[英]Using $push with $group with pymongo
Fix my make_pipeline()
function to, using an aggregation query, count the number of tweets for each user, add them to an array and return the 5 users with the most tweets. 修复我的
make_pipeline()
函数,以使用聚合查询来计算每个用户的tweet数量,将它们添加到数组中,并返回5个具有最高tweets的用户。
Using an aggregation query, count the number of tweets for each user. 使用聚合查询,计算每个用户的推文数量。 In the same
$group
stage, use $push
to accumulate all the tweet texts for each user. 在同一
$group
阶段,使用$push
累积每个用户的所有tweet文本。
Limit your output to the 5 users with the most tweets. 将您的输出限制为鸣叫最多的5个用户。
Your result documents should include only the fields: 您的结果文档应仅包括以下字段:
"_id"
(screen name of user), "_id"
(用户的屏幕名称), "count"
(number of tweets found for the user), "count"
(为用户找到的推文数量), "tweet_texts"
(a list of the tweet texts found for the user). "tweet_texts"
(为用户找到的tweet文本的列表)。 To achieve the previous objective I am testing the following code: 为了实现先前的目标,我正在测试以下代码:
def make_pipeline():
# complete the aggregation pipeline
pipeline = [
{"$group": {"_id": "$user.screen_name", "tweet_texts": {"$push": "$text"}, "count": {"$sum": 1}}},
{"$project": {"_id": "$user.screen_name", "count": 1, "tweet_texts": 1}},
{"$sort" : {"count" : -1}},
{"$limit": 5}
]
return pipeline
First I group all the tweets by username
. 首先,我按
username
名将所有推文分组。 Then, in the same stage, I push all the texted tweets to tweet_texts
and I count each occurrence that was grouped. 然后,在同一阶段,我将所有发短信的推文推送到
tweet_texts
并计算每个分组的事件。 I believe this will give me the number of users with most tweets. 我相信这会给我带来最多推文的用户数量。
Then I make a projection to select only the three fields I want: 然后,我进行投影以仅选择我想要的三个字段:
I finish by sorting and limiting the amount of results. 最后,我对结果进行排序和限制。
I am passing the test, but not the submission. 我通过了考试,但未通过提交。 What am I doing wrong?
我究竟做错了什么? I now the error must be in the first (group) stage, but I can't find for the love of God what I am doing wrong.
我现在的错误一定是在第一个(小组)阶段,但是对于上帝的爱,我找不到我做错了什么。
{
"_id" : ObjectId("5304e2e3cc9e684aa98bef97"),
"text" : "First week of school is over :P",
"in_reply_to_status_id" : null,
"retweet_count" : null,
"contributors" : null,
"created_at" : "Thu Sep 02 18:11:25 +0000 2010",
"geo" : null,
"source" : "web",
"coordinates" : null,
"in_reply_to_screen_name" : null,
"truncated" : false,
"entities" : {
"user_mentions" : [ ],
"urls" : [ ],
"hashtags" : [ ]
},
"retweeted" : false,
"place" : null,
"user" : {
"friends_count" : 145,
"profile_sidebar_fill_color" : "E5507E",
"location" : "Ireland :)",
"verified" : false,
"follow_request_sent" : null,
"favourites_count" : 1,
"profile_sidebar_border_color" : "CC3366",
"profile_image_url" : "http://a1.twimg.com/profile_images/1107778717/phpkHoxzmAM_normal.jpg",
"geo_enabled" : false,
"created_at" : "Sun May 03 19:51:04 +0000 2009",
"description" : "",
"time_zone" : null,
"url" : null,
"screen_name" : "Catherinemull",
"notifications" : null,
"profile_background_color" : "FF6699",
"listed_count" : 77,
"lang" : "en",
"profile_background_image_url" : "http://a3.twimg.com/profile_background_images/138228501/149174881-8cd806890274b828ed56598091c84e71_4c6fd4d8-full.jpg",
"statuses_count" : 2475,
"following" : null,
"profile_text_color" : "362720",
"protected" : false,
"show_all_inline_media" : false,
"profile_background_tile" : true,
"name" : "Catherine Mullane",
"contributors_enabled" : false,
"profile_link_color" : "B40B43",
"followers_count" : 169,
"id" : 37486277,
"profile_use_background_image" : true,
"utc_offset" : null
},
"favorited" : false,
"in_reply_to_user_id" : null,
"id" : NumberLong("22819398300")
}
Please help! 请帮忙!
The $project
step is redundant as the $group
pipeline already produces just those three fields so there's no need for a preceding $project
stage. $project
步骤是多余的,因为$group
管道已经只产生了这三个字段,因此不需要前面的$project
阶段。
The correct pipeline should be 正确的管道应该是
pipeline = [
{
"$group": {
"_id": "$user.screen_name",
"tweet_texts": { "$push": "$text" },
"count": { "$sum": 1 }
}
},
{ "$sort" : { "count" : -1 } },
{ "$limit": 5 }
]
Your $project
pipeline didn't work because the previous $group
pipeline doesn't produce any field "$user.screen_name"
which you attempt to use as the _id
field in the $project
pipeline. 您的
$project
管道不起作用,因为先前的$group
管道不会产生任何字段"$user.screen_name"
,您尝试将其用作$project
管道中的_id
字段。
However, if you wanted to include the $project
step then the working pipeline should follow: 但是,如果要包括
$project
步骤,则工作流程应遵循:
pipeline = [
{
"$group": {
"_id": "$user.screen_name",
"tweet_texts": { "$push": "$text" },
"count": { "$sum": 1 }
}
},
{ "$project": { "count": 1, "tweet_texts": 1 } },
{ "$sort" : { "count" : -1 } },
{ "$limit": 5 }
]
Reading the comments I found out that 阅读评论,我发现
pipeline = [
{"$group": {"_id": "$user.screen_name", "tweet_texts": {"$push": "$text"}, "count": {"$sum": 1}}},
{"$project": {"_id": "$user.screen_name", "count": 1, "tweet_texts": 1}},
{"$sort" : {"count" : -1}},
{"$limit": 5}
]
Should in fact be changed to: 实际上应该更改为:
pipeline = [
{"$group": {"_id": "$user.screen_name", "tweet_texts": {"$push": "$text"}, "count": {"$sum": 1}}},
{"$sort" : {"count" : -1}},
{"$limit": 5}
]
The full answer and explanation can be seen in the answer: 完整的答案和解释可以在答案中看到:
The conclusion of the story is that I am using the $project
stage wrongly. 故事的结论是我错误地使用了
$project
阶段。 Not only was is no needed in the first place, to make it idempotent it should be 首先,不仅不需要,它应该是幂等的。
{"$project": {"_id": "$_id", "count": 1, "tweet_texts": 1}},
I also highly recommend his answer: 我也强烈建议他回答:
The following users deserve kudos++: 以下用户应获得荣誉++:
For directing me in to the right path! 引导我进入正确的道路!
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