Function slotToKeyUpdateKey

app/redis-6.2.6/src/db.c:1916–1933

Slot to Key API. This is used by Redis Cluster in order to obtain in * a fast way a key that belongs to a specified hash slot. This is useful * while rehashing the cluster and in other conditions when we need to * understand if we have keys for a given hash slot. */

 * while rehashing the cluster and in other conditions when we need to
 * understand if we have keys for a given hash slot. */
void slotToKeyUpdateKey(sds key, int add) {
    size_t keylen = sdslen(key);
    unsigned int hashslot = keyHashSlot(key,keylen);
    unsigned char buf[64];
    unsigned char *indexed = buf;

    server.cluster->slots_keys_count[hashslot] += add ? 1 : -1;
    if (keylen+2 > 64) indexed = zmalloc(keylen+2);
    indexed[0] = (hashslot >> 8) & 0xff;
    indexed[1] = hashslot & 0xff;
    memcpy(indexed+2,key,keylen);
    if (add) {
        raxInsert(server.cluster->slots_to_keys,indexed,keylen+2,NULL,NULL);
    } else {
        raxRemove(server.cluster->slots_to_keys,indexed,keylen+2,NULL);
    }
    if (indexed != buf) zfree(indexed);
}

void slotToKeyAdd(sds key) {
    slotToKeyUpdateKey(key,1);