Redis初学者学习：字典（图）及其基本编码结构

redis是用C编写的，但是C语言没有字典数据结构，所以C语言本身使用字典结构来定义结构typedef Redis数据库结构体

/* Redis database representation. There are multiple databases identified
 * by integers from 0 (the default database) up to the max configured
 * database. The database number is the 'id' field in the structure. */
typedef struct redisDb {
    dict *dict;                 /* The keyspace for this DB */
    dict *expires;              /* Timeout of keys with a timeout set */
    dict *blocking_keys;        /* Keys with clients waiting for data (BLPOP)*/
    dict *ready_keys;           /* Blocked keys that received a PUSH */
    dict *watched_keys;         /* WATCHED keys for MULTI/EXEC CAS */
    int id;                     /* Database ID */
    long long avg_ttl;          /* Average TTL, just for stats */
    unsigned long expires_cursor; /* Cursor of the active expire cycle. */
    list *defrag_later;         /* List of key names to attempt to defrag one by one, gradually. */
} redisDb;

redisDb 在结构体 redisDb

src\server.h 中存储了 redis 数据库的底层数据结构：

• dict

  typedef struct dictEntry {
      void *key;
      union {
          void *val;
          uint64_t u64;
          int64_t s64;
          double d;
      } v;
      struct dictEntry *next;
  } dictEntry;

  dictDi res

过期时间

• 阻止keys

等待数据的客户端密钥 (BLPOP)

• ready_keys

接收 PUSH 的密钥被阻止❙‶监控 Pu❙tin ULTI/EXEC CAS 类似事务

• id

使用数据库 ID , 0-15

• avg_ttl

统计平均ttl

• expires_cursor

expires_cursor过期ter

内存按键列表

typedef struct dict

src\dict.h 字典数据结构字典数据结构存储

• type❙typedatatypeDi

私有数据

• ht

哈希表、旧表和新表。新表仅在哈希表扩展时使用，即ht[1]

typedef struct dictType

typedef struct dictType {
    uint64_t (*hashFunction)(const void *key);
    void *(*keyDup)(void *privdata, const void *key);
    void *(*valDup)(void *privdata, const void *obj);
    int (*keyCompare)(void *privdata, const void *key1, const void *key2);
    void (*keyDestructor)(void *privdata, void *key);
    void (*valDestructor)(void *privdata, void *obj);
    int (*expandAllowed)(size_t moreMem, double usedRatio);
} dictType;

dictType定义了多个函数指针，方便后续方法实现和调用。 比如函数指针keyCompare，它是一个指向函数的指针。该函数有 3 个参数和 1 个返回值：

3 个参数

• privdata

具体数据 key1

key1 该键的具体值 key2 该键的具体值

功能它点此 keyCompare 指示器用于比较两个键的大小。容量

哈希表

• sizemask

等于大小 -1

• used

可哈希元素数量

127.0.0.1:6379> set test 99999999991111111111222222222233333333334444
OK
127.0.0.1:6379> OBJECT encoding test
"embstr"
127.0.0.1:6379> STRLEN test
(integer) 44

可哈希元素数量

127.0.0.1:6379> set test 99999999991111111111222222222233333333334444
OK
127.0.0.1:6379> OBJECT encoding test
"embstr"
127.0.0.1:6379> STRLEN test
(integer) 44

可哈希元素数量

127.0.0.1:6379> set test 99999999991111111111222222222233333333334444
OK
127.0.0.1:6379> OBJECT encoding test
"embstr"
127.0.0.1:6379> STRLEN test
(integer) 44

可散列元素的数量

127.0.0.1:6379> set test 99999999991111111111222222222233333333334444
OK
127.0.0.1:6379> OBJECT encoding test
"embstr"
127.0.0.1:6379> STRLEN test
(integer) 44

可哈希的元素数量 Enstruct try是一个真实的键值对数据结构

• key

键值实际上是类型为的sds

typedef struct dictEntry {
    void *key;
    union {
        void *val;
        uint64_t u64;
        int64_t s64;
        double d;
    } v;
    struct dictEntry *next;
} dictEntry;

v vv

value dikt试试

typedef struct redisObject {
    unsigned type:4;
    unsigned encoding:4;
    unsigned lru:LRU_BITS; /* LRU time (relative to global lru_clock) or
                            * LFU data (least significant 8 bits frequency
                            * and most significant 16 bits access time). */
    int refcount;
    void *ptr;
} robj;

127.0.0.1:6379> SETBIT login:9:11 25 1
(integer) 0
127.0.0.1:6379> SETBIT login:9:11 26 1
(integer) 0
127.0.0.1:6379> SETBIT login:9:11 27 1
(integer) 0
127.0.0.1:6379> BITCOUNT login:9:11
(integer) 3
127.0.0.1:6379> strlen login:9:11
(integer) 4

127.0.0.1:6379> BITOP or login:or login:9:11 login:9:12
(integer) 4
127.0.0.1:6379> BITCOUNT login:or
(integer) 3

127.0.0.1:6379> type login:or
string
127.0.0.1:6379> OBJECT encoding login:or
"raw"
127.0.0.1:6379> OBJECT encoding login:9:12
"raw"
127.0.0.1:6379> OBJECT encoding login:and
"raw"

127.0.0.1:6379> set name xiaoming
OK
127.0.0.1:6379> OBJECT encoding name
"embstr"