diff --git a/flux/stdlib/universe/bare_aggregate_test.flux b/flux/stdlib/universe/bare_aggregate_test.flux
index e2c1bcf3bf..082ee5ed9f 100644
--- a/flux/stdlib/universe/bare_aggregate_test.flux
+++ b/flux/stdlib/universe/bare_aggregate_test.flux
@@ -177,7 +177,8 @@ testcase bare_last {
     )
     result = csv.from(csv: input)
         |> testing.load()
-        |> range(start: -100y)
+        |> range(start: 2015-01-01T00:00:00Z)
+        |> filter(fn: (r) => r._measurement == "pge_bill" and r._field == "bank")
         |> last()
         |> keep(columns: ["_time", "_value", "_field", "_measurement"])
 
diff --git a/tsdb/index/tsi1/partition.go b/tsdb/index/tsi1/partition.go
index 3d29882612..ca8f9a9555 100644
--- a/tsdb/index/tsi1/partition.go
+++ b/tsdb/index/tsi1/partition.go
@@ -39,7 +39,8 @@ const ManifestFileName = "MANIFEST"
 
 // Partition represents a collection of layered index files and WAL.
 type Partition struct {
-	mu     sync.RWMutex
+	// exported for tests
+	Mu     sync.RWMutex
 	opened bool
 
 	sfile         *tsdb.SeriesFile // series lookup file
@@ -150,8 +151,8 @@ var ErrIncompatibleVersion = errors.New("incompatible tsi1 index MANIFEST")
 
 // Open opens the partition.
 func (p *Partition) Open() (rErr error) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.Mu.Lock()
+	defer p.Mu.Unlock()
 
 	p.closing = make(chan struct{})
 
@@ -339,8 +340,8 @@ func (p *Partition) buildSeriesSet() error {
 
 // CurrentCompactionN returns the number of compactions currently running.
 func (p *Partition) CurrentCompactionN() int {
-	p.mu.RLock()
-	defer p.mu.RUnlock()
+	p.Mu.RLock()
+	defer p.Mu.RUnlock()
 	return p.currentCompactionN
 }
 
@@ -367,8 +368,8 @@ func (p *Partition) Close() error {
 	p.Wait()
 
 	// Lock index and close remaining
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.Mu.Lock()
+	defer p.Mu.Unlock()
 
 	var err error
 
@@ -402,8 +403,8 @@ func (p *Partition) SeriesFile() *tsdb.SeriesFile { return p.sfile }
 
 // NextSequence returns the next file identifier.
 func (p *Partition) NextSequence() int {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.Mu.Lock()
+	defer p.Mu.Unlock()
 	return p.nextSequence()
 }
 
@@ -445,8 +446,8 @@ func (p *Partition) manifest(newFileSet *FileSet) *Manifest {
 
 // SetManifestPathForTest is only to force a bad path in testing
 func (p *Partition) SetManifestPathForTest(path string) {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.Mu.Lock()
+	defer p.Mu.Unlock()
 	p.manifestPathFn = func() string { return path }
 }
 
@@ -457,16 +458,16 @@ func (p *Partition) WithLogger(logger *zap.Logger) {
 
 // SetFieldSet sets a shared field set from the engine.
 func (p *Partition) SetFieldSet(fs *tsdb.MeasurementFieldSet) {
-	p.mu.Lock()
+	p.Mu.Lock()
 	p.fieldset = fs
-	p.mu.Unlock()
+	p.Mu.Unlock()
 }
 
 // FieldSet returns the fieldset.
 func (p *Partition) FieldSet() *tsdb.MeasurementFieldSet {
-	p.mu.Lock()
+	p.Mu.Lock()
 	fs := p.fieldset
-	p.mu.Unlock()
+	p.Mu.Unlock()
 	return fs
 }
 
@@ -476,8 +477,8 @@ func (p *Partition) RetainFileSet() (*FileSet, error) {
 	case <-p.closing:
 		return nil, tsdb.ErrIndexClosing
 	default:
-		p.mu.RLock()
-		defer p.mu.RUnlock()
+		p.Mu.RLock()
+		defer p.Mu.RUnlock()
 		return p.retainFileSet(), nil
 	}
 }
@@ -490,8 +491,8 @@ func (p *Partition) retainFileSet() *FileSet {
 
 // FileN returns the active files in the file set.
 func (p *Partition) FileN() int {
-	p.mu.RLock()
-	defer p.mu.RUnlock()
+	p.Mu.RLock()
+	defer p.Mu.RUnlock()
 	return len(p.fileSet.files)
 }
 
@@ -671,12 +672,12 @@ func (p *Partition) DropMeasurement(name []byte) error {
 	// Mark measurement as deleted.
 	entries = append(entries, LogEntry{Flag: LogEntryMeasurementTombstoneFlag, Name: name})
 
-	p.mu.RLock()
+	p.Mu.RLock()
 	if err := p.activeLogFile.Writes(entries); err != nil {
-		p.mu.RUnlock()
+		p.Mu.RUnlock()
 		return err
 	}
-	p.mu.RUnlock()
+	p.Mu.RUnlock()
 
 	// Check if the log file needs to be swapped.
 	if err := p.CheckLogFile(); err != nil {
@@ -704,14 +705,14 @@ func (p *Partition) createSeriesListIfNotExists(names [][]byte, tagsSlice []mode
 	defer fs.Release()
 
 	// Ensure fileset cannot change during insert.
-	p.mu.RLock()
+	p.Mu.RLock()
 	// Insert series into log file.
 	ids, err := p.activeLogFile.AddSeriesList(p.seriesIDSet, names, tagsSlice, tracker)
 	if err != nil {
-		p.mu.RUnlock()
+		p.Mu.RUnlock()
 		return nil, err
 	}
-	p.mu.RUnlock()
+	p.Mu.RUnlock()
 
 	if err := p.CheckLogFile(); err != nil {
 		return nil, err
@@ -722,8 +723,8 @@ func (p *Partition) createSeriesListIfNotExists(names [][]byte, tagsSlice []mode
 func (p *Partition) DropSeries(seriesID uint64) error {
 	// Delete series from index.
 	if err := func() error {
-		p.mu.RLock()
-		defer p.mu.RUnlock()
+		p.Mu.RLock()
+		defer p.Mu.RUnlock()
 		return p.activeLogFile.DeleteSeriesID(seriesID)
 	}(); err != nil {
 		return err
@@ -742,8 +743,8 @@ func (p *Partition) DropSeriesList(seriesIDs []uint64) error {
 
 	// Delete series from index.
 	if err := func() error {
-		p.mu.RLock()
-		defer p.mu.RUnlock()
+		p.Mu.RLock()
+		defer p.Mu.RUnlock()
 		return p.activeLogFile.DeleteSeriesIDList(seriesIDs)
 	}(); err != nil {
 		return err
@@ -910,14 +911,14 @@ func (p *Partition) AssignShard(k string, shardID uint64)         {}
 
 // Compact requests a compaction of log files.
 func (p *Partition) Compact() {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.Mu.Lock()
+	defer p.Mu.Unlock()
 	p.compact()
 }
 
 func (p *Partition) DisableCompactions() {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.Mu.Lock()
+	defer p.Mu.Unlock()
 	p.compactionsDisabled++
 
 	select {
@@ -933,8 +934,8 @@ func (p *Partition) DisableCompactions() {
 }
 
 func (p *Partition) EnableCompactions() {
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.Mu.Lock()
+	defer p.Mu.Unlock()
 
 	// Already enabled?
 	if p.compactionsEnabled() {
@@ -952,9 +953,9 @@ func (p *Partition) runPeriodicCompaction() {
 	p.Compact()
 
 	// Avoid a race when using Reopen in tests
-	p.mu.RLock()
+	p.Mu.RLock()
 	closing := p.closing
-	p.mu.RUnlock()
+	p.Mu.RUnlock()
 
 	// check for compactions once an hour (usually not necessary but a nice safety check)
 	t := time.NewTicker(1 * time.Hour)
@@ -977,8 +978,8 @@ func (p *Partition) runPeriodicCompaction() {
 // If checkRunning = true, only count as needing a compaction if there is not a compaction already
 // in progress for the level that would be compacted
 func (p *Partition) NeedsCompaction(checkRunning bool) bool {
-	p.mu.RLock()
-	defer p.mu.RUnlock()
+	p.Mu.RLock()
+	defer p.Mu.RUnlock()
 	if p.needsLogCompaction() {
 		return true
 	}
@@ -1031,10 +1032,10 @@ func (p *Partition) compact() {
 			p.currentCompactionN++
 			go func() {
 				p.compactLogFile(logFile)
-				p.mu.Lock()
+				p.Mu.Lock()
 				p.currentCompactionN--
 				p.levelCompacting[0] = false
-				p.mu.Unlock()
+				p.Mu.Unlock()
 				p.Compact()
 			}()
 		}
@@ -1074,10 +1075,10 @@ func (p *Partition) compact() {
 				p.compactToLevel(files, level+1, interrupt)
 
 				// Ensure compaction lock for the level is released.
-				p.mu.Lock()
+				p.Mu.Lock()
 				p.levelCompacting[level] = false
 				p.currentCompactionN--
-				p.mu.Unlock()
+				p.Mu.Unlock()
 
 				// Check for new compactions
 				p.Compact()
@@ -1155,8 +1156,8 @@ func (p *Partition) compactToLevel(files []*IndexFile, level int, interrupt <-ch
 
 	// Obtain lock to swap in index file and write manifest.
 	if err := func() (rErr error) {
-		p.mu.Lock()
-		defer p.mu.Unlock()
+		p.Mu.Lock()
+		defer p.Mu.Unlock()
 
 		// Replace previous files with new index file.
 		newFileSet := p.fileSet.MustReplace(IndexFiles(files).Files(), file)
@@ -1220,8 +1221,8 @@ func (p *Partition) needsLogCompaction() bool {
 func (p *Partition) CheckLogFile() error {
 	// Check log file under read lock.
 	needsCompaction := func() bool {
-		p.mu.RLock()
-		defer p.mu.RUnlock()
+		p.Mu.RLock()
+		defer p.Mu.RUnlock()
 		return p.needsLogCompaction()
 	}()
 	if !needsCompaction {
@@ -1229,8 +1230,8 @@ func (p *Partition) CheckLogFile() error {
 	}
 
 	// If file size exceeded then recheck under write lock and swap files.
-	p.mu.Lock()
-	defer p.mu.Unlock()
+	p.Mu.Lock()
+	defer p.Mu.Unlock()
 	return p.checkLogFile()
 }
 
@@ -1260,9 +1261,9 @@ func (p *Partition) compactLogFile(logFile *LogFile) {
 		return
 	}
 
-	p.mu.Lock()
+	p.Mu.Lock()
 	interrupt := p.compactionInterrupt
-	p.mu.Unlock()
+	p.Mu.Unlock()
 
 	start := time.Now()
 
@@ -1312,8 +1313,8 @@ func (p *Partition) compactLogFile(logFile *LogFile) {
 
 	// Obtain lock to swap in index file and write manifest.
 	if err := func() (rErr error) {
-		p.mu.Lock()
-		defer p.mu.Unlock()
+		p.Mu.Lock()
+		defer p.Mu.Unlock()
 
 		// Replace previous log file with index file.
 		newFileSet := p.fileSet.MustReplace([]File{logFile}, file)
diff --git a/tsdb/index/tsi1/partition_test.go b/tsdb/index/tsi1/partition_test.go
index 211f2103a4..07d74be7a8 100644
--- a/tsdb/index/tsi1/partition_test.go
+++ b/tsdb/index/tsi1/partition_test.go
@@ -74,9 +74,19 @@ func TestPartition_Open(t *testing.T) {
 func TestPartition_Manifest(t *testing.T) {
 	t.Run("current MANIFEST", func(t *testing.T) {
 		sfile := MustOpenSeriesFile()
-		defer sfile.Close()
+		t.Cleanup(func() {
+			if err := sfile.Close(); err != nil {
+				t.Fatalf("error closing series file %v", err)
+			}
+		})
 
 		p := MustOpenPartition(sfile.SeriesFile)
+		t.Cleanup(func() {
+			if err := p.Close(); err != nil {
+				t.Fatalf("error closing partition %v", err)
+			}
+		})
+
 		if got, exp := p.Manifest().Version, tsi1.Version; got != exp {
 			t.Fatalf("got MANIFEST version %d, expected %d", got, exp)
 		}
@@ -98,14 +108,17 @@ func TestPartition_Manifest_Write_Fail(t *testing.T) {
 func TestPartition_PrependLogFile_Write_Fail(t *testing.T) {
 	t.Run("write MANIFEST", func(t *testing.T) {
 		sfile := MustOpenSeriesFile()
-		defer sfile.Close()
-
+		t.Cleanup(func() {
+			if err := sfile.Close(); err != nil {
+				t.Fatalf("error closing series file %v", err)
+			}
+		})
 		p := MustOpenPartition(sfile.SeriesFile)
-		defer func() {
+		t.Cleanup(func() {
 			if err := p.Close(); err != nil {
 				t.Fatalf("error closing partition: %v", err)
 			}
-		}()
+		})
 		p.Partition.MaxLogFileSize = -1
 		fileN := p.FileN()
 		p.CheckLogFile()
@@ -124,15 +137,21 @@ func TestPartition_PrependLogFile_Write_Fail(t *testing.T) {
 func TestPartition_Compact_Write_Fail(t *testing.T) {
 	t.Run("write MANIFEST", func(t *testing.T) {
 		sfile := MustOpenSeriesFile()
-		defer sfile.Close()
+		t.Cleanup(func() {
+			if err := sfile.Close(); err != nil {
+				t.Fatalf("error closing series file %v", err)
+			}
+		})
 
 		p := MustOpenPartition(sfile.SeriesFile)
-		defer func() {
+		t.Cleanup(func() {
 			if err := p.Close(); err != nil {
 				t.Fatalf("error closing partition: %v", err)
 			}
-		}()
+		})
+		p.Partition.Mu.Lock()
 		p.Partition.MaxLogFileSize = -1
+		p.Partition.Mu.Unlock()
 		fileN := p.FileN()
 		p.Compact()
 		if (1 + fileN) != p.FileN() {