Change fill percent to be per-bucket.

This commit moves the DB.FillPercent field to Bucket.FillPercent. This
allows the fill percentage to be specified per-bucket, per-tx. This
value is not persisted and should be set whenever using it.

bucket.go

@@ -23,6 +23,15 @@ const (
 
 const bucketHeaderSize = int(unsafe.Sizeof(bucket{}))
 
+const (
+	minFillPercent = 0.1
+	maxFillPercent = 1.0
+)
+
+// DefaultFillPercent is the percentage that split pages are filled.
+// This value can be changed by setting Bucket.FillPercent.
+const DefaultFillPercent = 0.5
+
 // Bucket represents a collection of key/value pairs inside the database.
 type Bucket struct {
 	*bucket
@@ -31,6 +40,11 @@ type Bucket struct {
 	page     *page              // inline page reference
 	rootNode *node              // materialized node for the root page.
 	nodes    map[pgid]*node     // node cache
+
+	// Sets the threshold for filling nodes when they split. By default,
+	// the bucket will fill to 50% but it can be useful to increase this
+	// amount if you know that your write workloads are mostly append-only.
+	FillPercent float64
 }
 
 // bucket represents the on-file representation of a bucket.
@@ -44,7 +58,7 @@ type bucket struct {
 
 // newBucket returns a new bucket associated with a transaction.
 func newBucket(tx *Tx) Bucket {
-	var b = Bucket{tx: tx}
+	var b = Bucket{tx: tx, FillPercent: DefaultFillPercent}
 	if tx.writable {
 		b.buckets = make(map[string]*Bucket)
 		b.nodes = make(map[pgid]*node)
@@ -155,7 +169,11 @@ func (b *Bucket) CreateBucket(key []byte) (*Bucket, error) {
 	}
 
 	// Create empty, inline bucket.
-	var bucket = Bucket{bucket: &bucket{}, rootNode: &node{isLeaf: true}}
+	var bucket = Bucket{
+		bucket:      &bucket{},
+		rootNode:    &node{isLeaf: true},
+		FillPercent: DefaultFillPercent,
+	}
 	var value = bucket.write()
 
 	// Insert into node.

bucket_test.go

@@ -674,8 +674,6 @@ func TestBucket_Stats_RandomFill(t *testing.T) {
 	}
 
 	withOpenDB(func(db *DB, path string) {
-		db.FillPercent = 0.9
-
 		// Add a set of values in random order. It will be the same random
 		// order so we can maintain consistency between test runs.
 		var count int
@@ -683,6 +681,7 @@ func TestBucket_Stats_RandomFill(t *testing.T) {
 		for _, i := range r.Perm(1000) {
 			db.Update(func(tx *Tx) error {
 				b, _ := tx.CreateBucketIfNotExists([]byte("woojits"))
+				b.FillPercent = 0.9
 				for _, j := range r.Perm(100) {
 					index := (j * 10000) + i
 					b.Put([]byte(fmt.Sprintf("%d000000000000000", index)), []byte("0000000000"))

cmd/bolt/bench.go

@@ -47,7 +47,6 @@ func Bench(options *BenchOptions) {
 		return
 	}
 	db.NoSync = options.NoSync
-	db.FillPercent = options.FillPercent
 	defer db.Close()
 
 	// Enable streaming stats.
@@ -140,6 +139,7 @@ func benchWriteWithSource(db *bolt.DB, options *BenchOptions, results *BenchResu
 	for i := 0; i < options.Iterations; i += options.BatchSize {
 		err := db.Update(func(tx *bolt.Tx) error {
 			b, _ := tx.CreateBucketIfNotExists(benchBucketName)
+			b.FillPercent = options.FillPercent
 
 			for j := 0; j < options.BatchSize; j++ {
 				var key = make([]byte, options.KeySize)
@@ -165,10 +165,12 @@ func benchWriteNestedWithSource(db *bolt.DB, options *BenchOptions, results *Ben
 	for i := 0; i < options.Iterations; i += options.BatchSize {
 		err := db.Update(func(tx *bolt.Tx) error {
 			top, _ := tx.CreateBucketIfNotExists(benchBucketName)
+			top.FillPercent = options.FillPercent
 
 			var name = make([]byte, options.KeySize)
 			binary.BigEndian.PutUint32(name, keySource())
 			b, _ := top.CreateBucketIfNotExists(name)
+			b.FillPercent = options.FillPercent
 
 			for j := 0; j < options.BatchSize; j++ {
 				var key = make([]byte, options.KeySize)

db.go

@@ -23,15 +23,6 @@ const version = 2
 // Represents a marker value to indicate that a file is a Bolt DB.
 const magic uint32 = 0xED0CDAED
 
-const (
-	minFillPercent = 0.1
-	maxFillPercent = 1.0
-)
-
-// DefaultFillPercent is the percentage that split pages are filled.
-// This value can be changed by setting DB.FillPercent.
-const DefaultFillPercent = 0.5
-
 // DB represents a collection of buckets persisted to a file on disk.
 // All data access is performed through transactions which can be obtained through the DB.
 // All the functions on DB will return a ErrDatabaseNotOpen if accessed before Open() is called.
@@ -42,11 +33,6 @@ type DB struct {
 	// debugging purposes.
 	StrictMode bool
 
-	// Sets the threshold for filling nodes when they split. By default,
-	// the database will fill to 50% but it can be useful to increase this
-	// amount if you know that your write workloads are mostly append-only.
-	FillPercent float64
-
 	// Setting the NoSync flag will cause the database to skip fsync()
 	// calls after each commit. This can be useful when bulk loading data
 	// into a database and you can restart the bulk load in the event of
@@ -99,7 +85,7 @@ func (db *DB) String() string {
 // If the file does not exist then it will be created automatically.
 // Passing in nil options will cause Bolt to open the database with the default options.
 func Open(path string, mode os.FileMode, options *Options) (*DB, error) {
-	var db = &DB{opened: true, FillPercent: DefaultFillPercent}
+	var db = &DB{opened: true}
 
 	// Set default options if no options are provided.
 	if options == nil {

node.go

@@ -255,7 +255,7 @@ func (n *node) splitTwo(pageSize int) (*node, *node) {
 	}
 
 	// Determine the threshold before starting a new node.
-	var fillPercent = n.bucket.tx.db.FillPercent
+	var fillPercent = n.bucket.FillPercent
 	if fillPercent < minFillPercent {
 		fillPercent = minFillPercent
 	} else if fillPercent > maxFillPercent {