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这篇文章主要讲解了“redis的scan语法及作用对象”,文中的讲解内容简单清晰,易于学习与理解,下面请大家跟着小编的思路慢慢深入,一起来研究和学习“redis的scan语法及作用对象”吧!
在redis的db存在大量key或者db里头的某个set、zset、hash里头的元素非常多的话,用普通的get all操作很可能导致redis因为这个操作阻塞了,导致不能响应其他操作,特别是在高并发、海量数据的背景下,这个问题显得尤其严重。那么能不能像数据库那样有个分页的功能呢,答案就是scan操作。本文主要展示怎么在redis-cli以及SpringDataRedis中的使用。【推荐:redis视频教程】
scan之后返回两部分,第一部分是下次scan的参数,第二部分就是scan出来的项
db(key
)
127.0.0.1:6379> scan 0 1) "120" 2) 1) "articleMap:63" 2) "articleMap:37" 3) "counter:__rand_int__" 4) "articleMap:60" 5) "tagSet:tag5" 6) "articleMap:80" 7) "messageCache~keys" 8) "mymap" 9) "articleMap:46" 10) "articleMap:55" 127.0.0.1:6379> scan 120 1) "28" 2) 1) "articleMap:17" 2) "tagSet:tag1" 3) "articleMap:18" 4) "articleMap:81" 5) "\xac\xed\x00\x05t\x00\btest-cas" 6) "articleMap:51" 7) "articleMap:94" 8) "articleMap:26" 9) "articleMap:71" 10) "user-abcde"
set(value
)
127.0.0.1:6379> sscan myset 0 1) "3" 2) 1) "m" 2) "j" 3) "c" 4) "h" 5) "f" 6) "i" 7) "a" 8) "g" 9) "n" 10) "e" 11) "b" 127.0.0.1:6379> sscan myset 3 1) "0" 2) 1) "l" 2) "k" 3) "d"
zset(value & score
)
127.0.0.1:6379> zscan sortset 0 1) "0" 2) 1) "tom" 2) "89" 3) "jim" 4) "90" 5) "david" 6) "100"
hash(key & value
)
127.0.0.1:6379> hscan mymap 0 1) "0" 2) 1) "name" 2) "codecraft" 3) "email" 4) "pt@g.cn" 5) "age" 6) "20" 7) "desc" 8) "hello" 9) "sex" 10) "male"
count(指定每次取多少条
)
127.0.0.1:6379> scan 0 count 5 1) "240" 2) 1) "articleMap:63" 2) "articleMap:37" 3) "counter:__rand_int__" 4) "articleMap:60" 5) "tagSet:tag5"
match(匹配key
)
127.0.0.1:6379> scan 0 match article* 1) "120" 2) 1) "articleMap:63" 2) "articleMap:37" 3) "articleMap:60" 4) "articleMap:80" 5) "articleMap:46" 6) "articleMap:55"
@Test public void scanDbKeys(){ template.execute(new RedisCallback<Iterable<byte[]>>() { @Override public Iterable<byte[]> doInRedis(RedisConnection connection) throws DataAccessException { List<byte[]> binaryKeys = new ArrayList<byte[]>(); Cursor<byte[]> cursor = connection.scan(ScanOptions.scanOptions().count(5).build()); while (cursor.hasNext()) { byte[] key = cursor.next(); binaryKeys.add(key); System.out.println(new String(key, StandardCharsets.UTF_8)); } try { cursor.close(); } catch (IOException e) { // do something meaningful } return binaryKeys; } }); }
/** * sadd myset a b c d e f g h i j k l m n */ @Test public void scanSet(){ Cursor<String> cursor = template.opsForSet().scan("myset",ScanOptions.NONE); while (cursor.hasNext()){ System.out.println(cursor.next()); } }
/** * zadd sortset 89 tom 90 jim 100 david */ @Test public void scanZSet(){ Cursor<ZSetOperations.TypedTuple<String>> cursor = template.opsForZSet().scan("sortset",ScanOptions.NONE); while (cursor.hasNext()){ ZSetOperations.TypedTuple<String> item = cursor.next(); System.out.println(item.getValue() + ":" + item.getScore()); } }
/** * hset mymap name "codecraft" * hset mymap email "pt@g.cn" * hset mymap age 20 * hset mymap desc "hello" * hset mymap sex "male" */ @Test public void scanHash(){ Cursor<Map.Entry<Object, Object>> curosr = template.opsForHash().scan("mymap", ScanOptions.NONE); while(curosr.hasNext()){ Map.Entry<Object, Object> entry = curosr.next(); System.out.println(entry.getKey()+":"+entry.getValue()); } }
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