mongodb查找的性能非常慢

Question

我是nodejs和mongodb的新手。为了验证这一点，我从#奥斯卡网站上获得了2.50万条推文。现在我正在处理数据，但是像下面这样的查询非常慢.(最多40秒)(我直接在控制台上执行查询)

db.oscars.find({user.screen_name: "monxas"})

我做错了什么吗？是否存在加速查询的方法？

tweets具有这种结构，如果这有帮助的话：

 {
  "_id" : ObjectId("54ea1f0f5fbae7a02067024b"),
  "created_at" : "Sun Feb 22 18:25:20 +0000 2015",
  "id" : 5.6956360590721434E+17,
  "id_str" : "569563605907214338",
  "text" : "#Oscars2015 Who will win tonight? All hopes are on you guys.",
  "source" : "<a href=\"http://twitter.com/#!/download/ipad\" rel=\"nofollow\">Twitter for iPad</a>",
  "truncated" : false,
  "in_reply_to_status_id" : null,
  "in_reply_to_status_id_str" : null,
  "in_reply_to_user_id" : null,
  "in_reply_to_user_id_str" : null,
  "in_reply_to_screen_name" : null,
  "user" : {
    "id" : 2596742425.0,
    "id_str" : "2596742425",
    "name" : "jclivesforever26",
    "screen_name" : "jacuasay092600",
    "location" : "",
    "url" : null,
    "description" : "Da Bulls!!! Ed Sheeran is life!!!",
    "protected" : false,
    "verified" : false,
    "followers_count" : 21,
    "friends_count" : 183,
    "listed_count" : 0,
    "favourites_count" : 78,
    "statuses_count" : 283,
    "created_at" : "Mon Jun 30 18:13:13 +0000 2014",
    "utc_offset" : null,
    "time_zone" : null,
    "geo_enabled" : true,
    "lang" : "en",
    "contributors_enabled" : false,
    "is_translator" : false,
    "profile_background_color" : "C0DEED",
    "profile_background_image_url" : "http://abs.twimg.com/images/themes/theme1/bg.png",
    "profile_background_image_url_https" : "https://abs.twimg.com/images/themes/theme1/bg.png",
    "profile_background_tile" : false,
    "profile_link_color" : "0084B4",
    "profile_sidebar_border_color" : "C0DEED",
    "profile_sidebar_fill_color" : "DDEEF6",
    "profile_text_color" : "333333",
    "profile_use_background_image" : true,
    "profile_image_url" : "http://pbs.twimg.com/profile_images/542805253952135168/Ttwm541P_normal.jpeg",
    "profile_image_url_https" : "https://pbs.twimg.com/profile_images/542805253952135168/Ttwm541P_normal.jpeg",
    "profile_banner_url" : "https://pbs.twimg.com/profile_banners/2596742425/1421468064",
    "default_profile" : true,
    "default_profile_image" : false,
    "following" : null,
    "follow_request_sent" : null,
    "notifications" : null
  },
  "geo" : null,
  "coordinates" : null,
  "place" : null,
  "contributors" : null,
  "retweet_count" : 0,
  "favorite_count" : 0,
  "entities" : {
    "hashtags" : [{
        "text" : "Oscars2015",
        "indices" : [0, 11]
      }],
    "trends" : [],
    "urls" : [],
    "user_mentions" : [],
    "symbols" : []
  },
  "favorited" : false,
  "retweeted" : false,
  "possibly_sensitive" : false,
  "filter_level" : "low",
  "lang" : "en",
  "timestamp_ms" : "1424629520285"
}

Answer 1

使用explain游标方法查找有关查询计划的更多信息

db.oscars.find({user.screen_name: "monxas"}).explain();

如果没有定义索引，则可以在user.screen_name上添加索引，以使用ensureIndex加快查询速度，如下所示

db.oscars.ensureIndex({"user.screen_name": 1});