详解Redis内部数据结构——Dict

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

typedef struct dictht {    dictEntry **table;    unsigned long size; //  hashtable 容量    unsigned long sizemask;  // size -1    unsigned long used;  // hashtable 元素个数   used / size =1} dictht;

typedef struct dict {    dictType *type;    void *privdata;    dictht ht[2];// ht[0] , ht[1] =null    long rehashidx; /* rehashing not in progress if rehashidx == -1 */    unsigned long iterators; /* number of iterators currently running */} dict;

// 服务器定时任务void databaseCron() {    ...    if (server.activerehashing) {        for (j = 0; j < dbs_per_call; j++) {            int work_done = incrementallyRehash(rehash_db);            if (work_done) {                /* If the function did some work, stop here, we'll do                 * more at the next cron loop. */                break;            } else {                /* If this db didn't need rehash, we'll try the next one. */                rehash_db++;                rehash_db %= server.dbnum;            }        }    }}

/* Expand the hash table if needed */static int _dictExpandIfNeeded(dict *d){    /* Incremental rehashing already in progress. Return. */    if (dictIsRehashing(d)) return DICT_OK;

    /* If the hash table is empty expand it to the initial size. */    if (d->ht[0].size == 0) return dictExpand(d, DICT_HT_INITIAL_SIZE);

    /* 元素个数大于等于数组长度&&（能扩容(bgsave时尽量不扩容)或元素大于5倍时强制扩容）   * static unsigned int dict_force_resize_ratio = 5;   */    if (d->ht[0].used >= d->ht[0].size &&        (dict_can_resize ||         d->ht[0].used/d->ht[0].size > dict_force_resize_ratio))    {        return dictExpand(d, d->ht[0].used*2);    }    return DICT_OK;}