用于删除字段中部分文本的 MongoDB 更新语句 [英] MongoDB update statement to remove a portion of text in a field

问题描述

我有一个名为Url"的字段的 mongoDB 集合.这个集合中有很多记录.在此字段中，它始终包含以下文本:

I have a mongoDB collection with a field called "Url". There are many records in this collection. Inside this field, it always contains this text below:

"http://image-assets.s3.us-west-2.amazonaws.com/"例如 "http://image-assets.s3.us-west-2.amazonaws.com/folder1/folder2/blah.jpg"

我想删除http://image-assets.s3.us-west-2.amazonaws.com/"，因此最终结果应该类似于folder1/folder2/blah.jpg"

I would like to remove the portion of "http://image-assets.s3.us-west-2.amazonaws.com/", so the final result should look like "folder1/folder2/blah.jpg"

想写一个mongodb的更新语句，不知道从何下手.我可以想到两件事:(a) 删除前 x 个字符，或 (b) 用空值替换文本.但是文本包含很多斜杠 (/)

I would like to write a mongodb update statement, I don't know where to start. I can think of two things: (a) remove the first x number of characters, or (b) replace the text with a null. However the text includes a lot of slashes (/)

感谢您的帮助.

推荐答案

这个带有更新结果的聚合查询将起作用:

This aggregation query with update on the result will work:

db.urls.aggregate( [ 
  { 
      $project: { 
          url: { 
              $split: [ 
                  "$url", 
                  "http://image-assets.s3.us-west-2.amazonaws.com/"
              ] 
          }
      }
  } 
] ).forEach( doc => db.urls.updateOne( { _id: doc._id }, { $set: { url: doc.url[1] } } )

有了这两个输入文件:

{ url: "http://image-assets.s3.us-west-2.amazonaws.com/folder1/folder2/blah.jpg" }
{ url: "http://image-assets.s3.us-west-2.amazonaws.com/folder1/folder2/blah2.jpg" }

更新后的 url 字段会有值:

The updated url field will have values:

folder1/folder2/blah.jpg
folder1/folder2/blah2.jpg

<小时>

使用要更新的 URL 字符串添加对 url 字段的检查.在上述聚合查询中的 $project 阶段之前添加这个 $match 阶段.

Adding a check for url field with the URL string to be updated. Add this $match stage before the $project stage in the above aggregation query.

请注意，在正则表达式搜索字符串中^ 表示以"开头，而.(点)以\ 为前缀(反斜杠)，因此它仅被视为一个点(而不是正则表达式元字符).

Note that in the regex search string ^ means "starts with", and the . (dot) is prefixed with a \ (backslash) so that it is considered as a dot only (not as regex meta-character).

  { 
      $match: { 
          url: { $regex: '^http://image-assets\.s3\.us-west-2\.amazonaws\.com/' } 
      } 
  }, 

这篇关于用于删除字段中部分文本的 MongoDB 更新语句的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！