diff --git a/vendor/go.etcd.io/bbolt/bucket.go b/vendor/go.etcd.io/bbolt/bucket.go
new file mode 100644
index 0000000..6371ace
--- /dev/null
+++ b/vendor/go.etcd.io/bbolt/bucket.go
@@ -0,0 +1,1005 @@
+package bbolt
+
+import (
+	"bytes"
+	"fmt"
+	"unsafe"
+
+	"go.etcd.io/bbolt/errors"
+	"go.etcd.io/bbolt/internal/common"
+)
+
+const (
+	// MaxKeySize is the maximum length of a key, in bytes.
+	MaxKeySize = 32768
+
+	// MaxValueSize is the maximum length of a value, in bytes.
+	MaxValueSize = (1 << 31) - 2
+)
+
+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 {
+	*common.InBucket
+	tx       *Tx                   // the associated transaction
+	buckets  map[string]*Bucket    // subbucket cache
+	page     *common.Page          // inline page reference
+	rootNode *node                 // materialized node for the root page.
+	nodes    map[common.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.
+	//
+	// This is non-persisted across transactions so it must be set in every Tx.
+	FillPercent float64
+}
+
+// newBucket returns a new bucket associated with a transaction.
+func newBucket(tx *Tx) Bucket {
+	var b = Bucket{tx: tx, FillPercent: DefaultFillPercent}
+	if tx.writable {
+		b.buckets = make(map[string]*Bucket)
+		b.nodes = make(map[common.Pgid]*node)
+	}
+	return b
+}
+
+// Tx returns the tx of the bucket.
+func (b *Bucket) Tx() *Tx {
+	return b.tx
+}
+
+// Root returns the root of the bucket.
+func (b *Bucket) Root() common.Pgid {
+	return b.RootPage()
+}
+
+// Writable returns whether the bucket is writable.
+func (b *Bucket) Writable() bool {
+	return b.tx.writable
+}
+
+// Cursor creates a cursor associated with the bucket.
+// The cursor is only valid as long as the transaction is open.
+// Do not use a cursor after the transaction is closed.
+func (b *Bucket) Cursor() *Cursor {
+	// Update transaction statistics.
+	b.tx.stats.IncCursorCount(1)
+
+	// Allocate and return a cursor.
+	return &Cursor{
+		bucket: b,
+		stack:  make([]elemRef, 0),
+	}
+}
+
+// Bucket retrieves a nested bucket by name.
+// Returns nil if the bucket does not exist.
+// The bucket instance is only valid for the lifetime of the transaction.
+func (b *Bucket) Bucket(name []byte) *Bucket {
+	if b.buckets != nil {
+		if child := b.buckets[string(name)]; child != nil {
+			return child
+		}
+	}
+
+	// Move cursor to key.
+	c := b.Cursor()
+	k, v, flags := c.seek(name)
+
+	// Return nil if the key doesn't exist or it is not a bucket.
+	if !bytes.Equal(name, k) || (flags&common.BucketLeafFlag) == 0 {
+		return nil
+	}
+
+	// Otherwise create a bucket and cache it.
+	var child = b.openBucket(v)
+	if b.buckets != nil {
+		b.buckets[string(name)] = child
+	}
+
+	return child
+}
+
+// Helper method that re-interprets a sub-bucket value
+// from a parent into a Bucket
+func (b *Bucket) openBucket(value []byte) *Bucket {
+	var child = newBucket(b.tx)
+
+	// Unaligned access requires a copy to be made.
+	const unalignedMask = unsafe.Alignof(struct {
+		common.InBucket
+		common.Page
+	}{}) - 1
+	unaligned := uintptr(unsafe.Pointer(&value[0]))&unalignedMask != 0
+	if unaligned {
+		value = cloneBytes(value)
+	}
+
+	// If this is a writable transaction then we need to copy the bucket entry.
+	// Read-only transactions can point directly at the mmap entry.
+	if b.tx.writable && !unaligned {
+		child.InBucket = &common.InBucket{}
+		*child.InBucket = *(*common.InBucket)(unsafe.Pointer(&value[0]))
+	} else {
+		child.InBucket = (*common.InBucket)(unsafe.Pointer(&value[0]))
+	}
+
+	// Save a reference to the inline page if the bucket is inline.
+	if child.RootPage() == 0 {
+		child.page = (*common.Page)(unsafe.Pointer(&value[common.BucketHeaderSize]))
+	}
+
+	return &child
+}
+
+// CreateBucket creates a new bucket at the given key and returns the new bucket.
+// Returns an error if the key already exists, if the bucket name is blank, or if the bucket name is too long.
+// The bucket instance is only valid for the lifetime of the transaction.
+func (b *Bucket) CreateBucket(key []byte) (rb *Bucket, err error) {
+	if lg := b.tx.db.Logger(); lg != discardLogger {
+		lg.Debugf("Creating bucket %q", key)
+		defer func() {
+			if err != nil {
+				lg.Errorf("Creating bucket %q failed: %v", key, err)
+			} else {
+				lg.Debugf("Creating bucket %q successfully", key)
+			}
+		}()
+	}
+	if b.tx.db == nil {
+		return nil, errors.ErrTxClosed
+	} else if !b.tx.writable {
+		return nil, errors.ErrTxNotWritable
+	} else if len(key) == 0 {
+		return nil, errors.ErrBucketNameRequired
+	}
+
+	// Insert into node.
+	// Tip: Use a new variable `newKey` instead of reusing the existing `key` to prevent
+	// it from being marked as leaking, and accordingly cannot be allocated on stack.
+	newKey := cloneBytes(key)
+
+	// Move cursor to correct position.
+	c := b.Cursor()
+	k, _, flags := c.seek(newKey)
+
+	// Return an error if there is an existing key.
+	if bytes.Equal(newKey, k) {
+		if (flags & common.BucketLeafFlag) != 0 {
+			return nil, errors.ErrBucketExists
+		}
+		return nil, errors.ErrIncompatibleValue
+	}
+
+	// Create empty, inline bucket.
+	var bucket = Bucket{
+		InBucket:    &common.InBucket{},
+		rootNode:    &node{isLeaf: true},
+		FillPercent: DefaultFillPercent,
+	}
+	var value = bucket.write()
+
+	c.node().put(newKey, newKey, value, 0, common.BucketLeafFlag)
+
+	// Since subbuckets are not allowed on inline buckets, we need to
+	// dereference the inline page, if it exists. This will cause the bucket
+	// to be treated as a regular, non-inline bucket for the rest of the tx.
+	b.page = nil
+
+	return b.Bucket(newKey), nil
+}
+
+// CreateBucketIfNotExists creates a new bucket if it doesn't already exist and returns a reference to it.
+// Returns an error if the bucket name is blank, or if the bucket name is too long.
+// The bucket instance is only valid for the lifetime of the transaction.
+func (b *Bucket) CreateBucketIfNotExists(key []byte) (rb *Bucket, err error) {
+	if lg := b.tx.db.Logger(); lg != discardLogger {
+		lg.Debugf("Creating bucket if not exist %q", key)
+		defer func() {
+			if err != nil {
+				lg.Errorf("Creating bucket if not exist %q failed: %v", key, err)
+			} else {
+				lg.Debugf("Creating bucket if not exist %q successfully", key)
+			}
+		}()
+	}
+
+	if b.tx.db == nil {
+		return nil, errors.ErrTxClosed
+	} else if !b.tx.writable {
+		return nil, errors.ErrTxNotWritable
+	} else if len(key) == 0 {
+		return nil, errors.ErrBucketNameRequired
+	}
+
+	// Insert into node.
+	// Tip: Use a new variable `newKey` instead of reusing the existing `key` to prevent
+	// it from being marked as leaking, and accordingly cannot be allocated on stack.
+	newKey := cloneBytes(key)
+
+	if b.buckets != nil {
+		if child := b.buckets[string(newKey)]; child != nil {
+			return child, nil
+		}
+	}
+
+	// Move cursor to correct position.
+	c := b.Cursor()
+	k, v, flags := c.seek(newKey)
+
+	// Return an error if there is an existing non-bucket key.
+	if bytes.Equal(newKey, k) {
+		if (flags & common.BucketLeafFlag) != 0 {
+			var child = b.openBucket(v)
+			if b.buckets != nil {
+				b.buckets[string(newKey)] = child
+			}
+
+			return child, nil
+		}
+		return nil, errors.ErrIncompatibleValue
+	}
+
+	// Create empty, inline bucket.
+	var bucket = Bucket{
+		InBucket:    &common.InBucket{},
+		rootNode:    &node{isLeaf: true},
+		FillPercent: DefaultFillPercent,
+	}
+	var value = bucket.write()
+
+	c.node().put(newKey, newKey, value, 0, common.BucketLeafFlag)
+
+	// Since subbuckets are not allowed on inline buckets, we need to
+	// dereference the inline page, if it exists. This will cause the bucket
+	// to be treated as a regular, non-inline bucket for the rest of the tx.
+	b.page = nil
+
+	return b.Bucket(newKey), nil
+}
+
+// DeleteBucket deletes a bucket at the given key.
+// Returns an error if the bucket does not exist, or if the key represents a non-bucket value.
+func (b *Bucket) DeleteBucket(key []byte) (err error) {
+	if lg := b.tx.db.Logger(); lg != discardLogger {
+		lg.Debugf("Deleting bucket %q", key)
+		defer func() {
+			if err != nil {
+				lg.Errorf("Deleting bucket %q failed: %v", key, err)
+			} else {
+				lg.Debugf("Deleting bucket %q successfully", key)
+			}
+		}()
+	}
+
+	if b.tx.db == nil {
+		return errors.ErrTxClosed
+	} else if !b.Writable() {
+		return errors.ErrTxNotWritable
+	}
+
+	newKey := cloneBytes(key)
+
+	// Move cursor to correct position.
+	c := b.Cursor()
+	k, _, flags := c.seek(newKey)
+
+	// Return an error if bucket doesn't exist or is not a bucket.
+	if !bytes.Equal(newKey, k) {
+		return errors.ErrBucketNotFound
+	} else if (flags & common.BucketLeafFlag) == 0 {
+		return errors.ErrIncompatibleValue
+	}
+
+	// Recursively delete all child buckets.
+	child := b.Bucket(newKey)
+	err = child.ForEachBucket(func(k []byte) error {
+		if err := child.DeleteBucket(k); err != nil {
+			return fmt.Errorf("delete bucket: %s", err)
+		}
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+
+	// Remove cached copy.
+	delete(b.buckets, string(newKey))
+
+	// Release all bucket pages to freelist.
+	child.nodes = nil
+	child.rootNode = nil
+	child.free()
+
+	// Delete the node if we have a matching key.
+	c.node().del(newKey)
+
+	return nil
+}
+
+// MoveBucket moves a sub-bucket from the source bucket to the destination bucket.
+// Returns an error if
+//  1. the sub-bucket cannot be found in the source bucket;
+//  2. or the key already exists in the destination bucket;
+//  3. or the key represents a non-bucket value;
+//  4. the source and destination buckets are the same.
+func (b *Bucket) MoveBucket(key []byte, dstBucket *Bucket) (err error) {
+	lg := b.tx.db.Logger()
+	if lg != discardLogger {
+		lg.Debugf("Moving bucket %q", key)
+		defer func() {
+			if err != nil {
+				lg.Errorf("Moving bucket %q failed: %v", key, err)
+			} else {
+				lg.Debugf("Moving bucket %q successfully", key)
+			}
+		}()
+	}
+
+	if b.tx.db == nil || dstBucket.tx.db == nil {
+		return errors.ErrTxClosed
+	} else if !b.Writable() || !dstBucket.Writable() {
+		return errors.ErrTxNotWritable
+	}
+
+	if b.tx.db.Path() != dstBucket.tx.db.Path() || b.tx != dstBucket.tx {
+		lg.Errorf("The source and target buckets are not in the same db file, source bucket in %s and target bucket in %s", b.tx.db.Path(), dstBucket.tx.db.Path())
+		return errors.ErrDifferentDB
+	}
+
+	newKey := cloneBytes(key)
+
+	// Move cursor to correct position.
+	c := b.Cursor()
+	k, v, flags := c.seek(newKey)
+
+	// Return an error if bucket doesn't exist or is not a bucket.
+	if !bytes.Equal(newKey, k) {
+		return errors.ErrBucketNotFound
+	} else if (flags & common.BucketLeafFlag) == 0 {
+		lg.Errorf("An incompatible key %s exists in the source bucket", newKey)
+		return errors.ErrIncompatibleValue
+	}
+
+	// Do nothing (return true directly) if the source bucket and the
+	// destination bucket are actually the same bucket.
+	if b == dstBucket || (b.RootPage() == dstBucket.RootPage() && b.RootPage() != 0) {
+		lg.Errorf("The source bucket (%s) and the target bucket (%s) are the same bucket", b, dstBucket)
+		return errors.ErrSameBuckets
+	}
+
+	// check whether the key already exists in the destination bucket
+	curDst := dstBucket.Cursor()
+	k, _, flags = curDst.seek(newKey)
+
+	// Return an error if there is an existing key in the destination bucket.
+	if bytes.Equal(newKey, k) {
+		if (flags & common.BucketLeafFlag) != 0 {
+			return errors.ErrBucketExists
+		}
+		lg.Errorf("An incompatible key %s exists in the target bucket", newKey)
+		return errors.ErrIncompatibleValue
+	}
+
+	// remove the sub-bucket from the source bucket
+	delete(b.buckets, string(newKey))
+	c.node().del(newKey)
+
+	// add te sub-bucket to the destination bucket
+	newValue := cloneBytes(v)
+	curDst.node().put(newKey, newKey, newValue, 0, common.BucketLeafFlag)
+
+	return nil
+}
+
+// Inspect returns the structure of the bucket.
+func (b *Bucket) Inspect() BucketStructure {
+	return b.recursivelyInspect([]byte("root"))
+}
+
+func (b *Bucket) recursivelyInspect(name []byte) BucketStructure {
+	bs := BucketStructure{Name: string(name)}
+
+	keyN := 0
+	c := b.Cursor()
+	for k, _, flags := c.first(); k != nil; k, _, flags = c.next() {
+		if flags&common.BucketLeafFlag != 0 {
+			childBucket := b.Bucket(k)
+			childBS := childBucket.recursivelyInspect(k)
+			bs.Children = append(bs.Children, childBS)
+		} else {
+			keyN++
+		}
+	}
+	bs.KeyN = keyN
+
+	return bs
+}
+
+// Get retrieves the value for a key in the bucket.
+// Returns a nil value if the key does not exist or if the key is a nested bucket.
+// The returned value is only valid for the life of the transaction.
+// The returned memory is owned by bbolt and must never be modified; writing to this memory might corrupt the database.
+func (b *Bucket) Get(key []byte) []byte {
+	k, v, flags := b.Cursor().seek(key)
+
+	// Return nil if this is a bucket.
+	if (flags & common.BucketLeafFlag) != 0 {
+		return nil
+	}
+
+	// If our target node isn't the same key as what's passed in then return nil.
+	if !bytes.Equal(key, k) {
+		return nil
+	}
+	return v
+}
+
+// Put sets the value for a key in the bucket.
+// If the key exist then its previous value will be overwritten.
+// Supplied value must remain valid for the life of the transaction.
+// Returns an error if the bucket was created from a read-only transaction, if the key is blank, if the key is too large, or if the value is too large.
+func (b *Bucket) Put(key []byte, value []byte) (err error) {
+	if lg := b.tx.db.Logger(); lg != discardLogger {
+		lg.Debugf("Putting key %q", key)
+		defer func() {
+			if err != nil {
+				lg.Errorf("Putting key %q failed: %v", key, err)
+			} else {
+				lg.Debugf("Putting key %q successfully", key)
+			}
+		}()
+	}
+	if b.tx.db == nil {
+		return errors.ErrTxClosed
+	} else if !b.Writable() {
+		return errors.ErrTxNotWritable
+	} else if len(key) == 0 {
+		return errors.ErrKeyRequired
+	} else if len(key) > MaxKeySize {
+		return errors.ErrKeyTooLarge
+	} else if int64(len(value)) > MaxValueSize {
+		return errors.ErrValueTooLarge
+	}
+
+	// Insert into node.
+	// Tip: Use a new variable `newKey` instead of reusing the existing `key` to prevent
+	// it from being marked as leaking, and accordingly cannot be allocated on stack.
+	newKey := cloneBytes(key)
+
+	// Move cursor to correct position.
+	c := b.Cursor()
+	k, _, flags := c.seek(newKey)
+
+	// Return an error if there is an existing key with a bucket value.
+	if bytes.Equal(newKey, k) && (flags&common.BucketLeafFlag) != 0 {
+		return errors.ErrIncompatibleValue
+	}
+
+	// gofail: var beforeBucketPut struct{}
+
+	c.node().put(newKey, newKey, value, 0, 0)
+
+	return nil
+}
+
+// Delete removes a key from the bucket.
+// If the key does not exist then nothing is done and a nil error is returned.
+// Returns an error if the bucket was created from a read-only transaction.
+func (b *Bucket) Delete(key []byte) (err error) {
+	if lg := b.tx.db.Logger(); lg != discardLogger {
+		lg.Debugf("Deleting key %q", key)
+		defer func() {
+			if err != nil {
+				lg.Errorf("Deleting key %q failed: %v", key, err)
+			} else {
+				lg.Debugf("Deleting key %q successfully", key)
+			}
+		}()
+	}
+
+	if b.tx.db == nil {
+		return errors.ErrTxClosed
+	} else if !b.Writable() {
+		return errors.ErrTxNotWritable
+	}
+
+	// Move cursor to correct position.
+	c := b.Cursor()
+	k, _, flags := c.seek(key)
+
+	// Return nil if the key doesn't exist.
+	if !bytes.Equal(key, k) {
+		return nil
+	}
+
+	// Return an error if there is already existing bucket value.
+	if (flags & common.BucketLeafFlag) != 0 {
+		return errors.ErrIncompatibleValue
+	}
+
+	// Delete the node if we have a matching key.
+	c.node().del(key)
+
+	return nil
+}
+
+// Sequence returns the current integer for the bucket without incrementing it.
+func (b *Bucket) Sequence() uint64 {
+	return b.InSequence()
+}
+
+// SetSequence updates the sequence number for the bucket.
+func (b *Bucket) SetSequence(v uint64) error {
+	if b.tx.db == nil {
+		return errors.ErrTxClosed
+	} else if !b.Writable() {
+		return errors.ErrTxNotWritable
+	}
+
+	// Materialize the root node if it hasn't been already so that the
+	// bucket will be saved during commit.
+	if b.rootNode == nil {
+		_ = b.node(b.RootPage(), nil)
+	}
+
+	// Set the sequence.
+	b.SetInSequence(v)
+	return nil
+}
+
+// NextSequence returns an autoincrementing integer for the bucket.
+func (b *Bucket) NextSequence() (uint64, error) {
+	if b.tx.db == nil {
+		return 0, errors.ErrTxClosed
+	} else if !b.Writable() {
+		return 0, errors.ErrTxNotWritable
+	}
+
+	// Materialize the root node if it hasn't been already so that the
+	// bucket will be saved during commit.
+	if b.rootNode == nil {
+		_ = b.node(b.RootPage(), nil)
+	}
+
+	// Increment and return the sequence.
+	b.IncSequence()
+	return b.Sequence(), nil
+}
+
+// ForEach executes a function for each key/value pair in a bucket.
+// Because ForEach uses a Cursor, the iteration over keys is in lexicographical order.
+// If the provided function returns an error then the iteration is stopped and
+// the error is returned to the caller. The provided function must not modify
+// the bucket; this will result in undefined behavior.
+func (b *Bucket) ForEach(fn func(k, v []byte) error) error {
+	if b.tx.db == nil {
+		return errors.ErrTxClosed
+	}
+	c := b.Cursor()
+	for k, v := c.First(); k != nil; k, v = c.Next() {
+		if err := fn(k, v); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (b *Bucket) ForEachBucket(fn func(k []byte) error) error {
+	if b.tx.db == nil {
+		return errors.ErrTxClosed
+	}
+	c := b.Cursor()
+	for k, _, flags := c.first(); k != nil; k, _, flags = c.next() {
+		if flags&common.BucketLeafFlag != 0 {
+			if err := fn(k); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+// Stats returns stats on a bucket.
+func (b *Bucket) Stats() BucketStats {
+	var s, subStats BucketStats
+	pageSize := b.tx.db.pageSize
+	s.BucketN += 1
+	if b.RootPage() == 0 {
+		s.InlineBucketN += 1
+	}
+	b.forEachPage(func(p *common.Page, depth int, pgstack []common.Pgid) {
+		if p.IsLeafPage() {
+			s.KeyN += int(p.Count())
+
+			// used totals the used bytes for the page
+			used := common.PageHeaderSize
+
+			if p.Count() != 0 {
+				// If page has any elements, add all element headers.
+				used += common.LeafPageElementSize * uintptr(p.Count()-1)
+
+				// Add all element key, value sizes.
+				// The computation takes advantage of the fact that the position
+				// of the last element's key/value equals to the total of the sizes
+				// of all previous elements' keys and values.
+				// It also includes the last element's header.
+				lastElement := p.LeafPageElement(p.Count() - 1)
+				used += uintptr(lastElement.Pos() + lastElement.Ksize() + lastElement.Vsize())
+			}
+
+			if b.RootPage() == 0 {
+				// For inlined bucket just update the inline stats
+				s.InlineBucketInuse += int(used)
+			} else {
+				// For non-inlined bucket update all the leaf stats
+				s.LeafPageN++
+				s.LeafInuse += int(used)
+				s.LeafOverflowN += int(p.Overflow())
+
+				// Collect stats from sub-buckets.
+				// Do that by iterating over all element headers
+				// looking for the ones with the bucketLeafFlag.
+				for i := uint16(0); i < p.Count(); i++ {
+					e := p.LeafPageElement(i)
+					if (e.Flags() & common.BucketLeafFlag) != 0 {
+						// For any bucket element, open the element value
+						// and recursively call Stats on the contained bucket.
+						subStats.Add(b.openBucket(e.Value()).Stats())
+					}
+				}
+			}
+		} else if p.IsBranchPage() {
+			s.BranchPageN++
+			lastElement := p.BranchPageElement(p.Count() - 1)
+
+			// used totals the used bytes for the page
+			// Add header and all element headers.
+			used := common.PageHeaderSize + (common.BranchPageElementSize * uintptr(p.Count()-1))
+
+			// Add size of all keys and values.
+			// Again, use the fact that last element's position equals to
+			// the total of key, value sizes of all previous elements.
+			used += uintptr(lastElement.Pos() + lastElement.Ksize())
+			s.BranchInuse += int(used)
+			s.BranchOverflowN += int(p.Overflow())
+		}
+
+		// Keep track of maximum page depth.
+		if depth+1 > s.Depth {
+			s.Depth = depth + 1
+		}
+	})
+
+	// Alloc stats can be computed from page counts and pageSize.
+	s.BranchAlloc = (s.BranchPageN + s.BranchOverflowN) * pageSize
+	s.LeafAlloc = (s.LeafPageN + s.LeafOverflowN) * pageSize
+
+	// Add the max depth of sub-buckets to get total nested depth.
+	s.Depth += subStats.Depth
+	// Add the stats for all sub-buckets
+	s.Add(subStats)
+	return s
+}
+
+// forEachPage iterates over every page in a bucket, including inline pages.
+func (b *Bucket) forEachPage(fn func(*common.Page, int, []common.Pgid)) {
+	// If we have an inline page then just use that.
+	if b.page != nil {
+		fn(b.page, 0, []common.Pgid{b.RootPage()})
+		return
+	}
+
+	// Otherwise traverse the page hierarchy.
+	b.tx.forEachPage(b.RootPage(), fn)
+}
+
+// forEachPageNode iterates over every page (or node) in a bucket.
+// This also includes inline pages.
+func (b *Bucket) forEachPageNode(fn func(*common.Page, *node, int)) {
+	// If we have an inline page or root node then just use that.
+	if b.page != nil {
+		fn(b.page, nil, 0)
+		return
+	}
+	b._forEachPageNode(b.RootPage(), 0, fn)
+}
+
+func (b *Bucket) _forEachPageNode(pgId common.Pgid, depth int, fn func(*common.Page, *node, int)) {
+	var p, n = b.pageNode(pgId)
+
+	// Execute function.
+	fn(p, n, depth)
+
+	// Recursively loop over children.
+	if p != nil {
+		if p.IsBranchPage() {
+			for i := 0; i < int(p.Count()); i++ {
+				elem := p.BranchPageElement(uint16(i))
+				b._forEachPageNode(elem.Pgid(), depth+1, fn)
+			}
+		}
+	} else {
+		if !n.isLeaf {
+			for _, inode := range n.inodes {
+				b._forEachPageNode(inode.Pgid(), depth+1, fn)
+			}
+		}
+	}
+}
+
+// spill writes all the nodes for this bucket to dirty pages.
+func (b *Bucket) spill() error {
+	// Spill all child buckets first.
+	for name, child := range b.buckets {
+		// If the child bucket is small enough and it has no child buckets then
+		// write it inline into the parent bucket's page. Otherwise spill it
+		// like a normal bucket and make the parent value a pointer to the page.
+		var value []byte
+		if child.inlineable() {
+			child.free()
+			value = child.write()
+		} else {
+			if err := child.spill(); err != nil {
+				return err
+			}
+
+			// Update the child bucket header in this bucket.
+			value = make([]byte, unsafe.Sizeof(common.InBucket{}))
+			var bucket = (*common.InBucket)(unsafe.Pointer(&value[0]))
+			*bucket = *child.InBucket
+		}
+
+		// Skip writing the bucket if there are no materialized nodes.
+		if child.rootNode == nil {
+			continue
+		}
+
+		// Update parent node.
+		var c = b.Cursor()
+		k, _, flags := c.seek([]byte(name))
+		if !bytes.Equal([]byte(name), k) {
+			panic(fmt.Sprintf("misplaced bucket header: %x -> %x", []byte(name), k))
+		}
+		if flags&common.BucketLeafFlag == 0 {
+			panic(fmt.Sprintf("unexpected bucket header flag: %x", flags))
+		}
+		c.node().put([]byte(name), []byte(name), value, 0, common.BucketLeafFlag)
+	}
+
+	// Ignore if there's not a materialized root node.
+	if b.rootNode == nil {
+		return nil
+	}
+
+	// Spill nodes.
+	if err := b.rootNode.spill(); err != nil {
+		return err
+	}
+	b.rootNode = b.rootNode.root()
+
+	// Update the root node for this bucket.
+	if b.rootNode.pgid >= b.tx.meta.Pgid() {
+		panic(fmt.Sprintf("pgid (%d) above high water mark (%d)", b.rootNode.pgid, b.tx.meta.Pgid()))
+	}
+	b.SetRootPage(b.rootNode.pgid)
+
+	return nil
+}
+
+// inlineable returns true if a bucket is small enough to be written inline
+// and if it contains no subbuckets. Otherwise, returns false.
+func (b *Bucket) inlineable() bool {
+	var n = b.rootNode
+
+	// Bucket must only contain a single leaf node.
+	if n == nil || !n.isLeaf {
+		return false
+	}
+
+	// Bucket is not inlineable if it contains subbuckets or if it goes beyond
+	// our threshold for inline bucket size.
+	var size = common.PageHeaderSize
+	for _, inode := range n.inodes {
+		size += common.LeafPageElementSize + uintptr(len(inode.Key())) + uintptr(len(inode.Value()))
+
+		if inode.Flags()&common.BucketLeafFlag != 0 {
+			return false
+		} else if size > b.maxInlineBucketSize() {
+			return false
+		}
+	}
+
+	return true
+}
+
+// Returns the maximum total size of a bucket to make it a candidate for inlining.
+func (b *Bucket) maxInlineBucketSize() uintptr {
+	return uintptr(b.tx.db.pageSize / 4)
+}
+
+// write allocates and writes a bucket to a byte slice.
+func (b *Bucket) write() []byte {
+	// Allocate the appropriate size.
+	var n = b.rootNode
+	var value = make([]byte, common.BucketHeaderSize+n.size())
+
+	// Write a bucket header.
+	var bucket = (*common.InBucket)(unsafe.Pointer(&value[0]))
+	*bucket = *b.InBucket
+
+	// Convert byte slice to a fake page and write the root node.
+	var p = (*common.Page)(unsafe.Pointer(&value[common.BucketHeaderSize]))
+	n.write(p)
+
+	return value
+}
+
+// rebalance attempts to balance all nodes.
+func (b *Bucket) rebalance() {
+	for _, n := range b.nodes {
+		n.rebalance()
+	}
+	for _, child := range b.buckets {
+		child.rebalance()
+	}
+}
+
+// node creates a node from a page and associates it with a given parent.
+func (b *Bucket) node(pgId common.Pgid, parent *node) *node {
+	common.Assert(b.nodes != nil, "nodes map expected")
+
+	// Retrieve node if it's already been created.
+	if n := b.nodes[pgId]; n != nil {
+		return n
+	}
+
+	// Otherwise create a node and cache it.
+	n := &node{bucket: b, parent: parent}
+	if parent == nil {
+		b.rootNode = n
+	} else {
+		parent.children = append(parent.children, n)
+	}
+
+	// Use the inline page if this is an inline bucket.
+	var p = b.page
+	if p == nil {
+		p = b.tx.page(pgId)
+	} else {
+		// if p isn't nil, then it's an inline bucket.
+		// The pgId must be 0 in this case.
+		common.Verify(func() {
+			common.Assert(pgId == 0, "The page ID (%d) isn't 0 for an inline bucket", pgId)
+		})
+	}
+
+	// Read the page into the node and cache it.
+	n.read(p)
+	b.nodes[pgId] = n
+
+	// Update statistics.
+	b.tx.stats.IncNodeCount(1)
+
+	return n
+}
+
+// free recursively frees all pages in the bucket.
+func (b *Bucket) free() {
+	if b.RootPage() == 0 {
+		return
+	}
+
+	var tx = b.tx
+	b.forEachPageNode(func(p *common.Page, n *node, _ int) {
+		if p != nil {
+			tx.db.freelist.Free(tx.meta.Txid(), p)
+		} else {
+			n.free()
+		}
+	})
+	b.SetRootPage(0)
+}
+
+// dereference removes all references to the old mmap.
+func (b *Bucket) dereference() {
+	if b.rootNode != nil {
+		b.rootNode.root().dereference()
+	}
+
+	for _, child := range b.buckets {
+		child.dereference()
+	}
+}
+
+// pageNode returns the in-memory node, if it exists.
+// Otherwise, returns the underlying page.
+func (b *Bucket) pageNode(id common.Pgid) (*common.Page, *node) {
+	// Inline buckets have a fake page embedded in their value so treat them
+	// differently. We'll return the rootNode (if available) or the fake page.
+	if b.RootPage() == 0 {
+		if id != 0 {
+			panic(fmt.Sprintf("inline bucket non-zero page access(2): %d != 0", id))
+		}
+		if b.rootNode != nil {
+			return nil, b.rootNode
+		}
+		return b.page, nil
+	}
+
+	// Check the node cache for non-inline buckets.
+	if b.nodes != nil {
+		if n := b.nodes[id]; n != nil {
+			return nil, n
+		}
+	}
+
+	// Finally lookup the page from the transaction if no node is materialized.
+	return b.tx.page(id), nil
+}
+
+// BucketStats records statistics about resources used by a bucket.
+type BucketStats struct {
+	// Page count statistics.
+	BranchPageN     int // number of logical branch pages
+	BranchOverflowN int // number of physical branch overflow pages
+	LeafPageN       int // number of logical leaf pages
+	LeafOverflowN   int // number of physical leaf overflow pages
+
+	// Tree statistics.
+	KeyN  int // number of keys/value pairs
+	Depth int // number of levels in B+tree
+
+	// Page size utilization.
+	BranchAlloc int // bytes allocated for physical branch pages
+	BranchInuse int // bytes actually used for branch data
+	LeafAlloc   int // bytes allocated for physical leaf pages
+	LeafInuse   int // bytes actually used for leaf data
+
+	// Bucket statistics
+	BucketN           int // total number of buckets including the top bucket
+	InlineBucketN     int // total number on inlined buckets
+	InlineBucketInuse int // bytes used for inlined buckets (also accounted for in LeafInuse)
+}
+
+func (s *BucketStats) Add(other BucketStats) {
+	s.BranchPageN += other.BranchPageN
+	s.BranchOverflowN += other.BranchOverflowN
+	s.LeafPageN += other.LeafPageN
+	s.LeafOverflowN += other.LeafOverflowN
+	s.KeyN += other.KeyN
+	if s.Depth < other.Depth {
+		s.Depth = other.Depth
+	}
+	s.BranchAlloc += other.BranchAlloc
+	s.BranchInuse += other.BranchInuse
+	s.LeafAlloc += other.LeafAlloc
+	s.LeafInuse += other.LeafInuse
+
+	s.BucketN += other.BucketN
+	s.InlineBucketN += other.InlineBucketN
+	s.InlineBucketInuse += other.InlineBucketInuse
+}
+
+// cloneBytes returns a copy of a given slice.
+func cloneBytes(v []byte) []byte {
+	var clone = make([]byte, len(v))
+	copy(clone, v)
+	return clone
+}
+
+type BucketStructure struct {
+	Name     string            `json:"name"`              // name of the bucket
+	KeyN     int               `json:"keyN"`              // number of key/value pairs
+	Children []BucketStructure `json:"buckets,omitempty"` // child buckets
+}