fix data race on index metadata (docCount)

closes #198

index/upside_down/upside_down.go

@@ -14,6 +14,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"math"
+	"sync"
 	"sync/atomic"
 	"time"
 
@@ -36,9 +37,12 @@ type UpsideDownCouch struct {
 	path            string
 	store           store.KVStore
 	fieldIndexCache *FieldIndexCache
-	docCount        uint64
 	analysisQueue   *AnalysisQueue
 	stats           *indexStat
+
+	m sync.RWMutex
+	// fields protected by m
+	docCount uint64
 }
 
 func NewUpsideDownCouch(s store.KVStore, analysisQueue *AnalysisQueue) *UpsideDownCouch {
@@ -149,6 +153,8 @@ func (udc *UpsideDownCouch) batchRows(writer store.KVWriter, addRows []UpsideDow
 }
 
 func (udc *UpsideDownCouch) DocCount() (uint64, error) {
+	udc.m.RLock()
+	defer udc.m.RUnlock()
 	return udc.docCount, nil
 }
 
@@ -193,7 +199,9 @@ func (udc *UpsideDownCouch) Open() (err error) {
 		}
 	}
 	// set doc count
+	udc.m.Lock()
 	udc.docCount, err = udc.countDocs(kvwriter)
+	udc.m.Unlock()
 	return
 }
 
@@ -300,7 +308,9 @@ func (udc *UpsideDownCouch) Update(doc *document.Document) (err error) {
 
 	err = udc.batchRows(kvwriter, addRows, updateRows, deleteRows)
 	if err == nil && backIndexRow == nil {
+		udc.m.Lock()
 		udc.docCount++
+		udc.m.Unlock()
 	}
 	atomic.AddUint64(&udc.stats.indexTime, uint64(time.Since(indexStart)))
 	if err == nil {
@@ -451,7 +461,9 @@ func (udc *UpsideDownCouch) Delete(id string) (err error) {
 
 	err = udc.batchRows(kvwriter, nil, nil, deleteRows)
 	if err == nil {
+		udc.m.Lock()
 		udc.docCount--
+		udc.m.Unlock()
 	}
 	atomic.AddUint64(&udc.stats.indexTime, uint64(time.Since(indexStart)))
 	if err == nil {
@@ -663,8 +675,10 @@ func (udc *UpsideDownCouch) Batch(batch *index.Batch) (err error) {
 	err = udc.batchRows(kvwriter, addRows, updateRows, deleteRows)
 	atomic.AddUint64(&udc.stats.indexTime, uint64(time.Since(indexStart)))
 	if err == nil {
+		udc.m.Lock()
 		udc.docCount += docsAdded
 		udc.docCount -= docsDeleted
+		udc.m.Unlock()
 		atomic.AddUint64(&udc.stats.updates, numUpdates)
 		atomic.AddUint64(&udc.stats.deletes, docsDeleted)
 		atomic.AddUint64(&udc.stats.batches, 1)
@@ -709,6 +723,8 @@ func (udc *UpsideDownCouch) Reader() (index.IndexReader, error) {
 	if err != nil {
 		return nil, fmt.Errorf("error opening store reader: %v", err)
 	}
+	udc.m.RLock()
+	defer udc.m.RUnlock()
 	return &IndexReader{
 		index:    udc,
 		kvreader: kvr,

index_test.go

@@ -607,3 +607,36 @@ func TestBatchString(t *testing.T) {
 	}
 
 }
+
+func TestIndexMetadataRaceBug198(t *testing.T) {
+	defer func() {
+		err := os.RemoveAll("testidx")
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	index, err := New("testidx", NewIndexMapping())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	go func() {
+		for {
+			index.DocCount()
+		}
+	}()
+
+	for i := 0; i < 100; i++ {
+		batch := index.NewBatch()
+		err = batch.Index("a", []byte("{}"))
+		if err != nil {
+			t.Fatal(err)
+		}
+		err = index.Batch(batch)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+}