对MongoDB中

Question

字典键我有文章的集合MongoDB中具有以下结构过滤文件：

{ 
    'category': 'Legislature', 
    'updated': datetime.datetime(2010, 3, 19, 15, 32, 22, 107000), 
    'byline': None, 
    'tags': { 
     'party': ['Peter Hoekstra', 'Virg Bernero', 'Alma Smith', 'Mike Bouchard', 'Tom George', 'Rick Snyder'], 
     'geography': ['Michigan', 'United States', 'North America'] 
    }, 
    'headline': '2 Mich. gubernatorial candidates speak to students', 
    'text': [ 
     'BEVERLY HILLS, Mich. (AP) \u2014 Two Democratic and Republican gubernatorial candidates found common ground while speaking to private school students in suburban Detroit', 
     "Democratic House Speaker state Rep. Andy Dillon and Republican U.S. Rep. Pete Hoekstra said Friday a more business-friendly government can help reduce Michigan's nation-leading unemployment rate.", 
     "The candidates were invited to Detroit Country Day Upper School in Beverly Hills to offer ideas for Michigan's future.", 
     'Besides Dillon, the Democratic field includes Lansing Mayor Virg Bernero and state Rep. Alma Wheeler Smith. Other Republicans running are Oakland County Sheriff Mike Bouchard, Attorney General Mike Cox, state Sen. Tom George and Ann Arbor business leader Rick Snyder.', 
     'Former Republican U.S. Rep. Joe Schwarz is considering running as an independent.' 
    ], 
    'dateline': 'BEVERLY HILLS, Mich.', 
    'published': datetime.datetime(2010, 3, 19, 8, 0, 31), 
    'keywords': "Governor's Race", 
    '_id': ObjectId('4ba39721e0e16cb25fadbb40'), 
    'article_id': 'urn:publicid:ap.org:0611e36fb084458aa620c0187999db7e', 
    'slug': "BC-MI--Governor's Race,2nd Ld-Writethr" 
} 

如果我想写的是寻找那些至少有1地理学所有文章查询标签，我该怎么做？我曾尝试编写db.articles.find（{'tags'：'geography'}），但这似乎不起作用。我也想过将搜索参数改为'tags.geography'，但是我有一段时间的魔力来搞清楚搜索谓词是什么。

Answer 1

如果当没有在它（即，当你添加一个位置它的创建）的任何标签的“地理”字段不存在，你可以这样做：

db.articles.find({tags.geography : {$exists : true}}) 

如果它确实存在并且是空的（即"geography" : []），你应该添加一个geography_size场或某事做：

db.articles.find({tags.geography_size : {$gte : 1}}) 

有在http://www.mongodb.org/display/DOCS/Advanced+Queries