Version the leveldb (and keep compatibility with pre-versioned uncompressed databases.

ldb/boundary_test.go

@@ -16,13 +16,16 @@ import (
 func TestEmptyDB(t *testing.T) {
 
 	dbname := "tstdbempty"
+	dbnamever := dbname + ".ver"
 	_ = os.RemoveAll(dbname)
+	_ = os.RemoveAll(dbnamever)
 	db, err := btcdb.CreateDB("leveldb", dbname)
 	if err != nil {
 		t.Errorf("Failed to open test database %v", err)
 		return
 	}
 	defer os.RemoveAll(dbname)
+	defer os.RemoveAll(dbnamever)
 
 	sha, height, err := db.NewestSha()
 	if !sha.IsEqual(&btcwire.ShaHash{}) {

ldb/doc.go

@@ -11,5 +11,12 @@ The performance is generally high although it goes down with database
 size.
 
 Many of the block or tx specific functions for btcdb are in this subpackage.
+
+Database version number is stored in a flat file <dbname>.ver
+Currently a single (littlendian) integer in the file. If there is
+additional data to save in the future, the presense of additional
+data can be indicated by changing the version number, then parsing the
+file differently.
+
 */
 package ldb

ldb/insertremove_test.go

@@ -46,13 +46,16 @@ func TestUnspentInsert(t *testing.T) {
 func testUnspentInsert(t *testing.T, mode int) {
 	// Ignore db remove errors since it means we didn't have an old one.
 	dbname := fmt.Sprintf("tstdbuspnt1.%d", mode)
+	dbnamever := dbname + ".ver"
 	_ = os.RemoveAll(dbname)
+	_ = os.RemoveAll(dbnamever)
 	db, err := btcdb.CreateDB("leveldb", dbname)
 	if err != nil {
 		t.Errorf("Failed to open test database %v", err)
 		return
 	}
 	defer os.RemoveAll(dbname)
+	defer os.RemoveAll(dbnamever)
 	defer db.Close()
 
 	switch mode {

ldb/leveldb.go

@@ -5,6 +5,7 @@
 package ldb
 
 import (
+	"encoding/binary"
 	"fmt"
 	"github.com/conformal/btcdb"
 	"github.com/conformal/btcutil"
@@ -129,9 +130,13 @@ blocknarrow:
 	return db, nil
 }
 
+var CurrentDBVersion int32 = 1
+
 func openDB(dbpath string, flag opt.OptionsFlag) (pbdb btcdb.Db, err error) {
 	var db LevelDb
 	var tlDb *leveldb.DB
+	var dbversion int32
+
 	defer func() {
 		if err == nil {
 			db.lDb = tlDb
@@ -156,14 +161,60 @@ func openDB(dbpath string, flag opt.OptionsFlag) (pbdb btcdb.Db, err error) {
 		}
 	}
 
-	tlDb, err = leveldb.OpenFile(dbpath, &opt.Options{Flag: flag,
+	needVersionFile := false
+	verfile := dbpath + ".ver"
+	fi, ferr := os.Open(verfile)
+	if ferr == nil {
+		defer fi.Close()
+
+		ferr = binary.Read(fi, binary.LittleEndian, &dbversion)
+		if ferr != nil {
+			dbversion = ^0
+		}
+	} else {
+		if flag&opt.OFCreateIfMissing != 0 {
+			needVersionFile = true
+		}
+	}
+
+	opts := &opt.Options{Flag: flag,
 		BlockCache:      cache.EmptyCache{},
 		MaxOpenFiles:    256,
-		CompressionType: opt.NoCompression})
+		CompressionType: opt.NoCompression,
+	}
+
+	switch dbversion {
+	case 0:
+		opts = &opt.Options{Flag: flag}
+	case 1:
+		// uses defaults from above
+	default:
+		err = fmt.Errorf("unsupported db version %v", dbversion)
+		return
+	}
+
+	tlDb, err = leveldb.OpenFile(dbpath, opts)
 	if err != nil {
 		return
 	}
 
+	// If we opened the database successfully on 'create'
+	// update the
+	if needVersionFile {
+		fo, ferr := os.Create(verfile)
+		if ferr != nil {
+			// TODO(design) close and delete database?
+			err = ferr
+			return
+		}
+		defer fo.Close()
+		dbversion = CurrentDBVersion
+		err = binary.Write(fo, binary.LittleEndian, dbversion)
+		if err != nil {
+			return
+		}
+	}
+
 	return
 }
 

ldb/operational_test.go

@@ -42,13 +42,16 @@ func testOperationalMode(t *testing.T, mode int) {
 
 	// Ignore db remove errors since it means we didn't have an old one.
 	dbname := fmt.Sprintf("tstdbop1.%d", mode)
+	dbnamever := dbname + ".ver"
 	_ = os.RemoveAll(dbname)
+	_ = os.RemoveAll(dbnamever)
 	db, err := btcdb.CreateDB("leveldb", dbname)
 	if err != nil {
 		t.Errorf("Failed to open test database %v", err)
 		return
 	}
 	defer os.RemoveAll(dbname)
+	defer os.RemoveAll(dbnamever)
 	defer db.Close()
 
 	switch mode {
@@ -177,13 +180,16 @@ func testBackout(t *testing.T, mode int) {
 	t.Logf("mode %v", mode)
 	// Ignore db remove errors since it means we didn't have an old one.
 	dbname := fmt.Sprintf("tstdbop2.%d", mode)
+	dbnamever := dbname + ".ver"
 	_ = os.RemoveAll(dbname)
+	_ = os.RemoveAll(dbnamever)
 	db, err := btcdb.CreateDB("leveldb", dbname)
 	if err != nil {
 		t.Errorf("Failed to open test database %v", err)
 		return
 	}
 	defer os.RemoveAll(dbname)
+	defer os.RemoveAll(dbnamever)
 	defer db.Close()
 
 	switch mode {