如何在DynamoDB (iOS)中查询多个项目

Question

我想获得许多videoid的项目，而不是像在这个代码中只有一个视频项目?是否有一种方法来查询多个项目从一个索引?

AWSDynamoDBObjectMapper *objectMapper = [AWSDynamoDBObjectMapper defaultDynamoDBObjectMapper];
AWSDynamoDBQueryExpression *queryExpression = [AWSDynamoDBQueryExpression new];
queryExpression.indexName = @"getVideoItem";
queryExpression.keyConditionExpression = @"#id = :id";
queryExpression.expressionAttributeNames = @{
                                             @"#id" : @"id",
                                             };
queryExpression.expressionAttributeValues = @{
                                              @":id" : videoId,
                                              };
__weak typeof(self) weakSelf = self;
[objectMapper query:[PublicVideos class]
         expression:queryExpression
  completionHandler:^(AWSDynamoDBPaginatedOutput * _Nullable response, NSError * _Nullable error) {
      if (!error) {
          dispatch_async(dispatch_get_main_queue(), ^{
              if ([weakSelf.delegate respondsToSelector:@selector(ServerConnectionHandlerVideoListRecevied:)]) {
                  [weakSelf.delegate ServerConnectionHandlerVideoListRecevied:response.items];
              }
          });
      }
  }];

Answer 1

表的模式是什么样子的?是否为表启用了散列键和范围键?如果您没有任何范围键，那么每个哈希键将只有一个条目，并且您的查询将只返回一行。

如果你同时有哈希键和范围键，你可以这样查询:

AWSDynamoDBObjectMapper *objectMapper = [AWSDynamoDBObjectMapper defaultDynamoDBObjectMapper];
AWSDynamoDBQueryExpression *queryExpression = [AWSDynamoDBQueryExpression new];
queryExpression.indexName = @"Artist-Album-index";
queryExpression.keyConditionExpression = @"#artist = :artist AND #album < :album";
queryExpression.expressionAttributeNames = @{
                                                 @"#artist" : @"Artist",
                                                 @"#album" : @"Album",
                                                 };
queryExpression.expressionAttributeValues = @{
                                                  @":artist" : @"valuetosearch",
                                                  @":album" : @"valuetosearch",
                                                  };
[objectMapper query:[Song class]
             expression:queryExpression
      completionHandler:^(AWSDynamoDBPaginatedOutput * _Nullable response, NSError * _Nullable error) {
          dispatch_async(dispatch_get_main_queue(), ^{
              // handle response
          });
      }];

在上面的代码片段中，它尝试查找符合条件'<'