Change else-if statements to idiomatic switch statements. (#1207)

(cherry picked from commit eee1602)

Author: martinmr

db.go

@@ -146,7 +146,8 @@ func (db *DB) replayFunction() func(Entry, valuePointer) error {
 			ExpiresAt: e.ExpiresAt,
 		}
 
-		if e.meta&bitFinTxn > 0 {
+		switch {
+		case e.meta&bitFinTxn > 0:
 			txnTs, err := strconv.ParseUint(string(e.Value), 10, 64)
 			if err != nil {
 				return errors.Wrapf(err, "Unable to parse txn fin: %q", e.Value)
@@ -160,7 +161,7 @@ func (db *DB) replayFunction() func(Entry, valuePointer) error {
 			txn = txn[:0]
 			lastCommit = 0
 
-		} else if e.meta&bitTxn > 0 {
+		case e.meta&bitTxn > 0:
 			txnTs := y.ParseTs(nk)
 			if lastCommit == 0 {
 				lastCommit = txnTs
@@ -174,7 +175,7 @@ func (db *DB) replayFunction() func(Entry, valuePointer) error {
 			te := txnEntry{nk: nk, v: v}
 			txn = append(txn, te)
 
-		} else {
+		default:
 			// This entry is from a rewrite.
 			toLSM(nk, v)
 
@@ -1055,9 +1056,10 @@ func (db *DB) calculateSize() {
 				return err
 			}
 			ext := filepath.Ext(path)
-			if ext == ".sst" {
+			switch ext {
+			case ".sst":
 				lsmSize += info.Size()
-			} else if ext == ".vlog" {
+			case ".vlog":
 				vlogSize += info.Size()
 			}
 			return nil
@@ -1214,11 +1216,12 @@ func (seq *Sequence) Release() error {
 func (seq *Sequence) updateLease() error {
 	return seq.db.Update(func(txn *Txn) error {
 		item, err := txn.Get(seq.key)
-		if err == ErrKeyNotFound {
+		switch {
+		case err == ErrKeyNotFound:
 			seq.next = 0
-		} else if err != nil {
+		case err != nil:
 			return err
-		} else {
+		default:
 			var num uint64
 			if err := item.Value(func(v []byte) error {
 				num = binary.BigEndian.Uint64(v)

levels.go

@@ -84,12 +84,13 @@ func newLevelsController(db *DB, mf *Manifest) (*levelsController, error) {
 
 	for i := 0; i < db.opt.MaxLevels; i++ {
 		s.levels[i] = newLevelHandler(db, i)
-		if i == 0 {
+		switch i {
+		case 0:
 			// Do nothing.
-		} else if i == 1 {
+		case 1:
 			// Level 1 probably shouldn't be too much bigger than level 0.
 			s.levels[i].maxTotalSize = db.opt.LevelOneSize
-		} else {
+		default:
 			s.levels[i].maxTotalSize = s.levels[i-1].maxTotalSize * int64(db.opt.LevelSizeMultiplier)
 		}
 		s.cstatus.levels[i] = new(levelCompactStatus)
@@ -360,12 +361,15 @@ func (s *levelsController) runWorker(lc *y.Closer) {
 		// Can add a done channel or other stuff.
 		case <-ticker.C:
 			prios := s.pickCompactLevels()
+		loop:
 			for _, p := range prios {
-				if err := s.doCompact(p); err == nil {
-					break
-				} else if err == errFillTables {
+				err := s.doCompact(p)
+				switch err {
+				case nil:
+					break loop
+				case errFillTables:
 					// pass
-				} else {
+				default:
 					s.kv.opt.Warningf("While running doCompact: %v\n", err)
 				}
 			}
@@ -475,9 +479,10 @@ func (s *levelsController) compactBuildTables(
 
 	// Create iterators across all the tables involved first.
 	var iters []y.Iterator
-	if lev == 0 {
+	switch {
+	case lev == 0:
 		iters = appendIteratorsReversed(iters, topTables, false)
-	} else if len(topTables) > 0 {
+	case len(topTables) > 0:
 		y.AssertTrue(len(topTables) == 1)
 		iters = []y.Iterator{topTables[0].NewIterator(false)}
 	}
@@ -579,14 +584,15 @@ func (s *levelsController) compactBuildTables(
 					// versions. Ensure that we're only removing versions below readTs.
 					skipKey = y.SafeCopy(skipKey, it.Key())
 
-					if lastValidVersion {
+					switch {
+					case lastValidVersion:
 						// Add this key. We have set skipKey, so the following key versions
 						// would be skipped.
-					} else if hasOverlap {
+					case hasOverlap:
 						// If this key range has overlap with lower levels, then keep the deletion
 						// marker with the latest version, discarding the rest. We have set skipKey,
 						// so the following key versions would be skipped.
-					} else {
+					default:
 						// If no overlap, we can skip all the versions, by continuing here.
 						numSkips++
 						updateStats(vs)

table/merge_iterator.go

@@ -55,17 +55,18 @@ func (n *node) setIterator(iter y.Iterator) {
 }
 
 func (n *node) setKey() {
-	if n.merge != nil {
+	switch {
+	case n.merge != nil:
 		n.valid = n.merge.small.valid
 		if n.valid {
 			n.key = n.merge.small.key
 		}
-	} else if n.concat != nil {
+	case n.concat != nil:
 		n.valid = n.concat.Valid()
 		if n.valid {
 			n.key = n.concat.Key()
 		}
-	} else {
+	default:
 		n.valid = n.iter.Valid()
 		if n.valid {
 			n.key = n.iter.Key()
@@ -74,11 +75,12 @@ func (n *node) setKey() {
 }
 
 func (n *node) next() {
-	if n.merge != nil {
+	switch {
+	case n.merge != nil:
 		n.merge.Next()
-	} else if n.concat != nil {
+	case n.concat != nil:
 		n.concat.Next()
-	} else {
+	default:
 		n.iter.Next()
 	}
 	n.setKey()
@@ -103,22 +105,22 @@ func (mi *MergeIterator) fix() {
 		return
 	}
 	cmp := y.CompareKeys(mi.small.key, mi.bigger().key)
-	// Both the keys are equal.
-	if cmp == 0 {
+	switch {
+	case cmp == 0: // Both the keys are equal.
 		// In case of same keys, move the right iterator ahead.
 		mi.right.next()
 		if &mi.right == mi.small {
 			mi.swapSmall()
 		}
 		return
-	} else if cmp < 0 { // Small is less than bigger().
+	case cmp < 0: // Small is less than bigger().
 		if mi.reverse {
 			mi.swapSmall()
 		} else {
 			// we don't need to do anything. Small already points to the smallest.
 		}
 		return
-	} else { // bigger() is less than small.
+	default: // bigger() is less than small.
 		if mi.reverse {
 			// Do nothing since we're iterating in reverse. Small currently points to
 			// the bigger key and that's okay in reverse iteration.
@@ -206,11 +208,12 @@ func (mi *MergeIterator) Close() error {
 
 // NewMergeIterator creates a merge iterator.
 func NewMergeIterator(iters []y.Iterator, reverse bool) y.Iterator {
-	if len(iters) == 0 {
+	switch len(iters) {
+	case 0:
 		return nil
-	} else if len(iters) == 1 {
+	case 1:
 		return iters[0]
-	} else if len(iters) == 2 {
+	case 2:
 		mi := &MergeIterator{
 			reverse: reverse,
 		}

value.go

@@ -436,15 +436,18 @@ func (vlog *valueLog) iterate(lf *logFile, offset uint32, fn logEntry) (uint32,
 
 	var lastCommit uint64
 	var validEndOffset uint32 = offset
+
+loop:
 	for {
 		e, err := read.Entry(reader)
-		if err == io.EOF {
-			break
-		} else if err == io.ErrUnexpectedEOF || err == errTruncate {
-			break
-		} else if err != nil {
+		switch {
+		case err == io.EOF:
+			break loop
+		case err == io.ErrUnexpectedEOF || err == errTruncate:
+			break loop
+		case err != nil:
 			return 0, err
-		} else if e == nil {
+		case e == nil:
 			continue
 		}
 
@@ -455,29 +458,30 @@ func (vlog *valueLog) iterate(lf *logFile, offset uint32, fn logEntry) (uint32,
 		vp.Offset = e.offset
 		vp.Fid = lf.fid
 
-		if e.meta&bitTxn > 0 {
+		switch {
+		case e.meta&bitTxn > 0:
 			txnTs := y.ParseTs(e.Key)
 			if lastCommit == 0 {
 				lastCommit = txnTs
 			}
 			if lastCommit != txnTs {
-				break
+				break loop
 			}
 
-		} else if e.meta&bitFinTxn > 0 {
+		case e.meta&bitFinTxn > 0:
 			txnTs, err := strconv.ParseUint(string(e.Value), 10, 64)
 			if err != nil || lastCommit != txnTs {
-				break
+				break loop
 			}
 			// Got the end of txn. Now we can store them.
 			lastCommit = 0
 			validEndOffset = read.recordOffset
 
-		} else {
+		default:
 			if lastCommit != 0 {
 				// This is most likely an entry which was moved as part of GC.
 				// We shouldn't get this entry in the middle of a transaction.
-				break
+				break loop
 			}
 			validEndOffset = read.recordOffset
 		}
@@ -1537,10 +1541,11 @@ func (vlog *valueLog) pickLog(head valuePointer, tr trace.Trace) (files []*logFi
 	vlog.filesLock.RLock()
 	defer vlog.filesLock.RUnlock()
 	fids := vlog.sortedFids()
-	if len(fids) <= 1 {
+	switch {
+	case len(fids) <= 1:
 		tr.LazyPrintf("Only one or less value log file.")
 		return nil
-	} else if head.Fid == 0 {
+	case head.Fid == 0:
 		tr.LazyPrintf("Head pointer is at zero.")
 		return nil
 	}