mongoDB中批量修改字段
// 为每一个文章文档新增一个image_count字段，用于记录此文章包含的图片个数db['test.articles'].find({'title':'wfc test'}).forEach( function(thisArticle){
// 这里要强制转为整形，否则会变成浮点数
// 要用NumberInt转换为整形，用parseInt得到依然是浮点数
imageCount = NumberInt( thisArticle['article_images'].length )
db['test.articles'].update({'_id':thisArticle['_id']}, {$set:{'image_count':imageCount}} )
})
// 比较精简干练的写法
db.test.articles.find({'title':'wfc test'}).forEach( function(thisArticle){
thisArticle.image_count = NumberInt( thisArticle.article_images.length )
db.test.articles.save(thisArticle)
})
// 将文档的字段放入嵌套数组后，再删除该字段(数据结构修改)
db['test.game'].find({'article_image':{$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)
})
// 按名称分组统计
db['test.articles'].group({
key:{'name':1},
condition:{'name':{$exists:1}},
$reduce:function(curr, result) {
result.total += 1
},
initial:{total:0},
})
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