Updates based on PR feedback

models/points.go

@@ -1146,7 +1146,7 @@ func (t Tags) HashKey() []byte {
 		ek := escapeTag([]byte(k))
 		ev := escapeTag([]byte(v))
 
-		if len(string(ev)) > 0 {
+		if len(ev) > 0 {
 			escaped[string(ek)] = string(ev)
 		}
 	}

tsdb/engine.go

@@ -71,7 +71,7 @@ func NewEngine(path string, walPath string, options EngineOptions) (Engine, erro
 		return newEngineFuncs[options.EngineVersion](path, walPath, options), nil
 	}
 
-	// Only bolt-based backends are currently supported so open it and check the format.
+	// Only bolt and tsm1 based storage engines are currently supported
 	var format string
 	if err := func() error {
 		// if it's a dir then it's a tsm1 engine

tsdb/engine/tsm1/cursor.go

@@ -6,6 +6,10 @@ import (
 	"github.com/influxdb/influxdb/tsdb"
 )
 
+// combinedEngineCursor holds a cursor for the WAL and the index
+// and will combine the two together. Any points in the WAL with
+// identical timestamps from the index will be preferred over the
+// index point
 type combinedEngineCursor struct {
 	walCursor      tsdb.Cursor
 	engineCursor   tsdb.Cursor
@@ -24,20 +28,26 @@ func NewCombinedEngineCursor(wc, ec tsdb.Cursor, ascending bool) tsdb.Cursor {
 	}
 }
 
+// SeekTo will seek both the index and WAL cursor
 func (c *combinedEngineCursor) SeekTo(seek int64) (key int64, value interface{}) {
 	c.walKeyBuf, c.walValueBuf = c.walCursor.SeekTo(seek)
 	c.engineKeyBuf, c.engineValueBuf = c.engineCursor.SeekTo(seek)
 	return c.read()
 }
 
+// Next returns the next value in the cursor
 func (c *combinedEngineCursor) Next() (int64, interface{}) {
 	return c.read()
 }
 
+// Ascending returns true if the cursor is time ascending
 func (c *combinedEngineCursor) Ascending() bool {
 	return c.ascending
 }
 
+// read will return the buffer value that is next from either the
+// WAL or index cursor and repopulate the buffer value with the
+// appropriate cursor's next value
 func (c *combinedEngineCursor) read() (key int64, value interface{}) {
 	if c.walKeyBuf == tsdb.EOF && c.engineKeyBuf == tsdb.EOF {
 		return tsdb.EOF, nil
@@ -84,6 +94,9 @@ func (c *combinedEngineCursor) read() (key int64, value interface{}) {
 	return
 }
 
+// multieFieldCursor wraps cursors for multiple fields on the same series
+// key. Instead of returning a plain interface value in the call for Next(),
+// it returns a map[string]interface{} for the field values
 type multiFieldCursor struct {
 	fields      []string
 	cursors     []tsdb.Cursor
@@ -158,18 +171,31 @@ func (c *emptyCursor) Next() (int64, interface{})            { return tsdb.EOF,
 func (c *emptyCursor) SeekTo(key int64) (int64, interface{}) { return tsdb.EOF, nil }
 func (c *emptyCursor) Ascending() bool                       { return c.ascending }
 
+// cursor is a cursor for the data in the index
 type cursor struct {
-	id       uint64
-	f        *dataFile
+	// id for the series key and field
+	id uint64
+
+	// f is the current data file we're reading from
+	f *dataFile
+
+	// filesPos is the position in the files index we're reading from
 	filesPos int // the index in the files slice we're looking at
-	pos      uint32
-	vals     Values
+
+	// pos is the position in the current data file we're reading
+	pos uint32
+
+	// vals is the current decoded block of Values we're iterating from
+	vals Values
 
 	ascending bool
 
-	blockPositions []uint32 // only used for descending queries
+	// blockPositions is used for descending queries to keep track
+	// of what positions in the current data file encoded blocks for
+	// the id exist at
+	blockPositions []uint32
 
-	// time acending list of data files
+	// time acending slice of read only data files
 	files []*dataFile
 }
 
@@ -334,10 +360,13 @@ func (c *cursor) seekDescending(seek int64) (int64, interface{}) {
 	return tsdb.EOF, nil
 }
 
+// blockMinTime is the minimum time for the block
 func (c *cursor) blockMinTime(pos uint32) int64 {
 	return int64(btou64(c.f.mmap[pos+12 : pos+20]))
 }
 
+// setBlockPositions will read the positions of all
+// blocks for the cursor id in the given data file
 func (c *cursor) setBlockPositions() {
 	pos := c.pos
 
@@ -431,6 +460,7 @@ func (c *cursor) blockLength(pos uint32) uint32 {
 	return btou32(c.f.mmap[pos+8 : pos+12])
 }
 
+// decodeBlock will decod the block and set the vals
 func (c *cursor) decodeBlock(position uint32) {
 	length := c.blockLength(position)
 	block := c.f.mmap[position+blockHeaderSize : position+blockHeaderSize+length]

tsdb/engine/tsm1/tsm1.go

@@ -80,6 +80,8 @@ const (
 	// MAP_POPULATE is for the mmap syscall. For some reason this isn't defined in golang's syscall
 	MAP_POPULATE = 0x8000
 
+	// magicNumber is written as the first 4 bytes of a data file to
+	// identify the file as a tsm1 formatted file
 	magicNumber uint32 = 0x16D116D1
 )
 
@@ -1298,6 +1300,8 @@ func (e *Engine) writeNewFileExcludeDeletes(oldDF *dataFile) *dataFile {
 }
 
 func (e *Engine) nextFileName() string {
+	e.filesLock.Lock()
+	defer e.filesLock.Unlock()
 	e.currentFileID++
 	return filepath.Join(e.path, fmt.Sprintf("%07d.%s", e.currentFileID, Format))
 }