Redis 6.0源码学习 RedisObject-CFANZ编程社区

文章目录

Redis 6.0源码学习 RedisObject

数据结构
类型
编码格式

Redis 6.0源码学习 RedisObject

Redis中key和value的类型都是redisObject，可见学习这个类型的重要性。

数据结构

redisObject（见代码片段1）中存储了类型信息、编码格式、lru信息、引用次数和内容指针。

代码片段1 server.h中redisObject相关定义

#define LRU_BITS 24

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;

类型

type属性，表示Redis对象的类型，占用4位，可以表示16种不同的类型，目前包含如下类型。

值	对象类型
0	字符串String
1	列表List
2	集合Set
3	有序集合Sorted set
4	哈希表Hash
5	Module
6	流Stream

代码片段2 server.h中redisObject type相关定义

* A redis object, that is a type able to hold a string / list / set */

/* 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. */

/* The "module" object type is a special one that signals that the object
 * is one directly managed by a Redis module. In this case the value points
 * to a moduleValue struct, which contains the object value (which is only
 * handled by the module itself) and the RedisModuleType struct which lists
 * function pointers in order to serialize, deserialize, AOF-rewrite and
 * free the object.
 *
 * Inside the RDB file, module types are encoded as OBJ_MODULE followed
 * by a 64 bit module type ID, which has a 54 bits module-specific signature
 * in order to dispatch the loading to the right module, plus a 10 bits
 * encoding version. */
#define OBJ_MODULE 5/* Module object. */
#define OBJ_STREAM 6/* Stream object. */

编码格式

encoding属性，表示对象内部存储的编码，在一定条件下，对象的编码可以在多个编码之间转化，长度占用4位，包含如下编码。

encoding	数据结构	可存储对象类型
OBJ_ENCODING_RAW	SDS	字符串
OBJ_ENCODING_INT	整型	字符串
OBJ_ENCODING_HT	哈希表	集合、有序集合、哈希表
OBJ_ENCODING_ZIPMAP	压缩表	未使用
OBJ_ENCODING_LINKEDLIST	链表	不再使用
OBJ_ENCODING_ZIPLIST	压缩列表	哈希表、有序集合
OBJ_ENCODING_INTSET	整型集合	集合
OBJ_ENCODING_SKIPLIST	跳表	有序集合
OBJ_ENCODING_EMBSTR	sds	字符串
OBJ_ENCODING_QUICKLIST	整型	列表
OBJ_ENCODING_STREAM	stream	stream

代码片段3 server.h中redisObject encoding相关定义

#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 */