Redis內存存储结构分析.docxVIP

Redis内存存储结构分析转自：/2011/05/redis-storage.html?Redis: A persistent key-value database with built-in net interface written in ANSI-C for Posix systems1 Redis 内存存储结构 本文是基于 Redis-v2.2.4 版本进行分析.1.1 Redis 内存存储总体结构 Redis 是支持多key-value数据库(表)的,并用 RedisDb 来表示一个key-value数据库(表). redisServer 中有一个 redisDb *db; 成员变量, RedisServer 在初始化时,会根据配置文件的 db 数量来创建一个 redisDb 数组. 客户端在连接后,通过 SELECT 指令来选择一个 reidsDb,如果不指定,则缺省是redisDb数组的第1个(即下标是 0 ) redisDb. 一个客户端在选择 redisDb 后,其后续操作都是在此 redisDb 上进行的. 下面会详细介绍一下 redisDb 的内存结构.redis 的内存存储结构示意图redisDb 的定义:12345678910111213141516171819typedefstructredisDb?{?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 *io_keys;????????????? /* Keys with clients waiting for VM I/O */?dict *watched_keys;???????? /* WATCHED keys for MULTI/EXEC CAS */?intid;?} redisDb;?structredisDb 中 ,dict 成员是与实际存储数据相关的. dict 的定义如下:123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263typedefstructdictEntry?{?void*key;?void*val;?structdictEntry *next;?} dictEntry;?typedefstructdictType?{?unsigned int(*hashFunction)(constvoid*key);?void*(*keyDup)(void*privdata, constvoid*key);?void*(*valDup)(void*privdata, constvoid*obj);?int(*keyCompare)(void*privdata, constvoid*key1, constvoid*key2);?void(*keyDestructor)(void*privdata, void*key);?void(*valDestructor)(void*privdata, void*obj);?} dictType;?/* This is our hash table structure. Every dictionary has two of this as we?* implement incremental rehashing, for the old to the new table. */?typedefstructdictht?{?dictEntry **table;?unsigned longsize;?unsigned longsizemask;?unsigned longused;?} dictht;?typedefstructdict?{?dictType *type;?void*privdata;?dictht ht[2];?intrehashidx; /* rehashing not in progress if rehashidx == -1 */?intiterators; /* number of iterators currently running */?} dict;dict 是主要是由 struct dictht 的 哈唏表构成的, 之所以定义成