fix delete expired keys

Author: roseduan

db.go

@@ -1,7 +1,6 @@
 package rosedb
 
 import (
-	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -354,11 +353,10 @@ func (db *DB) Ascend(handleFn func(k []byte, v []byte) (bool, error)) {
 		if err != nil {
 			return false, err
 		}
-		value, err := db.checkValue(chunk)
-		if err != nil {
-			return false, err
+		if value := db.checkValue(chunk); value != nil {
+			return handleFn(key, value)
 		}
-		return handleFn(key, value)
+		return true, nil
 	})
 }
 
@@ -372,11 +370,10 @@ func (db *DB) AscendRange(startKey, endKey []byte, handleFn func(k []byte, v []b
 		if err != nil {
 			return false, nil
 		}
-		value, err := db.checkValue(chunk)
-		if err != nil {
-			return false, err
+		if value := db.checkValue(chunk); value != nil {
+			return handleFn(key, value)
 		}
-		return handleFn(key, value)
+		return true, nil
 	})
 }
 
@@ -390,11 +387,10 @@ func (db *DB) AscendGreaterOrEqual(key []byte, handleFn func(k []byte, v []byte)
 		if err != nil {
 			return false, nil
 		}
-		value, err := db.checkValue(chunk)
-		if err != nil {
-			return false, err
+		if value := db.checkValue(chunk); value != nil {
+			return handleFn(key, value)
 		}
-		return handleFn(key, value)
+		return true, nil
 	})
 }
 
@@ -426,11 +422,10 @@ func (db *DB) Descend(handleFn func(k []byte, v []byte) (bool, error)) {
 		if err != nil {
 			return false, nil
 		}
-		value, err := db.checkValue(chunk)
-		if err != nil {
-			return false, err
+		if value := db.checkValue(chunk); value != nil {
+			return handleFn(key, value)
 		}
-		return handleFn(key, value)
+		return true, nil
 	})
 }
 
@@ -444,11 +439,10 @@ func (db *DB) DescendRange(startKey, endKey []byte, handleFn func(k []byte, v []
 		if err != nil {
 			return false, nil
 		}
-		value, err := db.checkValue(chunk)
-		if err != nil {
-			return false, err
+		if value := db.checkValue(chunk); value != nil {
+			return handleFn(key, value)
 		}
-		return handleFn(key, value)
+		return true, nil
 	})
 }
 
@@ -462,11 +456,10 @@ func (db *DB) DescendLessOrEqual(key []byte, handleFn func(k []byte, v []byte) (
 		if err != nil {
 			return false, nil
 		}
-		value, err := db.checkValue(chunk)
-		if err != nil {
-			return false, err
+		if value := db.checkValue(chunk); value != nil {
+			return handleFn(key, value)
 		}
-		return handleFn(key, value)
+		return true, nil
 	})
 }
 
@@ -488,13 +481,13 @@ func (db *DB) DescendKeys(pattern []byte, handleFn func(k []byte) (bool, error))
 	})
 }
 
-func (db *DB) checkValue(chunk []byte) ([]byte, error) {
+func (db *DB) checkValue(chunk []byte) []byte {
 	record := decodeLogRecord(chunk)
 	now := time.Now().UnixNano()
-	if record.Type == LogRecordDeleted || record.IsExpired(now) {
-		return nil, ErrKeyNotFound
+	if record.Type != LogRecordDeleted && !record.IsExpired(now) {
+		return record.Value
 	}
-	return record.Value, nil
+	return nil
 }
 
 func checkOptions(options Options) error {
@@ -585,21 +578,18 @@ func (db *DB) DeleteExpiredKeys(timeout time.Duration) error {
 	db.mu.Lock()
 	defer db.mu.Unlock()
 
-	// set expiration time
+	// set timeout
 	ctx, cancel := context.WithTimeout(context.Background(), timeout)
 	defer cancel()
+	done := make(chan struct{}, 1)
 
-	innerErrs := make([]error, 0) // record anonymous func error
+	var innerErr error
 	now := time.Now().UnixNano()
 	go func(ctx context.Context) {
 		for {
-			// get 100 key's positions
+			// select 100 keys from the db.index
 			positions := make([]*wal.ChunkPosition, 0, 100)
 			db.index.AscendGreaterOrEqual(db.expiredCursorKey, func(k []byte, pos *wal.ChunkPosition) (bool, error) {
-				// filter processed key
-				if bytes.Compare(k, db.expiredCursorKey) == 0 {
-					return true, nil
-				}
 				positions = append(positions, pos)
 				if len(positions) >= 100 {
 					return false, nil
@@ -610,14 +600,16 @@ func (db *DB) DeleteExpiredKeys(timeout time.Duration) error {
 			// If keys in the db.index has been traversed, len(positions) will be 0.
 			if len(positions) == 0 {
 				db.expiredCursorKey = nil
+				done <- struct{}{}
 				return
 			}
 
 			// delete from index if the key is expired.
 			for _, pos := range positions {
 				chunk, err := db.dataFiles.Read(pos)
 				if err != nil {
-					innerErrs = append(innerErrs, err)
+					innerErr = err
+					done <- struct{}{}
 					return
 				}
 				record := decodeLogRecord(chunk)
@@ -631,9 +623,8 @@ func (db *DB) DeleteExpiredKeys(timeout time.Duration) error {
 
 	select {
 	case <-ctx.Done():
-		if len(innerErrs) > 0 {
-			return innerErrs[0]
-		}
+		return innerErr
+	case <-done:
 		return nil
 	}
 }