Merge pull request #206 from Shopify/pending_page_stats

Split the freelist page count stats to free and pending

db.go

@@ -559,7 +559,8 @@ func (db *DB) allocate(count int) (*page, error) {
 // Stats represents statistics about the database.
 type Stats struct {
 	// Freelist stats
-	FreePageN     int // total number of free pages
+	FreePageN     int // total number of free pages on the freelist
+	PendingPageN  int // total number of pending pages on the freelist
 	FreeAlloc     int // total bytes allocated in free pages
 	FreelistInuse int // total bytes used by the freelist
 

db_test.go

@@ -254,7 +254,8 @@ func TestDB_Stats(t *testing.T) {
 		})
 		stats := db.Stats()
 		assert.Equal(t, 2, stats.TxStats.PageCount, "PageCount")
-		assert.Equal(t, 2, stats.FreePageN, "FreelistN")
+		assert.Equal(t, 0, stats.FreePageN, "FreePageN")
+		assert.Equal(t, 2, stats.PendingPageN, "PendingPageN")
 	})
 }
 

freelist.go

@@ -27,7 +27,17 @@ func (f *freelist) size() int {
 
 // count returns count of pages on the freelist
 func (f *freelist) count() int {
-	var count = len(f.ids)
+	return f.free_count() + f.pending_count()
+}
+
+// free_count returns count of free pages
+func (f *freelist) free_count() int {
+	return len(f.ids)
+}
+
+// pending_count returns count of pending pages
+func (f *freelist) pending_count() int {
+	var count int
 	for _, list := range f.pending {
 		count += len(list)
 	}

tx.go

@@ -233,7 +233,8 @@ func (tx *Tx) rollback() {
 func (tx *Tx) close() {
 	if tx.writable {
 		// Grab freelist stats.
-		var freelistN = tx.db.freelist.count()
+		var freelistFreeN = tx.db.freelist.free_count()
+		var freelistPendingN = tx.db.freelist.pending_count()
 		var freelistAlloc = tx.db.freelist.size()
 
 		// Remove writer lock.
@@ -241,8 +242,9 @@ func (tx *Tx) close() {
 
 		// Merge statistics.
 		tx.db.statlock.Lock()
-		tx.db.stats.FreePageN = freelistN
-		tx.db.stats.FreeAlloc = freelistN * tx.db.pageSize
+		tx.db.stats.FreePageN = freelistFreeN
+		tx.db.stats.PendingPageN = freelistPendingN
+		tx.db.stats.FreeAlloc = (freelistFreeN + freelistPendingN) * tx.db.pageSize
 		tx.db.stats.FreelistInuse = freelistAlloc
 		tx.db.stats.TxStats.add(&tx.stats)
 		tx.db.statlock.Unlock()