Add 'bolt pages'.

cmd/bolt/main.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"log"
 	"os"
+	"strconv"
 
 	"github.com/boltdb/bolt"
 	"github.com/codegangsta/cli"
@@ -30,6 +31,11 @@ func NewApp() *cli.App {
 			Usage:  "retrieve a list of all keys in a bucket",
 			Action: KeysCommand,
 		},
+		{
+			Name:   "pages",
+			Usage:  "dump page information for a database",
+			Action: PagesCommand,
+		},
 	}
 	return app
 }
@@ -108,6 +114,45 @@ func KeysCommand(c *cli.Context) {
 	}
 }
 
+// PagesCommand prints a list of all pages in a database.
+func PagesCommand(c *cli.Context) {
+	path := c.Args().Get(0)
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		fatal(err)
+		return
+	}
+
+	db, err := bolt.Open(path, 0600)
+	if err != nil {
+		fatal(err)
+		return
+	}
+	defer db.Close()
+
+	logger.Println("ID       TYPE       ITEMS  OVRFLW")
+	logger.Println("======== ========== ====== ======")
+
+	db.Do(func(tx *bolt.Tx) error {
+		var id int
+		for {
+			p, err := tx.Page(id)
+			if err != nil {
+				fatalf("page error: %d: %s", id, err)
+			} else if p == nil {
+				break
+			}
+
+			var overflow string
+			if p.OverflowCount > 0 {
+				overflow = strconv.Itoa(p.OverflowCount)
+			}
+			logger.Printf("%-8d %-10s %-6d %-6s", p.ID, p.Type, p.Count, overflow)
+			id += 1 + p.OverflowCount
+		}
+		return nil
+	})
+}
+
 var logger = log.New(os.Stderr, "", 0)
 var logBuffer *bytes.Buffer
 

freelist.go

@@ -70,6 +70,23 @@ func (f *freelist) release(txid txid) {
 	sort.Sort(reverseSortedPgids(f.ids))
 }
 
+// isFree returns whether a given page is in the free list.
+func (f *freelist) isFree(pgid pgid) bool {
+	for _, id := range f.ids {
+		if id == pgid {
+			return true
+		}
+	}
+	for _, m := range f.pending {
+		for _, id := range m {
+			if id == pgid {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 // read initializes the freelist from a freelist page.
 func (f *freelist) read(p *page) {
 	ids := ((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[0:p.count]

page.go

@@ -119,3 +119,11 @@ func (n *leafPageElement) value() []byte {
 	buf := (*[maxAllocSize]byte)(unsafe.Pointer(n))
 	return buf[n.pos+n.ksize : n.pos+n.ksize+n.vsize]
 }
+
+// PageInfo represents human readable information about a page.
+type PageInfo struct {
+	ID            int
+	Type          string
+	Count         int
+	OverflowCount int
+}

tx.go

@@ -420,3 +420,30 @@ func (t *Tx) forEachPage(pgid pgid, depth int, fn func(*page, int)) {
 		}
 	}
 }
+
+// Page returns page information for a given page number.
+// This is only available from writable transactions.
+func (t *Tx) Page(id int) (*PageInfo, error) {
+	if !t.writable {
+		return nil, ErrTxNotWritable
+	} else if pgid(id) >= t.meta.pgid {
+		return nil, nil
+	}
+
+	// Build the page info.
+	p := t.page(pgid(id))
+	info := &PageInfo{
+		ID:            id,
+		Count:         int(p.count),
+		OverflowCount: int(p.overflow),
+	}
+
+	// Determine the type (or if it's free).
+	if t.db.freelist.isFree(pgid(id)) {
+		info.Type = "free"
+	} else {
+		info.Type = p.typ()
+	}
+
+	return info, nil
+}