leveldb: change the table file extension from .sst to .ldb, as per

the C++ leveldb project.

https://groups.google.com/forum/#!topic/leveldb/u9izbG-pDis

R=bradfitz, adg
CC=golang-dev
https://codereview.appspot.com/20170043

leveldb/compaction_test.go

@@ -644,7 +644,7 @@ func TestCompaction(t *testing.T) {
 			t.Errorf("%q: mem: got %q, want %q", tc.key, gotMem, tc.wantMem)
 		}
 		if gotDisk != tc.wantDisk {
-			t.Errorf("%q: sst: got %q, want %q", tc.key, gotDisk, tc.wantDisk)
+			t.Errorf("%q: ldb: got %q, want %q", tc.key, gotDisk, tc.wantDisk)
 		}
 	}
 

leveldb/filenames.go

@@ -20,6 +20,7 @@ const (
 	fileTypeLog fileType = iota
 	fileTypeLock
 	fileTypeTable
+	fileTypeOldFashionedTable
 	fileTypeManifest
 	fileTypeCurrent
 )
@@ -34,6 +35,8 @@ func dbFilename(dirname string, fileType fileType, fileNum uint64) string {
 	case fileTypeLock:
 		return fmt.Sprintf("%s%cLOCK", dirname, os.PathSeparator)
 	case fileTypeTable:
+		return fmt.Sprintf("%s%c%06d.ldb", dirname, os.PathSeparator, fileNum)
+	case fileTypeOldFashionedTable:
 		return fmt.Sprintf("%s%c%06d.sst", dirname, os.PathSeparator, fileNum)
 	case fileTypeManifest:
 		return fmt.Sprintf("%s%cMANIFEST-%06d", dirname, os.PathSeparator, fileNum)
@@ -66,10 +69,12 @@ func parseDBFilename(filename string) (fileType fileType, fileNum uint64, ok boo
 			break
 		}
 		switch filename[i+1:] {
+		case "ldb":
+			return fileTypeTable, u, true
 		case "log":
 			return fileTypeLog, u, true
 		case "sst":
-			return fileTypeTable, u, true
+			return fileTypeOldFashionedTable, u, true
 		}
 	}
 	return 0, 0, false

leveldb/filenames_test.go

@@ -16,7 +16,9 @@ func TestParseDBFilename(t *testing.T) {
 		"000000..log":         false,
 		"a000000.log":         false,
 		"abcdef.log":          false,
-		"000001.sst":          true,
+		"000001ldb":           false,
+		"000001.ldb":          true,
+		"000002.sst":          true,
 		"CURRENT":             true,
 		"CURRaNT":             false,
 		"LOCK":                true,
@@ -42,9 +44,10 @@ func TestFilenameRoundTrip(t *testing.T) {
 		fileTypeCurrent: false,
 		fileTypeLock:    false,
 		// The remaining file types are numbered.
-		fileTypeLog:      true,
-		fileTypeManifest: true,
-		fileTypeTable:    true,
+		fileTypeLog:               true,
+		fileTypeManifest:          true,
+		fileTypeOldFashionedTable: true,
+		fileTypeTable:             true,
 	}
 	for fileType, numbered := range testCases {
 		fileNums := []uint64{0}

leveldb/leveldb.go

@@ -637,7 +637,7 @@ func (d *DB) deleteObsoleteFiles() {
 			keep = fileNum >= logNumber
 		case fileTypeManifest:
 			keep = fileNum >= manifestFileNumber
-		case fileTypeTable:
+		case fileTypeTable, fileTypeOldFashionedTable:
 			_, keep = liveFileNums[fileNum]
 		}
 		if keep {

leveldb/table_cache.go

@@ -5,6 +5,7 @@
 package leveldb
 
 import (
+	"os"
 	"sync"
 
 	"code.google.com/p/leveldb-go/leveldb/db"
@@ -148,7 +149,12 @@ type tableCacheNode struct {
 }
 
 func (n *tableCacheNode) load(c *tableCache) {
+	// Try opening the fileTypeTable first. If that file doesn't exist,
+	// fall back onto the fileTypeOldFashionedTable.
 	f, err := c.fs.Open(dbFilename(c.dirname, fileTypeTable, n.fileNum))
+	if os.IsNotExist(err) {
+		f, err = c.fs.Open(dbFilename(c.dirname, fileTypeOldFashionedTable, n.fileNum))
+	}
 	if err != nil {
 		n.result <- tableReaderOrError{err: err}
 		return