mongoDB中批量修改字段

// 為每一個文章文檔新增一個image_count字段，用於記錄此文章包含的圖片個數
db['test.articles'].find({'title':'wfc test'}).forEach( function(thisArticle){
    // 這里要強制轉為整形，否則會變成浮點數
    // 要用NumberInt轉換為整形，用parseInt得到依然是浮點數
    imageCount = NumberInt( thisArticle['article_images'].length )
    db['test.articles'].update({'_id':thisArticle['_id']}, {$set:{'image_count':imageCount}} )
   })

// 比較精簡干練的寫法
db.test.articles.find({'title':'wfc test'}).forEach( function(thisArticle){
    thisArticle.image_count = NumberInt( thisArticle.article_images.length )
    db.test.articles.save(thisArticle)
  })

// 將文檔的字段放入嵌套數組后，再刪除該字段(數據結構修改)    
db['test.game'].find({'article_image':{$exists:0}}).forEach( function(thisArticle){
    articleImage = {'remote':thisArticle.game_icon, 'local':thisArticle.game_local_icon,
                    'original':thisArticle.game_remote_icon, 'upload':thisArticle.icon_upload}
    thisArticle.image_upload = thisArticle.icon_upload
    thisArticle.modify_time = thisArticle.spider_time
    thisArticle.article_image = []
    thisArticle.article_image.push(articleImage)
    delete thisArticle.game_icon
    delete thisArticle.game_local_icon
    delete thisArticle.game_remote_icon
    delete thisArticle.icon_upload
    db['test.game'].save(thisArticle)
})

// 按名稱分組統計
db['test.articles'].group({
    key:{'name':1},
    condition:{'name':{$exists:1}},
    $reduce:function(curr, result) {
        result.total += 1
    },
    initial:{total:0},
})