*: remove MemBuffer cache and Release method. (pingcap#1411)

ddl/index.go

@@ -365,8 +365,6 @@ func (d *ddl) getSnapshotRows(t table.Table, version uint64, seekHandle int64) (
 		return nil, errors.Trace(err)
 	}
 
-	defer snap.Release()
-
 	firstKey := t.RecordKey(seekHandle)
 
 	it, err := snap.Seek(firstKey)

inspectkv/inspectkv.go

@@ -294,7 +294,6 @@ func ScanSnapshotTableRecord(store kv.Storage, ver kv.Version, t table.Table, st
 	if err != nil {
 		return nil, 0, errors.Trace(err)
 	}
-	defer snap.Release()
 
 	records, nextHandle, err := ScanTableRecord(snap, t, startHandle, limit)
 

kv/buffer_store.go

@@ -20,7 +20,6 @@ import (
 // BufferStore wraps a Retriever for read and a MemBuffer for buffered write.
 // Common usage pattern:
 //	bs := NewBufferStore(r) // use BufferStore to wrap a Retriever
-//	defer bs.Release()      // make sure it will be released
 //	// ...
 //	// read/write on bs
 //	// ...

kv/kv.go

@@ -63,12 +63,8 @@ type RetrieverMutator interface {
 	Mutator
 }
 
-// MemBuffer is an in-memory kv collection. It should be released after use.
-type MemBuffer interface {
-	RetrieverMutator
-	// Release releases the buffer.
-	Release()
-}
+// MemBuffer is an in-memory kv collection, can be used to buffer write operations.
+type MemBuffer RetrieverMutator
 
 // Transaction defines the interface for operations inside a Transaction.
 // This is not thread safe.
@@ -156,8 +152,6 @@ type Snapshot interface {
 	Retriever
 	// BatchGet gets a batch of values from snapshot.
 	BatchGet(keys []Key) (map[string][]byte, error)
-	// Release releases the snapshot to store.
-	Release()
 }
 
 // Driver is the interface that must be implemented by a KV storage.

kv/mem_buffer_test.go

@@ -46,10 +46,9 @@ func (s *testKVSuite) SetUpSuite(c *C) {
 	s.bs[1] = NewMemDbBuffer()
 }
 
-func (s *testKVSuite) TearDownSuite(c *C) {
-	for _, buffer := range s.bs {
-		buffer.Release()
-	}
+func (s *testKVSuite) ResetMembuffers() {
+	s.bs[0] = NewRBTreeBuffer()
+	s.bs[1] = NewMemDbBuffer()
 }
 
 func insertData(c *C, buffer MemBuffer) {
@@ -142,8 +141,8 @@ func (s *testKVSuite) TestGetSet(c *C) {
 	for _, buffer := range s.bs {
 		insertData(c, buffer)
 		mustGet(c, buffer)
-		buffer.Release()
 	}
+	s.ResetMembuffers()
 }
 
 func (s *testKVSuite) TestNewIterator(c *C) {
@@ -156,8 +155,8 @@ func (s *testKVSuite) TestNewIterator(c *C) {
 
 		insertData(c, buffer)
 		checkNewIterator(c, buffer)
-		buffer.Release()
 	}
+	s.ResetMembuffers()
 }
 
 func (s *testKVSuite) TestBasicNewIterator(c *C) {
@@ -166,7 +165,6 @@ func (s *testKVSuite) TestBasicNewIterator(c *C) {
 		it, err := buffer.Seek([]byte("2"))
 		c.Assert(err, IsNil)
 		c.Assert(it.Valid(), IsFalse)
-		buffer.Release()
 	}
 }
 
@@ -200,9 +198,8 @@ func (s *testKVSuite) TestNewIteratorMin(c *C) {
 		it, err = buffer.Seek([]byte("DATA_test_main_db_tbl_tbl_test_record__00000000000000000000"))
 		c.Assert(err, IsNil)
 		c.Assert(string(it.Key()), Equals, "DATA_test_main_db_tbl_tbl_test_record__00000000000000000001")
-
-		buffer.Release()
 	}
+	s.ResetMembuffers()
 }
 
 var opCnt = 100000
@@ -214,7 +211,6 @@ func BenchmarkRBTreeBufferSequential(b *testing.B) {
 	}
 	buffer := NewRBTreeBuffer()
 	benchmarkSetGet(b, buffer, data)
-	buffer.Release()
 	b.ReportAllocs()
 }
 
@@ -226,7 +222,6 @@ func BenchmarkRBTreeBufferRandom(b *testing.B) {
 	shuffle(data)
 	buffer := NewRBTreeBuffer()
 	benchmarkSetGet(b, buffer, data)
-	buffer.Release()
 	b.ReportAllocs()
 }
 
@@ -237,7 +232,6 @@ func BenchmarkMemDbBufferSequential(b *testing.B) {
 	}
 	buffer := NewMemDbBuffer()
 	benchmarkSetGet(b, buffer, data)
-	buffer.Release()
 	b.ReportAllocs()
 }
 
@@ -249,36 +243,31 @@ func BenchmarkMemDbBufferRandom(b *testing.B) {
 	shuffle(data)
 	buffer := NewMemDbBuffer()
 	benchmarkSetGet(b, buffer, data)
-	buffer.Release()
 	b.ReportAllocs()
 }
 
 func BenchmarkRBTreeIter(b *testing.B) {
 	buffer := NewRBTreeBuffer()
 	benchIterator(b, buffer)
-	buffer.Release()
 	b.ReportAllocs()
 }
 
 func BenchmarkMemDbIter(b *testing.B) {
 	buffer := NewMemDbBuffer()
 	benchIterator(b, buffer)
-	buffer.Release()
 	b.ReportAllocs()
 }
 
 func BenchmarkRBTreeCreation(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		buffer := NewRBTreeBuffer()
-		buffer.Release()
+		NewRBTreeBuffer()
 	}
 	b.ReportAllocs()
 }
 
 func BenchmarkMemDbCreation(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		buffer := NewMemDbBuffer()
-		buffer.Release()
+		NewMemDbBuffer()
 	}
 	b.ReportAllocs()
 }

kv/memdb_buffer.go

@@ -86,11 +86,6 @@ func (m *memDbBuffer) Delete(k Key) error {
 	return errors.Trace(err)
 }
 
-// Release reset the buffer.
-func (m *memDbBuffer) Release() {
-	m.db.Reset()
-}
-
 // Next implements the Iterator Next.
 func (i *memDbIter) Next() error {
 	if i.reverse {

kv/rbtree_buffer.go

@@ -85,11 +85,6 @@ func (m *rbTreeBuffer) Delete(k Key) error {
 	return nil
 }
 
-// Release reset the buffer.
-func (m *rbTreeBuffer) Release() {
-	m.tree = llrb.New()
-}
-
 // Next implements the Iterator Next.
 func (i *rbTreeIter) Next() error {
 	i.pair = nil

kv/union_store.go

@@ -44,12 +44,6 @@ type Options interface {
 	Get(opt Option) (v interface{}, ok bool)
 }
 
-var (
-	p = newCache("memdb pool", 100, func() MemBuffer {
-		return NewMemDbBuffer()
-	})
-)
-
 // conditionPair is used to store lazy check condition.
 // If condition not match (value is not equal as expected one), returns err.
 type conditionPair struct {
@@ -77,6 +71,28 @@ func NewUnionStore(snapshot Snapshot) UnionStore {
 	}
 }
 
+// invalidIterator implements Iterator interface.
+// It is used for read-only transaction which has no data written, the iterator is always invalid.
+type invalidIterator struct{}
+
+func (it invalidIterator) Valid() bool {
+	return false
+}
+
+func (it invalidIterator) Next() error {
+	return nil
+}
+
+func (it invalidIterator) Key() Key {
+	return nil
+}
+
+func (it invalidIterator) Value() []byte {
+	return nil
+}
+
+func (it invalidIterator) Close() {}
+
 type lazyMemBuffer struct {
 	mb MemBuffer
 }
@@ -91,46 +107,34 @@ func (lmb *lazyMemBuffer) Get(k Key) ([]byte, error) {
 
 func (lmb *lazyMemBuffer) Set(key Key, value []byte) error {
 	if lmb.mb == nil {
-		lmb.mb = p.get()
+		lmb.mb = NewMemDbBuffer()
 	}
 
 	return lmb.mb.Set(key, value)
 }
 
 func (lmb *lazyMemBuffer) Delete(k Key) error {
 	if lmb.mb == nil {
-		lmb.mb = p.get()
+		lmb.mb = NewMemDbBuffer()
 	}
 
 	return lmb.mb.Delete(k)
 }
 
 func (lmb *lazyMemBuffer) Seek(k Key) (Iterator, error) {
 	if lmb.mb == nil {
-		lmb.mb = p.get()
+		return invalidIterator{}, nil
 	}
-
 	return lmb.mb.Seek(k)
 }
 
 func (lmb *lazyMemBuffer) SeekReverse(k Key) (Iterator, error) {
 	if lmb.mb == nil {
-		lmb.mb = p.get()
+		return invalidIterator{}, nil
 	}
 	return lmb.mb.SeekReverse(k)
 }
 
-func (lmb *lazyMemBuffer) Release() {
-	if lmb.mb == nil {
-		return
-	}
-
-	lmb.mb.Release()
-
-	p.put(lmb.mb)
-	lmb.mb = nil
-}
-
 // Get implements the Retriever interface.
 func (us *unionStore) Get(k Key) ([]byte, error) {
 	v, err := us.MemBuffer.Get(k)
@@ -205,12 +209,6 @@ func (us *unionStore) DelOption(opt Option) {
 	delete(us.opts, opt)
 }
 
-// Release implements the UnionStore Release interface.
-func (us *unionStore) Release() {
-	us.snapshot.Release()
-	us.BufferStore.Release()
-}
-
 type options map[Option]interface{}
 
 func (opts options) Get(opt Option) (interface{}, bool) {

kv/union_store_test.go

@@ -32,10 +32,6 @@ func (s *testUnionStoreSuite) SetUpTest(c *C) {
 	s.us = NewUnionStore(&mockSnapshot{s.store})
 }
 
-func (s *testUnionStoreSuite) TearDownTest(c *C) {
-	s.us.Release()
-}
-
 func (s *testUnionStoreSuite) TestGetSet(c *C) {
 	defer testleak.AfterTest(c)()
 	s.store.Set([]byte("1"), []byte("1"))
@@ -173,7 +169,3 @@ func (s *mockSnapshot) Seek(k Key) (Iterator, error) {
 func (s *mockSnapshot) SeekReverse(k Key) (Iterator, error) {
 	return s.store.SeekReverse(k)
 }
-
-func (s *mockSnapshot) Release() {
-	s.store.Release()
-}

store/localstore/mvcc_test.go

@@ -176,7 +176,6 @@ func (t *testMvccSuite) TestSnapshotGet(c *C) {
 	testKey := encodeTestDataKey(1)
 
 	snapshot, err := t.s.GetSnapshot(kv.MaxVersion)
-	defer snapshot.Release()
 	b, err = snapshot.Get(testKey)
 	c.Assert(err, IsNil)
 	c.Assert(string(b), Equals, "new")

store/localstore/snapshot.go

@@ -157,9 +157,6 @@ func (s *dbSnapshot) SeekReverse(k kv.Key) (kv.Iterator, error) {
 	return it, errors.Trace(err)
 }
 
-func (s *dbSnapshot) Release() {
-}
-
 type dbIter struct {
 	s       *dbSnapshot
 	valid   bool

store/localstore/txn.go

@@ -119,7 +119,6 @@ func (txn *dbTxn) Commit() error {
 }
 
 func (txn *dbTxn) close() error {
-	txn.us.Release()
 	txn.lockedKeys = nil
 	txn.valid = false
 	return nil