add scan command

database/keys.go

@@ -59,26 +59,36 @@ func execFlushDB(db *DB, args [][]byte) redis.Reply {
 	return &protocol.OkReply{}
 }
 
-// execType returns the type of entity, including: string, list, hash, set and zset
-func execType(db *DB, args [][]byte) redis.Reply {
-	key := string(args[0])
+// returns the type of entity, including: string, list, hash, set and zset
+func getType(db *DB, key string) string {
 	entity, exists := db.GetEntity(key)
 	if !exists {
-		return protocol.MakeStatusReply("none")
+		return "none"
 	}
 	switch entity.Data.(type) {
 	case []byte:
-		return protocol.MakeStatusReply("string")
+		return "string"
 	case list.List:
-		return protocol.MakeStatusReply("list")
+		return "list"
 	case dict.Dict:
-		return protocol.MakeStatusReply("hash")
+		return "hash"
 	case *set.Set:
-		return protocol.MakeStatusReply("set")
+		return "set"
 	case *sortedset.SortedSet:
-		return protocol.MakeStatusReply("zset")
+		return "zset"
+	}
+	return ""
+}
+
+// execType returns the type of entity, including: string, list, hash, set and zset
+func execType(db *DB, args [][]byte) redis.Reply {
+	key := string(args[0])
+	result := getType(db, key)
+	if len(result) > 0 {
+		return protocol.MakeStatusReply(result)
+	} else {
+		return &protocol.UnknownErrReply{}
 	}
-	return &protocol.UnknownErrReply{}
 }
 
 func prepareRename(args [][]byte) ([]string, []string) {
@@ -413,6 +423,57 @@ func execCopy(mdb *Server, conn redis.Connection, args [][]byte) redis.Reply {
 	return protocol.MakeIntReply(1)
 }
 
+// execScan return the result of the scan
+func execScan(db *DB, args [][]byte) redis.Reply {
+	var count int = 10
+	var pattern string = "*"
+	var scanType string = ""
+	if len(args) > 1 {
+		for i := 1; i < len(args); i++ {
+			arg := strings.ToLower(string(args[i]))
+			if arg == "count" {
+				count0, err := strconv.Atoi(string(args[i+1]))
+				if err != nil {
+					return &protocol.SyntaxErrReply{}
+				}
+				count = count0
+				i++
+			} else if arg == "match" {
+				pattern = string(args[i+1])
+				i++
+			} else if arg == "type" {
+				scanType = strings.ToLower(string(args[i+1]))
+				i++
+			} else {
+				return &protocol.SyntaxErrReply{}
+			}
+		}
+	}
+	cursor, err := strconv.Atoi(string(args[0]))
+	if err != nil {
+		return protocol.MakeErrReply("ERR invalid cursor")
+	}
+	keysReply, nextCursor := db.data.DictScan(cursor, count, pattern)
+	if nextCursor < 0 {
+		return protocol.MakeErrReply("Invalid argument")
+	}
+
+	if len(scanType) != 0 {
+		for i := 0; i < len(keysReply); {
+			if getType(db, string(keysReply[i])) != scanType {
+				keysReply = append(keysReply[:i], keysReply[i+1:]...)
+			} else {
+				i++
+			}
+		}
+	}
+	result := make([]redis.Reply, 2)
+	result[0] = protocol.MakeBulkReply([]byte(strconv.FormatInt(int64(nextCursor), 10)))
+	result[1] = protocol.MakeMultiBulkReply(keysReply)
+
+	return protocol.MakeMultiRawReply(result)
+}
+
 func init() {
 	registerCommand("Del", execDel, writeAllKeys, undoDel, -2, flagWrite).
 		attachCommandExtra([]string{redisFlagWrite}, 1, -1, 1)
@@ -444,4 +505,6 @@ func init() {
 		attachCommandExtra([]string{redisFlagWrite, redisFlagFast}, 1, 1, 1)
 	registerCommand("Keys", execKeys, noPrepare, nil, 2, flagReadOnly).
 		attachCommandExtra([]string{redisFlagReadonly, redisFlagSortForScript}, 1, 1, 1)
+	registerCommand("Scan", execScan, readAllKeys, nil, -2, flagReadOnly).
+		attachCommandExtra([]string{redisFlagReadonly, redisFlagSortForScript}, 1, 1, 1)
 }

database/keys_test.go

@@ -313,3 +313,85 @@ func TestCopy(t *testing.T) {
 	result = testMDB.Exec(conn, utils.ToCmdLine("ttl", destKey))
 	asserts.AssertIntReplyGreaterThan(t, result, 0)
 }
+
+func TestScan(t *testing.T) {
+	testDB.Flush()
+	for i := 0; i < 3; i++ {
+		key := string(rune(i))
+		value := key
+		testDB.Exec(nil, utils.ToCmdLine("set", "a:"+key, value))
+	}
+	for i := 0; i < 3; i++ {
+		key := string(rune(i))
+		value := key
+		testDB.Exec(nil, utils.ToCmdLine("set", "b:"+key, value))
+	}
+
+	// test scan 0 when keys < 10
+	result := testDB.Exec(nil, utils.ToCmdLine("scan", "0"))
+	cursorStr := string(result.(*protocol.MultiRawReply).Replies[0].(*protocol.BulkReply).Arg)
+	cursor, err := strconv.Atoi(cursorStr)
+	if err == nil {
+		if cursor != 0 {
+			t.Errorf("expect cursor 0, actually %d", cursor)
+			return
+		}
+	} else {
+		t.Errorf("get scan result error")
+		return
+	}
+
+	// test scan 0 match a*
+	result = testDB.Exec(nil, utils.ToCmdLine("scan", "0", "match", "a*"))
+	returnKeys := result.(*protocol.MultiRawReply).Replies[1].(*protocol.MultiBulkReply).Args
+	for i := range returnKeys {
+		key := string(returnKeys[i])
+		if key[0] != 'a' {
+			t.Errorf("The key %s should match a*", key)
+			return
+		}
+	}
+
+	// test scan 0 type string
+	testDB.Exec(nil, utils.ToCmdLine("hset", "hashkey", "hashkey", "1"))
+	result = testDB.Exec(nil, utils.ToCmdLine("scan", "0", "type", "string"))
+	returnKeys = result.(*protocol.MultiRawReply).Replies[1].(*protocol.MultiBulkReply).Args
+	for i := range returnKeys {
+		key := string(returnKeys[i])
+		if key == "hashkey" {
+			t.Errorf("expect type string, found hash")
+			return
+		}
+	}
+
+	// test returned cursor
+	testDB.Flush()
+	for i := 0; i < 100; i++ {
+		key := string(rune(i))
+		value := key
+		testDB.Exec(nil, utils.ToCmdLine("set", "a"+key, value))
+	}
+	cursor = 0
+	resultByte := make([][]byte, 0)
+	for {
+		scanCursor := strconv.Itoa(cursor)
+		result = testDB.Exec(nil, utils.ToCmdLine("scan", scanCursor, "count", "20"))
+		cursorStr := string(result.(*protocol.MultiRawReply).Replies[0].(*protocol.BulkReply).Arg)
+		returnKeys = result.(*protocol.MultiRawReply).Replies[1].(*protocol.MultiBulkReply).Args
+		resultByte = append(resultByte, returnKeys...)
+		cursor, err = strconv.Atoi(cursorStr)
+		if err == nil {
+			if cursor == 0 {
+				break
+			}
+		} else {
+			t.Errorf("get scan result error")
+			return
+		}
+	}
+	resultByte = utils.RemoveDuplicates(resultByte)
+	if len(resultByte) != 100 {
+		t.Errorf("expect result num 100, actually %d", len(resultByte))
+		return
+	}
+}

datastruct/dict/concurrent.go

@@ -1,6 +1,7 @@
 package dict
 
 import (
+	"github.com/hdt3213/godis/lib/wildcard"
 	"math"
 	"math/rand"
 	"sort"
@@ -435,3 +436,47 @@ func (dict *ConcurrentDict) RWUnLocks(writeKeys []string, readKeys []string) {
 		}
 	}
 }
+
+func stringsToBytes(strSlice []string) [][]byte {
+	byteSlice := make([][]byte, len(strSlice))
+	for i, str := range strSlice {
+		byteSlice[i] = []byte(str)
+	}
+	return byteSlice
+}
+
+func (dict *ConcurrentDict) DictScan(cursor int, count int, pattern string) ([][]byte, int) {
+	size := dict.Len()
+	result := make([][]byte, 0)
+
+	if pattern == "*" && count >= size {
+		return stringsToBytes(dict.Keys()), 0
+	}
+
+	matchKey, err := wildcard.CompilePattern(pattern)
+	if err != nil {
+		return result, -1
+	}
+
+	shardCount := len(dict.table)
+	shardIndex := cursor
+
+	for shardIndex < shardCount {
+		shard := dict.table[shardIndex]
+		shard.mutex.RLock()
+		if len(result)+len(shard.m) > count && shardIndex > cursor {
+			shard.mutex.RUnlock()
+			return result, shardIndex
+		}
+
+		for key := range shard.m {
+			if pattern == "*" || matchKey.IsMatch(key) {
+				result = append(result, []byte(key))
+			}
+		}
+		shard.mutex.RUnlock()
+		shardIndex++
+	}
+
+	return result, 0
+}

datastruct/dict/concurrent_test.go

@@ -465,7 +465,7 @@ func TestConcurrentRemoveWithLock(t *testing.T) {
 	}
 }
 
-//change t.Error remove->forEach
+// change t.Error remove->forEach
 func TestConcurrentForEach(t *testing.T) {
 	d := MakeConcurrent(0)
 	size := 100
@@ -524,3 +524,51 @@ func TestConcurrentDict_Keys(t *testing.T) {
 		t.Errorf("expect %d keys, actual: %d", size, len(d.Keys()))
 	}
 }
+
+func TestDictScan(t *testing.T) {
+	d := MakeConcurrent(0)
+	count := 100
+	for i := 0; i < count; i++ {
+		key := "kkk" + strconv.Itoa(i)
+		d.Put(key, i)
+	}
+	for i := 0; i < count; i++ {
+		key := "key" + strconv.Itoa(i)
+		d.Put(key, i)
+	}
+	cursor := 0
+	matchKey := "*"
+	c := 20
+	result := make([][]byte, 0)
+	var returnKeys [][]byte
+	for {
+		returnKeys, cursor = d.DictScan(cursor, c, matchKey)
+		result = append(result, returnKeys...)
+		if cursor == 0 {
+			break
+		}
+	}
+	result = utils.RemoveDuplicates(result)
+	if len(result) != count*2 {
+		t.Errorf("scan command result number error: %d, should be %d ", len(result), count*2)
+	}
+	matchKey = "key*"
+	cursor = 0
+	mresult := make([][]byte, 0)
+	for {
+		returnKeys, cursor = d.DictScan(cursor, c, matchKey)
+		mresult = append(mresult, returnKeys...)
+		if cursor == 0 {
+			break
+		}
+	}
+	mresult = utils.RemoveDuplicates(mresult)
+	if len(mresult) != count {
+		t.Errorf("scan command result number error: %d, should be %d ", len(mresult), count)
+	}
+	matchKey = "no*"
+	returnKeys, _ = d.DictScan(cursor, c, matchKey)
+	if len(returnKeys) != 0 {
+		t.Errorf("returnKeys should be empty")
+	}
+}

datastruct/dict/dict.go

@@ -16,4 +16,5 @@ type Dict interface {
 	RandomKeys(limit int) []string
 	RandomDistinctKeys(limit int) []string
 	Clear()
+	DictScan(cursor int, count int, pattern string) ([][]byte, int)
 }

datastruct/dict/simple.go

@@ -120,3 +120,7 @@ func (dict *SimpleDict) RandomDistinctKeys(limit int) []string {
 func (dict *SimpleDict) Clear() {
 	*dict = *MakeSimple()
 }
+
+func (dict *SimpleDict) DictScan(cursor int, count int, pattern string) ([][]byte, int) {
+	return stringsToBytes(dict.Keys()), 0
+}

lib/utils/utils.go

@@ -84,3 +84,20 @@ func ConvertRange(start int64, end int64, size int64) (int, int) {
 	}
 	return int(start), int(end)
 }
+
+// RemoveDuplicates removes duplicate byte slices from a 2D byte slice
+func RemoveDuplicates(input [][]byte) [][]byte {
+	uniqueMap := make(map[string]struct{})
+	var result [][]byte
+
+	for _, item := range input {
+		// Use bytes.Buffer to convert byte slice to string
+		key := string(item)
+		if _, exists := uniqueMap[key]; !exists {
+			uniqueMap[key] = struct{}{}
+			result = append(result, item)
+		}
+	}
+
+	return result
+}