remove unused changes variable (#391)

This was added in
55a9b5428a

and later not used after some refactoring in following PRs.

Signed-off-by: Krasi Georgiev <kgeorgie@redhat.com>

db.go

@@ -300,7 +300,7 @@ func (db *DB) run() {
 		case <-db.compactc:
 			db.metrics.compactionsTriggered.Inc()
 
-			_, err := db.compact()
+			err := db.compact()
 			if err != nil {
 				level.Error(db.logger).Log("msg", "compaction failed", "err", err)
 				backoff = exponential(backoff, 1*time.Second, 1*time.Minute)
@@ -366,12 +366,12 @@ func (a dbAppender) Commit() error {
 // this is sufficient to reliably delete old data.
 // Old blocks are only deleted on reload based on the new block's parent information.
 // See DB.reload documentation for further information.
-func (db *DB) compact() (changes bool, err error) {
+func (db *DB) compact() (err error) {
 	db.cmtx.Lock()
 	defer db.cmtx.Unlock()
 
 	if !db.compactionsEnabled {
-		return false, nil
+		return nil
 	}
 
 	// Check whether we have pending head blocks that are ready to be persisted.
@@ -379,7 +379,7 @@ func (db *DB) compact() (changes bool, err error) {
 	for {
 		select {
 		case <-db.stopc:
-			return changes, nil
+			return nil
 		default:
 		}
 		// The head has a compactable range if 1.5 level 0 ranges are between the oldest
@@ -402,14 +402,13 @@ func (db *DB) compact() (changes bool, err error) {
 			maxt: maxt - 1,
 		}
 		if _, err = db.compactor.Write(db.dir, head, mint, maxt, nil); err != nil {
-			return changes, errors.Wrap(err, "persist head block")
+			return errors.Wrap(err, "persist head block")
 		}
-		changes = true
 
 		runtime.GC()
 
 		if err := db.reload(); err != nil {
-			return changes, errors.Wrap(err, "reload blocks")
+			return errors.Wrap(err, "reload blocks")
 		}
 		runtime.GC()
 	}
@@ -418,7 +417,7 @@ func (db *DB) compact() (changes bool, err error) {
 	for {
 		plan, err := db.compactor.Plan(db.dir)
 		if err != nil {
-			return changes, errors.Wrap(err, "plan compaction")
+			return errors.Wrap(err, "plan compaction")
 		}
 		if len(plan) == 0 {
 			break
@@ -426,23 +425,22 @@ func (db *DB) compact() (changes bool, err error) {
 
 		select {
 		case <-db.stopc:
-			return changes, nil
+			return nil
 		default:
 		}
 
 		if _, err := db.compactor.Compact(db.dir, plan...); err != nil {
-			return changes, errors.Wrapf(err, "compact %s", plan)
+			return errors.Wrapf(err, "compact %s", plan)
 		}
-		changes = true
 		runtime.GC()
 
 		if err := db.reload(); err != nil {
-			return changes, errors.Wrap(err, "reload blocks")
+			return errors.Wrap(err, "reload blocks")
 		}
 		runtime.GC()
 	}
 
-	return changes, nil
+	return nil
 }
 
 func (db *DB) getBlock(id ulid.ULID) (*Block, bool) {

db_test.go

@@ -1131,7 +1131,7 @@ func TestChunkAtBlockBoundary(t *testing.T) {
 	err := app.Commit()
 	testutil.Ok(t, err)
 
-	_, err = db.compact()
+	err = db.compact()
 	testutil.Ok(t, err)
 
 	for _, block := range db.blocks {
@@ -1183,7 +1183,7 @@ func TestQuerierWithBoundaryChunks(t *testing.T) {
 	err := app.Commit()
 	testutil.Ok(t, err)
 
-	_, err = db.compact()
+	err = db.compact()
 	testutil.Ok(t, err)
 
 	testutil.Assert(t, len(db.blocks) >= 3, "invalid test, less than three blocks in DB")