fix(redis): 避免 Redis 搜索因稀疏 SCAN MATCH 返回空结果 (#746)

fixes #738

Redis SCAN MATCH 可能连续返回空批次，但后续 cursor 页仍然存在匹配 key。
此前搜索模式最多扫描 16 轮，可能导致首次点击搜索无数据，而点击“加载更多”后才出现结果。

移除搜索模式的固定轮数限制，改由已有的搜索时间上限和目标数量限制兜底。
新增回归测试，验证搜索可以继续越过 16 个空匹配页并返回后续结果。

internal/redis/redis_impl.go

@@ -47,7 +47,6 @@ const (
 	redisScanMaxDuration              = 12 * time.Second
 	redisSearchMaxTargetCount   int64 = 1000
 	redisSearchMaxStepCount     int64 = 1000
-	redisSearchMaxRounds              = 16
 	redisSearchMaxDuration            = 3 * time.Second
 )
 
@@ -552,7 +551,9 @@ func (r *RedisClientImpl) ScanKeys(pattern string, cursor uint64, count int64) (
 		if scanStepCount > redisSearchMaxStepCount {
 			scanStepCount = redisSearchMaxStepCount
 		}
-		maxRounds = redisSearchMaxRounds
+		// SCAN MATCH 可能连续返回空批次，但后续 cursor 页仍然存在匹配 key。
+		// 搜索模式不使用固定轮数限制，改由 maxDuration 和 targetCount 兜底。
+		maxRounds = 0
 		maxDuration = redisSearchMaxDuration
 	}
 
@@ -604,7 +605,7 @@ func (r *RedisClientImpl) ScanKeys(pattern string, cursor uint64, count int64) (
 
 				nodeCursor = nextCursor
 				round++
-				if nodeCursor == 0 || round >= maxRounds {
+				if nodeCursor == 0 || (maxRounds > 0 && round >= maxRounds) {
 					break
 				}
 			}
@@ -653,7 +654,7 @@ func (r *RedisClientImpl) ScanKeys(pattern string, cursor uint64, count int64) (
 
 		currentCursor = nextCursor
 		round++
-		if currentCursor == 0 || round >= maxRounds {
+		if currentCursor == 0 || (maxRounds > 0 && round >= maxRounds) {
 			break
 		}
 	}

internal/redis/redis_impl_test.go

@@ -14,6 +14,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"testing"
 	goredis "github.com/redis/go-redis/v9"
 )
@@ -741,6 +742,81 @@ func TestListRemoveUsesLRemForOneMatchingValue(t *testing.T) {
 	t.Fatalf("expected LREM command, got %v", commands)
 }
 
+func TestRedisSearchScanContinuesPastEmptyMatchedPages(t *testing.T) {
+	var mu sync.Mutex
+	scanCalls := 0
+	const searchPattern = "*[lL][aA][tT][eE]*"
+
+	redisScanResponse := func(cursor string, keys ...string) string {
+		var builder strings.Builder
+		builder.WriteString("*2\r\n")
+		builder.WriteString(redisBulkString(cursor))
+		builder.WriteString(fmt.Sprintf("*%d\r\n", len(keys)))
+		for _, key := range keys {
+			builder.WriteString(redisBulkString(key))
+		}
+		return builder.String()
+	}
+
+	addr := startRedisProtocolTestServer(t, func(args []string) string {
+		command := strings.ToUpper(strings.TrimSpace(args[0]))
+		switch command {
+		case "HELLO":
+			return "-ERR unknown command 'HELLO'\r\n"
+		case "CLIENT":
+			return "-ERR unknown subcommand\r\n"
+		case "SCAN":
+			mu.Lock()
+			defer mu.Unlock()
+			scanCalls++
+			for i := 0; i+1 < len(args); i++ {
+				if strings.EqualFold(args[i], "MATCH") && args[i+1] != searchPattern {
+					t.Fatalf("expected SCAN MATCH %q, got command %v", searchPattern, args)
+				}
+			}
+			if scanCalls <= 16 {
+				return redisScanResponse(strconv.Itoa(scanCalls))
+			}
+			return redisScanResponse("0", "late:user:1")
+		case "TYPE":
+			return "+string\r\n"
+		case "TTL":
+			return ":-1\r\n"
+		}
+		return "+OK\r\n"
+	})
+
+	rawClient := goredis.NewClient(&goredis.Options{
+		Addr:     addr,
+		Protocol: 2,
+	})
+	client := &RedisClientImpl{
+		client:       rawClient,
+		singleClient: rawClient,
+	}
+	defer client.Close()
+
+	result, err := client.ScanKeys(searchPattern, 0, 10)
+	if err != nil {
+		t.Fatalf("ScanKeys returned error: %v", err)
+	}
+	if result == nil || len(result.Keys) != 1 {
+		t.Fatalf("expected one searched key after empty pages, got %#v", result)
+	}
+	if result.Keys[0].Key != "late:user:1" {
+		t.Fatalf("expected late:user:1, got %#v", result.Keys[0])
+	}
+	if result.Cursor != "0" {
+		t.Fatalf("expected completed cursor, got %q", result.Cursor)
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+	if scanCalls <= 16 {
+		t.Fatalf("expected ScanKeys to continue past 16 empty search pages, got %d calls", scanCalls)
+	}
+}
+
 func TestRedisSelectDBReconnectsWithSentinelConfig(t *testing.T) {
 	oldConnect := redisDBSwitchConnect
 	defer func() {