Decompose the interface

db.go

@@ -134,8 +134,9 @@ type DB struct {
 	rwtx     *Tx
 	txs      []*Tx
 
-	freelist     fl.Interface
-	freelistLoad sync.Once
+	freelist           fl.Interface
+	freelistLoad       sync.Once
+	freelistReadWriter fl.ReadWriter
 
 	pagePool sync.Pool
 
@@ -417,12 +418,13 @@ func (db *DB) getPageSizeFromSecondMeta() (int, bool, error) {
 func (db *DB) loadFreelist() {
 	db.freelistLoad.Do(func() {
 		db.freelist = newFreelist(db.FreelistType)
+		db.freelistReadWriter = fl.NewSortedSerializer()
 		if !db.hasSyncedFreelist() {
 			// Reconstruct free list by scanning the DB.
 			db.freelist.Init(db.freepages())
 		} else {
 			// Read free list from freelist page.
-			db.freelist.Read(db.page(db.meta().Freelist()))
+			db.freelistReadWriter.Read(db.freelist, db.page(db.meta().Freelist()))
 		}
 		db.stats.FreePageN = db.freelist.FreeCount()
 	})

internal/freelist/array.go

@@ -8,17 +8,14 @@ import (
 )
 
 type array struct {
-	*shared
-
 	ids []common.Pgid // all free and available free page ids.
 }
 
 func (f *array) Init(ids common.Pgids) {
 	f.ids = ids
-	f.reindex()
 }
 
-func (f *array) Allocate(txid common.Txid, n int) common.Pgid {
+func (f *array) alloc(txid common.Txid, n int, allocs *map[common.Pgid]common.Txid, cache *map[common.Pgid]struct{}) common.Pgid {
 	if len(f.ids) == 0 {
 		return 0
 	}
@@ -49,9 +46,9 @@ func (f *array) Allocate(txid common.Txid, n int) common.Pgid {
 
 			// Remove from the free cache.
 			for i := common.Pgid(0); i < common.Pgid(n); i++ {
-				delete(f.cache, initial+i)
+				delete(*cache, initial+i)
 			}
-			f.allocs[initial] = txid
+			(*allocs)[initial] = txid
 			return initial
 		}
 
@@ -64,7 +61,7 @@ func (f *array) FreeCount() int {
 	return len(f.ids)
 }
 
-func (f *array) freePageIds() common.Pgids {
+func (f *array) FreePageIds() common.Pgids {
 	return f.ids
 }
 
@@ -99,9 +96,5 @@ func (f *array) mergeSpans(ids common.Pgids) {
 }
 
 func NewArrayFreelist() Interface {
-	a := &array{
-		shared: newShared(),
-	}
-	a.Interface = a
-	return a
+	return newShared(&array{})
 }

internal/freelist/array_test.go

@@ -33,8 +33,8 @@ func TestFreelistArray_allocate(t *testing.T) {
 	if id := int(f.Allocate(1, 0)); id != 0 {
 		t.Fatalf("exp=0; got=%v", id)
 	}
-	if exp := common.Pgids([]common.Pgid{9, 18}); !reflect.DeepEqual(exp, f.freePageIds()) {
-		t.Fatalf("exp=%v; got=%v", exp, f.freePageIds())
+	if exp := common.Pgids([]common.Pgid{9, 18}); !reflect.DeepEqual(exp, f.FreePageIds()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.FreePageIds())
 	}
 
 	if id := int(f.Allocate(1, 1)); id != 9 {
@@ -46,7 +46,7 @@ func TestFreelistArray_allocate(t *testing.T) {
 	if id := int(f.Allocate(1, 1)); id != 0 {
 		t.Fatalf("exp=0; got=%v", id)
 	}
-	if exp := common.Pgids([]common.Pgid{}); !reflect.DeepEqual(exp, f.freePageIds()) {
-		t.Fatalf("exp=%v; got=%v", exp, f.freePageIds())
+	if exp := common.Pgids([]common.Pgid{}); !reflect.DeepEqual(exp, f.FreePageIds()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.FreePageIds())
 	}
 }

internal/freelist/freelist.go

@@ -6,36 +6,34 @@ import (
 
 type ReadWriter interface {
 	// Read calls Init with the page ids stored in the given page.
-	Read(page *common.Page)
+	Read(f Interface, page *common.Page)
 
 	// Write writes the freelist into the given page.
-	Write(page *common.Page)
+	Write(f Interface, page *common.Page)
 
 	// EstimatedWritePageSize returns the size of the freelist after serialization in Write.
 	// This should never underestimate the size.
-	EstimatedWritePageSize() int
+	EstimatedWritePageSize(f Interface) int
 }
 
-type Interface interface {
-	ReadWriter
-
+type allocator interface {
 	// Init initializes this freelist with the given list of pages.
 	Init(ids common.Pgids)
 
-	// Allocate tries to allocate the given number of contiguous pages
-	// from the free list pages. It returns the starting page ID if
-	// available; otherwise, it returns 0.
-	Allocate(txid common.Txid, numPages int) common.Pgid
-
-	// Count returns the number of free and pending pages.
-	Count() int
-
 	// FreeCount returns the number of free pages.
 	FreeCount() int
 
-	// PendingCount returns the number of pending pages.
-	PendingCount() int
+	// FreePageIds returns the IDs of all free pages.
+	FreePageIds() common.Pgids
 
+	// mergeSpans is merging the given pages into the freelist
+	mergeSpans(ids common.Pgids)
+
+	// TODO(thomas): this is necessary to decouple, but leaks internals
+	alloc(txid common.Txid, numPages int, allocs *map[common.Pgid]common.Txid, cache *map[common.Pgid]struct{}) common.Pgid
+}
+
+type txManager interface {
 	// AddReadonlyTXID adds a given read-only transaction id for pending page tracking.
 	AddReadonlyTXID(txid common.Txid)
 
@@ -45,6 +43,31 @@ type Interface interface {
 	// ReleasePendingPages releases any pages associated with closed read-only transactions.
 	ReleasePendingPages()
 
+	// pendingPageIds returns all pending pages by transaction id.
+	pendingPageIds() map[common.Txid]*txPending
+
+	// release moves all page ids for a transaction id (or older) to the freelist.
+	release(txId common.Txid)
+
+	// releaseRange moves pending pages allocated within an extent [begin,end] to the free list.
+	releaseRange(begin, end common.Txid)
+}
+
+type Interface interface {
+	allocator
+	txManager
+
+	// Allocate tries to allocate the given number of contiguous pages
+	// from the free list pages. It returns the starting page ID if
+	// available; otherwise, it returns 0.
+	Allocate(txid common.Txid, numPages int) common.Pgid
+
+	// Count returns the number of free and pending pages.
+	Count() int
+
+	// PendingCount returns the number of pending pages.
+	PendingCount() int
+
 	// Free releases a page and its overflow for a given transaction id.
 	// If the page is already free then a panic will occur.
 	Free(txId common.Txid, p *common.Page)
@@ -55,28 +78,9 @@ type Interface interface {
 	// Rollback removes the pages from a given pending tx.
 	Rollback(txId common.Txid)
 
-	// Copyall copies a list of all free ids and all pending ids in one sorted list.
-	// f.count returns the minimum length required for dst.
-	Copyall(dst []common.Pgid)
-
-	// Reload reads the freelist from a page and filters out pending items.
-	Reload(p *common.Page)
+	// List returns a list of all free ids and all pending ids in one sorted list.
+	List() common.Pgids
 
-	// NoSyncReload reads the freelist from Pgids and filters out pending items.
-	NoSyncReload(pgIds common.Pgids)
-
-	// freePageIds returns the IDs of all free pages.
-	freePageIds() common.Pgids
-
-	// pendingPageIds returns all pending pages by transaction id.
-	pendingPageIds() map[common.Txid]*txPending
-
-	// release moves all page ids for a transaction id (or older) to the freelist.
-	release(txId common.Txid)
-
-	// releaseRange moves pending pages allocated within an extent [begin,end] to the free list.
-	releaseRange(begin, end common.Txid)
-
-	// mergeSpans is merging the given pages into the freelist
-	mergeSpans(ids common.Pgids)
+	// Reload reads the freelist from Pgids and filters out pending items.
+	Reload(pgIds common.Pgids)
 }

internal/freelist/freelist_test.go

@@ -40,13 +40,13 @@ func TestFreelist_release(t *testing.T) {
 	f.Free(102, common.NewPage(39, 0, 0, 0))
 	f.release(100)
 	f.release(101)
-	if exp := common.Pgids([]common.Pgid{9, 12, 13}); !reflect.DeepEqual(exp, f.freePageIds()) {
-		t.Fatalf("exp=%v; got=%v", exp, f.freePageIds())
+	if exp := common.Pgids([]common.Pgid{9, 12, 13}); !reflect.DeepEqual(exp, f.FreePageIds()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.FreePageIds())
 	}
 
 	f.release(102)
-	if exp := common.Pgids([]common.Pgid{9, 12, 13, 39}); !reflect.DeepEqual(exp, f.freePageIds()) {
-		t.Fatalf("exp=%v; got=%v", exp, f.freePageIds())
+	if exp := common.Pgids([]common.Pgid{9, 12, 13, 39}); !reflect.DeepEqual(exp, f.FreePageIds()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.FreePageIds())
 	}
 }
 
@@ -173,8 +173,8 @@ func TestFreelist_releaseRange(t *testing.T) {
 			f.releaseRange(r.begin, r.end)
 		}
 
-		if exp := common.Pgids(c.wantFree); !reflect.DeepEqual(exp, f.freePageIds()) {
-			t.Errorf("exp=%v; got=%v for %s", exp, f.freePageIds(), c.title)
+		if exp := common.Pgids(c.wantFree); !reflect.DeepEqual(exp, f.FreePageIds()) {
+			t.Errorf("exp=%v; got=%v for %s", exp, f.FreePageIds(), c.title)
 		}
 	}
 }
@@ -194,11 +194,12 @@ func TestFreelist_read(t *testing.T) {
 
 	// Deserialize page into a freelist.
 	f := newTestFreelist()
-	f.Read(page)
+	s := SortedSerializer{}
+	s.Read(f, page)
 
 	// Ensure that there are two page ids in the freelist.
-	if exp := common.Pgids([]common.Pgid{23, 50}); !reflect.DeepEqual(exp, f.freePageIds()) {
-		t.Fatalf("exp=%v; got=%v", exp, f.freePageIds())
+	if exp := common.Pgids([]common.Pgid{23, 50}); !reflect.DeepEqual(exp, f.FreePageIds()) {
+		t.Fatalf("exp=%v; got=%v", exp, f.FreePageIds())
 	}
 }
 
@@ -207,21 +208,22 @@ func TestFreelist_write(t *testing.T) {
 	// Create a freelist and write it to a page.
 	var buf [4096]byte
 	f := newTestFreelist()
+	s := SortedSerializer{}
 
 	f.Init([]common.Pgid{12, 39})
 	f.pendingPageIds()[100] = &txPending{ids: []common.Pgid{28, 11}}
 	f.pendingPageIds()[101] = &txPending{ids: []common.Pgid{3}}
 	p := (*common.Page)(unsafe.Pointer(&buf[0]))
-	f.Write(p)
+	s.Write(f, p)
 
 	// Read the page back out.
 	f2 := newTestFreelist()
-	f2.Read(p)
+	s.Read(f2, p)
 
 	// Ensure that the freelist is correct.
 	// All pages should be present and in reverse order.
-	if exp := common.Pgids([]common.Pgid{3, 11, 12, 28, 39}); !reflect.DeepEqual(exp, f2.freePageIds()) {
-		t.Fatalf("exp=%v; got=%v", exp, f2.freePageIds())
+	if exp := common.Pgids([]common.Pgid{3, 11, 12, 28, 39}); !reflect.DeepEqual(exp, f2.FreePageIds()) {
+		t.Fatalf("exp=%v; got=%v", exp, f2.FreePageIds())
 	}
 }
 
@@ -258,15 +260,15 @@ func Test_freelist_ReadIDs_and_getFreePageIDs(t *testing.T) {
 
 	f.Init(exp)
 
-	if got := f.freePageIds(); !reflect.DeepEqual(exp, got) {
+	if got := f.FreePageIds(); !reflect.DeepEqual(exp, got) {
 		t.Fatalf("exp=%v; got=%v", exp, got)
 	}
 
 	f2 := newTestFreelist()
 	var exp2 []common.Pgid
 	f2.Init(exp2)
 
-	if got2 := f2.freePageIds(); !reflect.DeepEqual(got2, common.Pgids(exp2)) {
+	if got2 := f2.FreePageIds(); !reflect.DeepEqual(got2, common.Pgids(exp2)) {
 		t.Fatalf("exp2=%#v; got2=%#v", exp2, got2)
 	}
 

internal/freelist/hashmap.go

@@ -12,8 +12,6 @@ import (
 type pidSet map[common.Pgid]struct{}
 
 type hashMap struct {
-	*shared
-
 	freePagesCount uint64                 // count of free pages(hashmap version)
 	freemaps       map[uint64]pidSet      // key is the size of continuous pages(span), value is a set which contains the starting pgids of same size
 	forwardMap     map[common.Pgid]uint64 // key is start pgid, value is its span size
@@ -54,11 +52,9 @@ func (f *hashMap) Init(pgids common.Pgids) {
 	if size != 0 && start != 0 {
 		f.addSpan(start, size)
 	}
-
-	f.reindex()
 }
 
-func (f *hashMap) Allocate(txid common.Txid, n int) common.Pgid {
+func (f *hashMap) alloc(txid common.Txid, n int, allocs *map[common.Pgid]common.Txid, cache *map[common.Pgid]struct{}) common.Pgid {
 	if n == 0 {
 		return 0
 	}
@@ -69,10 +65,10 @@ func (f *hashMap) Allocate(txid common.Txid, n int) common.Pgid {
 			// remove the span
 			f.delSpan(pid, uint64(n))
 
-			f.allocs[pid] = txid
+			(*allocs)[pid] = txid
 
 			for i := common.Pgid(0); i < common.Pgid(n); i++ {
-				delete(f.cache, pid+i)
+				delete(*cache, pid+i)
 			}
 			return pid
 		}
@@ -88,15 +84,15 @@ func (f *hashMap) Allocate(txid common.Txid, n int) common.Pgid {
 			// remove the initial
 			f.delSpan(pid, size)
 
-			f.allocs[pid] = txid
+			(*allocs)[pid] = txid
 
 			remain := size - uint64(n)
 
 			// add remain span
 			f.addSpan(pid+common.Pgid(n), remain)
 
 			for i := common.Pgid(0); i < common.Pgid(n); i++ {
-				delete(f.cache, pid+i)
+				delete(*cache, pid+i)
 			}
 			return pid
 		}
@@ -114,7 +110,7 @@ func (f *hashMap) FreeCount() int {
 	return int(f.freePagesCount)
 }
 
-func (f *hashMap) freePageIds() common.Pgids {
+func (f *hashMap) FreePageIds() common.Pgids {
 	count := f.FreeCount()
 	if count == 0 {
 		return nil
@@ -280,13 +276,14 @@ func (f *hashMap) idsFromBackwardMap() map[common.Pgid]struct{} {
 	return ids
 }
 
-func NewHashMapFreelist() Interface {
-	hm := &hashMap{
-		shared:      newShared(),
+func newHashMap() *hashMap {
+	return &hashMap{
 		freemaps:    make(map[uint64]pidSet),
 		forwardMap:  make(map[common.Pgid]uint64),
 		backwardMap: make(map[common.Pgid]uint64),
 	}
-	hm.Interface = hm
-	return hm
+}
+
+func NewHashMapFreelist() Interface {
+	return newShared(newHashMap())
 }