Redis常用数据类型及其存储结构(源码篇)

typedef char *sds;      //注意，sds其实不是一个结构体类型，而是被typedef的char*

struct sdshdr {
    unsigned int len;   //buf中已经使用的长度
    unsigned int free;  //buf中未使用的长度
    char buf[];         //柔性数组buf
};

typedef char *sds;      

struct __attribute__ ((__packed__)) sdshdr5 {     // 对应的字符串长度小于 1<<5
    unsigned char flags; 
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr8 {     // 对应的字符串长度小于 1<<8
    uint8_t len; /* used */                       // 目前字符创的长度,使用1个byte
    uint8_t alloc;                                // 已经分配的总长度,使用1个byte
    unsigned char flags;                          // flag用3bit来标明类型，类型后续解释，其余5bit目前没有使用。使用1byte。
    char buf[];                                   // 柔性数组，以''结尾
};
struct __attribute__ ((__packed__)) sdshdr16 {    // 对应的字符串长度小于 1<<16
    uint16_t len; /* used，使用2byte */
    uint16_t alloc; /* excluding the header and null terminator,使用2byte */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr32 {    // 对应的字符串长度小于 1<<32
    uint32_t len; /* used,使用4byte */
    uint32_t alloc; /* excluding the header and null terminator,使用4byte */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};
struct __attribute__ ((__packed__)) sdshdr64 {    // 对应的字符串长度小于 1<<64
    uint64_t len; /* used */
    uint64_t alloc; /* excluding the header and null terminator */
    unsigned char flags; /* 3 lsb of type, 5 unused bits */
    char buf[];
};

struct redisServer {
    /* General */
    pid_t pid;                  /* Main process pid. */    
    ......  
    int hz;                     /* serverCron() calls frequency in hertz */
    redisDb *db;
    dict *commands;             /* Command table */
    dict *orig_commands;        /* Command table before command renaming. */
    aeEventLoop *el; 
    ...... 
    char runid[CONFIG_RUN_ID_SIZE+1];  /* ID always different at every exec. */ 
    ...... 
    list *clients;              /* List of active clients */
    list *clients_to_close;     /* Clients to close asynchronously */
    list *clients_pending_write; /* There is to write or install handler. */
    list *clients_pending_read;  /* Client has pending read socket buffers. */
    list *slaves, *monitors;    /* List of slaves and MONITORs */
    client *current_client;     /* Current client executing the command. */
    ......
};

typedef struct redisDb {
    dict *dict;                 /* 键值对字典，保存数据库中所有的键值对 */
    dict *expires;              /* 过期字典，保存着设置过期的键和键的过期时间*/
    dict *blocking_keys;        /*保存着 所有造成客户端阻塞的键和被阻塞的客户端 (BLPOP) */
    dict *ready_keys;           /* 保存着 处于阻塞状态的键，value为NULL*/
    dict *watched_keys;         /* 事物模块，用于保存被WATCH命令所监控的键 */
    　　　　// 当内存不足时，Redis会根据LRU算法回收一部分键所占的空间，而该eviction_pool是一个长为16数组，保存可能被回收的键
    　　　　// eviction_pool中所有键按照idle空转时间，从小到大排序，每次回收空转时间最长的键
    struct evictionPoolEntry *eviction_pool;    /* Eviction pool of keys */
    int id;                     /* 数据库ID */
    long long avg_ttl;          /* 键的平均过期时间 */
} redisDb;

typedef struct dict {
    dictType *type;
    void *privdata;
    dictht ht[2]; //方便渐进的rehash扩容，dict的hashtable
    long rehashidx; /* rehashing not in progress if rehashidx == -1 */
    unsigned long iterators; /* number of iterators currently running */
} dict;

typedef struct dictht {
    dictEntry **table;
    unsigned long size;
    unsigned long sizemask;
    unsigned long used;
} dictht;

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

typedef struct redisObject {
    unsigned type:4;       //占用4bit
    unsigned encoding:4;   //占用4bit
    unsigned lru:LRU_BITS; /*占用24bit LRU time (relative to global lru_clock) or
                            * LFU data (least significant 8 bits frequency
                            * and most significant 16 bits access time). */
    int refcount;          //占用4byte
    void *ptr;             //占用8byte  总空间:4bit+4bit+24bit+4byte+8byte = 16byte
} robj;

/* The actual Redis Object */
#define OBJ_STRING 0    /* String object. */
#define OBJ_LIST 1      /* List object. */
#define OBJ_SET 2       /* Set object. */
#define OBJ_ZSET 3      /* Sorted set object. */
#define OBJ_HASH 4      /* Hash object. */

#define OBJ_MODULE 5    /* Module object. */
#define OBJ_STREAM 6    /* Stream object. */

#define OBJ_ENCODING_RAW 0     /* Raw representation */
#define OBJ_ENCODING_INT 1     /* Encoded as integer */
#define OBJ_ENCODING_HT 2      /* Encoded as hash table */
#define OBJ_ENCODING_ZIPMAP 3  /* Encoded as zipmap */
#define OBJ_ENCODING_LINKEDLIST 4 /* No longer used: old list encoding. */
#define OBJ_ENCODING_ZIPLIST 5 /* Encoded as ziplist */
#define OBJ_ENCODING_INTSET 6  /* Encoded as intset */
#define OBJ_ENCODING_SKIPLIST 7  /* Encoded as skiplist */
#define OBJ_ENCODING_EMBSTR 8  /* Embedded sds string encoding */
#define OBJ_ENCODING_QUICKLIST 9 /* Encoded as linked list of ziplists */
#define OBJ_ENCODING_STREAM 10 /* Encoded as a radix tree of listpacks */

#string类型查看redis的存储
SET key value                               //存入字符串键值对
STRLEN key                                  //查看key的长度(占用的byte字节)
OBJECT ENCODING key                         //查看key在redis中的存储类型
SETRANGE key offset value                   //修改key从offset(字符偏移量)字符修改为value，如果原本为embstr修改后也会变成raw。
GETRANGE key start end                      //获取key的部分值

list-max-ziplist-size -2                    //单个ziplist节点最大能存储8kb，超过则进行分裂，将数据存储在新的ziplist节点中
list-compress-depth   0                     //0代表所有节点，都不进行压缩。1，代表从头节点往后走一个，尾部节点往前走一个不用压缩，其他的全部压缩。

typedef struct intset {
    uint32_t encoding;   //编码类型
    uint32_t length;       //元素个数
    int8_t contents[];     //元素数据
} intset;

//redis中保存整型的编码类型有int16_t,int32_t,int64_t
#define INTSET_ENC_INT16(sizeof(int16_t))
#define INTSET_ENC_INT32(sizeof(int32_t))
#define INTSET_ENC_INT64(sizeof(int64_t))

HMSET key f1 v1 f2 v2 f3 v3                 //在一个哈希表key中存储多个键值对
OBJECT ENCODING key                         //查看key在redis中的存储类型为ziplist
HGETALL key                                 //查看key对应的所有field和value发现为有序的
HSET key f4 x...x                           //在一个哈希表key中存储一个长度超过64的value
HSTRLEN key f4                              //查看key中field为f4的长度
OBJECT ENCODING key                         //查看key在redis中的存储类型为hashtable
HGETALL key                                 //查看key对应的所有field和value发现为无序