex(skip bool) {
 	db.skipMutex = skip
 }
@@ -125,7 +126,7 @@ func (db *rbtDBWithContext) FlushWait() error { return nil }
 
 // GetMemDB implements the MemBuffer interface.
 func (db *rbtDBWithContext) GetMemDB() *MemDB {
-	return db
+	return nil
 }
 
 // BatchGet returns the values for given keys from the MemBuffer.

internal/unionstore/memdb_test.go

@@ -995,6 +995,7 @@ func testUnsetTemporaryFlag(t *testing.T, buffer MemBuffer) {
 
 func TestSnapshotGetIter(t *testing.T) {
 	testSnapshotGetIter(t, newRbtDBWithContext())
+	testSnapshotGetIter(t, newArtDBWithContext())
 }
 
 func testSnapshotGetIter(t *testing.T, db MemBuffer) {
@@ -1089,21 +1090,19 @@ func testIterNoResult(t *testing.T, buffer MemBuffer) {
 	assert := assert.New(t)
 
 	assert.Nil(buffer.Set([]byte{1, 1}, []byte{1, 1}))
-	// Test lower bound and upper bound seek same position
-	iter, err := buffer.Iter([]byte{1, 0, 0}, []byte{1, 0, 1})
-	assert.Nil(err)
-	assert.False(iter.Valid())
-	iter, err = buffer.IterReverse([]byte{1, 0, 1}, []byte{1, 0, 0})
-	assert.Nil(err)
-	assert.False(iter.Valid())
-	// Test lower bound >= upper bound
-	iter, err = buffer.Iter([]byte{1, 0, 1}, []byte{1, 0, 0})
-	assert.Nil(err)
-	assert.False(iter.Valid())
-	iter, err = buffer.IterReverse([]byte{1, 0, 0}, []byte{1, 0, 1})
-	assert.Nil(err)
-	assert.False(iter.Valid())
-	iter, err = buffer.Iter([]byte{1, 1}, []byte{1, 1})
-	assert.Nil(err)
-	assert.False(iter.Valid())
+
+	checkFn := func(lowerBound, upperBound []byte) {
+		iter, err := buffer.Iter(lowerBound, upperBound)
+		assert.Nil(err)
+		assert.False(iter.Valid())
+		iter, err = buffer.IterReverse(upperBound, lowerBound)
+		assert.Nil(err)
+		assert.False(iter.Valid())
+	}
+
+	// Test lower bound and upper bound seek to the same position
+	checkFn([]byte{1, 1}, []byte{1, 1})
+	checkFn([]byte{1, 0, 0}, []byte{1, 0, 1})
+	// Test lower bound > upper bound
+	checkFn([]byte{1, 0, 1}, []byte{1, 0, 0})
 }