Function moduleCreateEmptyKey

app/redis-6.2.6/src/module.c:537–565

Create an empty key of the specified type. `key` must point to a key object * opened for writing where the `.value` member is set to NULL because the * key was found to be non existing. * * On success REDISMODULE_OK is returned and the key is populated with * the value of the specified type. The function fails and returns * REDISMODULE_ERR if: * * 1. The key is not open for writing. * 2.

 * 3. The specified type is unknown.
 */
int moduleCreateEmptyKey(RedisModuleKey *key, int type) {
    robj *obj;

    /* The key must be open for writing and non existing to proceed. */
    if (!(key->mode & REDISMODULE_WRITE) || key->value)
        return REDISMODULE_ERR;

    switch(type) {
    case REDISMODULE_KEYTYPE_LIST:
        obj = createQuicklistObject();
        quicklistSetOptions(obj->ptr, server.list_max_ziplist_size,
                            server.list_compress_depth);
        break;
    case REDISMODULE_KEYTYPE_ZSET:
        obj = createZsetZiplistObject();
        break;
    case REDISMODULE_KEYTYPE_HASH:
        obj = createHashObject();
        break;
    case REDISMODULE_KEYTYPE_STREAM:
        obj = createStreamObject();
        break;
    default: return REDISMODULE_ERR;
    }
    dbAdd(key->db,key->key,obj);
    key->value = obj;
    moduleInitKeyTypeSpecific(key);
    return REDISMODULE_OK;
}

/* This function is called in low-level API implementation functions in order
 * to check if the value associated with the key remained empty after an