lib/mergeset: consistently use OS-independent separator in file paths

This is needed for Windows support, which uses `\` instead of `/` as file separator

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/70

lib/mergeset/block_stream_reader.go

@@ -147,7 +147,7 @@ func (bsr *blockStreamReader) InitFromFilePart(path string) error {
 		return fmt.Errorf("cannot read metadata from %q: %w", path, err)
 	}
 
-	metaindexPath := path + "/metaindex.bin"
+	metaindexPath := filepath.Join(path, metaindexFilename)
 	metaindexFile, err := filestream.Open(metaindexPath, true)
 	if err != nil {
 		return fmt.Errorf("cannot open metaindex file in stream mode: %w", err)
@@ -158,20 +158,20 @@ func (bsr *blockStreamReader) InitFromFilePart(path string) error {
 		return fmt.Errorf("cannot unmarshal metaindex rows from file %q: %w", metaindexPath, err)
 	}
 
-	indexPath := path + "/index.bin"
+	indexPath := filepath.Join(path, indexFilename)
 	indexFile, err := filestream.Open(indexPath, true)
 	if err != nil {
 		return fmt.Errorf("cannot open index file in stream mode: %w", err)
 	}
 
-	itemsPath := path + "/items.bin"
+	itemsPath := filepath.Join(path, itemsFilename)
 	itemsFile, err := filestream.Open(itemsPath, true)
 	if err != nil {
 		indexFile.MustClose()
 		return fmt.Errorf("cannot open items file in stream mode: %w", err)
 	}
 
-	lensPath := path + "/lens.bin"
+	lensPath := filepath.Join(path, lensFilename)
 	lensFile, err := filestream.Open(lensPath, true)
 	if err != nil {
 		indexFile.MustClose()

lib/mergeset/block_stream_writer.go

@@ -88,14 +88,14 @@ func (bsw *blockStreamWriter) InitFromFilePart(path string, nocache bool, compre
 
 	// Always cache metaindex file in OS page cache, since it is immediately
 	// read after the merge.
-	metaindexPath := path + "/metaindex.bin"
+	metaindexPath := filepath.Join(path, metaindexFilename)
 	metaindexFile, err := filestream.Create(metaindexPath, false)
 	if err != nil {
 		fs.MustRemoveDirAtomic(path)
 		return fmt.Errorf("cannot create metaindex file: %w", err)
 	}
 
-	indexPath := path + "/index.bin"
+	indexPath := filepath.Join(path, indexFilename)
 	indexFile, err := filestream.Create(indexPath, nocache)
 	if err != nil {
 		metaindexFile.MustClose()
@@ -103,7 +103,7 @@ func (bsw *blockStreamWriter) InitFromFilePart(path string, nocache bool, compre
 		return fmt.Errorf("cannot create index file: %w", err)
 	}
 
-	itemsPath := path + "/items.bin"
+	itemsPath := filepath.Join(path, itemsFilename)
 	itemsFile, err := filestream.Create(itemsPath, nocache)
 	if err != nil {
 		metaindexFile.MustClose()
@@ -112,7 +112,7 @@ func (bsw *blockStreamWriter) InitFromFilePart(path string, nocache bool, compre
 		return fmt.Errorf("cannot create items file: %w", err)
 	}
 
-	lensPath := path + "/lens.bin"
+	lensPath := filepath.Join(path, lensFilename)
 	lensFile, err := filestream.Create(lensPath, nocache)
 	if err != nil {
 		metaindexFile.MustClose()

lib/mergeset/filenames.go

@@ -0,0 +1,10 @@
+package mergeset
+
+const (
+	metaindexFilename = "metaindex.bin"
+	indexFilename     = "index.bin"
+	itemsFilename     = "items.bin"
+	lensFilename      = "lens.bin"
+	metadataFilename  = "metadata.json"
+	partsFilename     = "parts.json"
+)

lib/mergeset/inmemory_part.go

@@ -37,19 +37,19 @@ func (mp *inmemoryPart) StoreToDisk(path string) error {
 	if err := fs.MkdirAllIfNotExist(path); err != nil {
 		return fmt.Errorf("cannot create directory %q: %w", path, err)
 	}
-	metaindexPath := path + "/metaindex.bin"
+	metaindexPath := filepath.Join(path, metaindexFilename)
 	if err := fs.WriteFileAndSync(metaindexPath, mp.metaindexData.B); err != nil {
 		return fmt.Errorf("cannot store metaindex: %w", err)
 	}
-	indexPath := path + "/index.bin"
+	indexPath := filepath.Join(path, indexFilename)
 	if err := fs.WriteFileAndSync(indexPath, mp.indexData.B); err != nil {
 		return fmt.Errorf("cannot store index: %w", err)
 	}
-	itemsPath := path + "/items.bin"
+	itemsPath := filepath.Join(path, itemsFilename)
 	if err := fs.WriteFileAndSync(itemsPath, mp.itemsData.B); err != nil {
 		return fmt.Errorf("cannot store items: %w", err)
 	}
-	lensPath := path + "/lens.bin"
+	lensPath := filepath.Join(path, lensFilename)
 	if err := fs.WriteFileAndSync(lensPath, mp.lensData.B); err != nil {
 		return fmt.Errorf("cannot store lens: %w", err)
 	}

lib/mergeset/part.go

@@ -2,6 +2,7 @@ package mergeset
 
 import (
 	"fmt"
+	"path/filepath"
 	"sync"
 	"unsafe"
 
@@ -72,22 +73,22 @@ func openFilePart(path string) (*part, error) {
 		return nil, fmt.Errorf("cannot read part metadata: %w", err)
 	}
 
-	metaindexPath := path + "/metaindex.bin"
+	metaindexPath := filepath.Join(path, metaindexFilename)
 	metaindexFile, err := filestream.Open(metaindexPath, true)
 	if err != nil {
 		return nil, fmt.Errorf("cannot open %q: %w", metaindexPath, err)
 	}
 	metaindexSize := fs.MustFileSize(metaindexPath)
 
-	indexPath := path + "/index.bin"
+	indexPath := filepath.Join(path, indexFilename)
 	indexFile := fs.MustOpenReaderAt(indexPath)
 	indexSize := fs.MustFileSize(indexPath)
 
-	itemsPath := path + "/items.bin"
+	itemsPath := filepath.Join(path, itemsFilename)
 	itemsFile := fs.MustOpenReaderAt(itemsPath)
 	itemsSize := fs.MustFileSize(itemsPath)
 
-	lensPath := path + "/lens.bin"
+	lensPath := filepath.Join(path, lensFilename)
 	lensFile := fs.MustOpenReaderAt(lensPath)
 	lensSize := fs.MustFileSize(lensPath)
 

lib/mergeset/part_header.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"path/filepath"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fs"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
@@ -81,7 +82,7 @@ func (ph *partHeader) ReadMetadata(partPath string) error {
 	ph.Reset()
 
 	// Read ph fields from metadata.
-	metadataPath := partPath + "/metadata.json"
+	metadataPath := filepath.Join(partPath, metadataFilename)
 	metadata, err := os.ReadFile(metadataPath)
 	if err != nil {
 		return fmt.Errorf("cannot read %q: %w", metadataPath, err)
@@ -123,7 +124,7 @@ func (ph *partHeader) WriteMetadata(partPath string) error {
 	if err != nil {
 		logger.Panicf("BUG: cannot marshal partHeader metadata: %s", err)
 	}
-	metadataPath := partPath + "/metadata.json"
+	metadataPath := filepath.Join(partPath, metadataFilename)
 	if err := fs.WriteFileAtomically(metadataPath, metadata, false); err != nil {
 		return fmt.Errorf("cannot create %q: %w", metadataPath, err)
 	}

lib/mergeset/table.go

@@ -1085,7 +1085,7 @@ func (tb *Table) mergeParts(pws []*partWrapper, stopCh <-chan struct{}, isFinal
 	mergeIdx := tb.nextMergeIdx()
 	dstPartPath := ""
 	if dstPartType == partFile {
-		dstPartPath = fmt.Sprintf("%s/%016X", tb.path, mergeIdx)
+		dstPartPath = filepath.Join(tb.path, fmt.Sprintf("%016X", mergeIdx))
 	}
 
 	if isFinal && len(pws) == 1 && pws[0].mp != nil {
@@ -1379,8 +1379,8 @@ func openParts(path string) ([]*partWrapper, error) {
 
 	// Remove txn and tmp directories, which may be left after the upgrade
 	// to v1.90.0 and newer versions.
-	fs.MustRemoveAll(path + "/txn")
-	fs.MustRemoveAll(path + "/tmp")
+	fs.MustRemoveAll(filepath.Join(path, "txn"))
+	fs.MustRemoveAll(filepath.Join(path, "tmp"))
 
 	partNames := mustReadPartNames(path)
 
@@ -1401,7 +1401,7 @@ func openParts(path string) ([]*partWrapper, error) {
 		}
 		fn := de.Name()
 		if _, ok := m[fn]; !ok {
-			deletePath := path + "/" + fn
+			deletePath := filepath.Join(path, fn)
 			fs.MustRemoveAll(deletePath)
 		}
 	}
@@ -1410,7 +1410,7 @@ func openParts(path string) ([]*partWrapper, error) {
 	// Open parts
 	var pws []*partWrapper
 	for _, partName := range partNames {
-		partPath := path + "/" + partName
+		partPath := filepath.Join(path, partName)
 		p, err := openFilePart(partPath)
 		if err != nil {
 			mustCloseParts(pws)
@@ -1456,7 +1456,7 @@ func (tb *Table) CreateSnapshotAt(dstDir string, deadline uint64) error {
 	if err != nil {
 		return fmt.Errorf("cannot obtain absolute dir for %q: %w", dstDir, err)
 	}
-	if strings.HasPrefix(dstDir, srcDir+"/") {
+	if strings.HasPrefix(dstDir, srcDir+string(filepath.Separator)) {
 		return fmt.Errorf("cannot create snapshot %q inside the data dir %q", dstDir, srcDir)
 	}
 
@@ -1483,7 +1483,7 @@ func (tb *Table) CreateSnapshotAt(dstDir string, deadline uint64) error {
 			return fmt.Errorf("cannot create snapshot for %q: timeout exceeded", tb.path)
 		}
 		srcPartPath := pw.p.path
-		dstPartPath := dstDir + "/" + filepath.Base(srcPartPath)
+		dstPartPath := filepath.Join(dstDir, filepath.Base(srcPartPath))
 		if err := fs.HardLinkFiles(srcPartPath, dstPartPath); err != nil {
 			return fmt.Errorf("cannot create hard links from %q to %q: %w", srcPartPath, dstPartPath, err)
 		}
@@ -1512,14 +1512,14 @@ func mustWritePartNames(pws []*partWrapper, dstDir string) {
 	if err != nil {
 		logger.Panicf("BUG: cannot marshal partNames to JSON: %s", err)
 	}
-	partNamesPath := dstDir + "/parts.json"
+	partNamesPath := filepath.Join(dstDir, partsFilename)
 	if err := fs.WriteFileAtomically(partNamesPath, data, true); err != nil {
 		logger.Panicf("FATAL: cannot update %s: %s", partNamesPath, err)
 	}
 }
 
 func mustReadPartNames(srcDir string) []string {
-	partNamesPath := srcDir + "/parts.json"
+	partNamesPath := filepath.Join(srcDir, partsFilename)
 	data, err := os.ReadFile(partNamesPath)
 	if err == nil {
 		var partNames []string