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Redis源码剖析之数据库结构

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以下涉及到的源码均为redis5.0-rc3版本的代码【点击查看官方源码】

Redis服务器初始化数据库的个数为16个，由server.h头文件中的宏定义而来，如下所示：

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#define CONFIG_DEFAULT_DBNUM     16

并且每个数据库的结构都有一个redisDb构成，如下是redisDb的数据结构定义（server.h头文件中），各字段的含义可见上面的源码注释：

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/* 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 */
    list *defrag_later;         /* List of key names to attempt to defrag one by one, gradually. */
} redisDb;