GridFS存储文件

MongoDB针对于文件，尤其是大文件，专门设计了一套接口，叫做：GridFS

此处总结一下GridFS的使用心得。

TODO：

• 如何基于Flask搭建一个文件下载服务，甚至可以支持断点续传功能。把之前相关代码贴过来。
• 把更多帖子内容整理至此
  • GridFS
    • 【已解决】GridFS保存文件时如何得到文件的id或_id
    • 【已解决】用Python去连接本地mongoDB去用GridFS保存文件
    • 【已解决】MongoDB的GridFS中基于文件名或id去下载文件
    • 【已解决】MongoDB的GridFS中只返回file的chunks的个数而不返回chunks.data
    • 【基本解决】Python中把wma、wav等格式音频转换为mp3
    • 【未解决】Mongo中更新gridfs中的mp3文件的metadata信息且尽量保持id不变
    • 【已解决】远程的mongoDB中GridFS报错：AttributeError GridFS object has no attribute totalSize
    • 【规避解决】Flask-PyMongo中如何查询gridfs中的文件
    • 【已解决】如何用PyMongo中的GridFS的put去保存添加文件
    • 【已解决】PyMongo中GridFS的exists始终检测不到文件已存在
    • 【已解决】Flask中Mongo的GridFS数据如何保存为绝对路径的下载文件地址
    • 【已解决】MongoDB通过GridFS的API的put保存文件时添加额外信息
    • 【已解决】PyMongo的GridFS中使用fs的collection去put出错：TypeError Collection object is not callable
    • 【已解决】把本地mp3文件存入在线Mongo中且填写meta信息
    • 【已解决】Flask中连接远程MongoDB数据库的gridfs并返回查询到的文件数据
  • 和其中mongofiles相关的：
    • 【已解决】用mongofiles去删除GridFS中的文件
    • 【无法也无须解决】用mongofiles给GridFS中添加文件时添加额外参数属性字段
    • 【已解决】mongofiles中put保存和get下载获取时指定文件名

一些供参考的资料：

• GirdFS官网文档
  • GridFS — MongoDB Manual 3.6
• Pymongo
  • GridFS的例子
    • GridFS Example — PyMongo 3.6.1 documentation
  • GridFS的API
    • gridfs – Tools for working with GridFS — PyMongo 3.6.1 documentation
  • 相关的grid_file
    • grid_file – Tools for representing files stored in GridFS — PyMongo 3.6.1 documentation

一些GirdFS的心得

通过id查找gridfs中file文件

注意不是：

> db.fs.files.find({"id": "5b556ee47f4d38ba6a189222"})
> db.fs.files.find({"_id": "5b556ee47f4d38ba6a189222"})

而是ObjectId("5b556ee47f4d38ba6a189222")：

> db.fs.files.find({"_id": ObjectId("5b556ee47f4d38ba6a189222")})
{ "_id" : ObjectId("5b556ee47f4d38ba6a189222"), "contentType" : "audio/mpeg", "chunkSize" : 261120, "metadata" : { "song" : { "singers" : [ "ChuChu TV" ] }, "series" : { "number" : 0, "name" : "" }, "topics" : [ ], "storybook" : { "publisher" : "", "isFiction" : "未知", "lexileIndex" : "", "awards" : "", "authors" : [ ], "foreignCountry" : "" }, "keywords" : { "fromName" : [ "Finger", "Family" ], "other" : [ ], "fromContent" : [ "Daddy Finger" ] }, "name" : "Finger Family", "resourceType" : "song", "mainActors" : [ ], "contentAbstract" : "", "isSeries" : false, "fitAgeStart" : 3, "fitAgeEnd" : 6, "fileInfo" : { "isAudio" : true, "contentType" : "audio/mpeg", "name" : "Finger Family.mp3", "suffix" : "mp3" } }, "filename" : "Finger Family.mp3", "length" : 2604280, "uploadDate" : ISODate("2018-07-23T06:00:04.925Z"), "md5" : "946564effc4c0a835c55564377e7d819" }
>

删除文件

举例：

> db.fs.files.deleteOne({"_id": ObjectId("5b556ee47f4d38ba6a189222")})
{ "acknowledged" : true, "deletedCount" : 1 }

格式化带缩进美观的输出结果

后面加上：.pretty()

> db.fs.files.find({"_id": ObjectId("5b556ee47f4d38ba6a189222")}).pretty()
{
    "_id" : ObjectId("5b556ee47f4d38ba6a189222"),
    "contentType" : "audio/mpeg",
    "chunkSize" : 261120,
    "metadata" : {
        "song" : {
            "singers" : [
                "ChuChu TV"
            ]
        },
        "series" : {
            "number" : 0,
            "name" : ""
        },
        "topics" : [ ],
        "storybook" : {
            "publisher" : "",
            "isFiction" : "未知",
            "lexileIndex" : "",
            "awards" : "",
            "authors" : [ ],
            "foreignCountry" : ""
        },
        "keywords" : {
            "fromName" : [
                "Finger",
                "Family"
            ],
            "other" : [ ],
            "fromContent" : [
                "Daddy Finger"
            ]
        },
        "name" : "Finger Family",
        "resourceType" : "song",
        "mainActors" : [ ],
        "contentAbstract" : "",
        "isSeries" : false,
        "fitAgeStart" : 3,
        "fitAgeEnd" : 6,
        "fileInfo" : {
            "isAudio" : true,
            "contentType" : "audio/mpeg",
            "name" : "Finger Family.mp3",
            "suffix" : "mp3"
        }
    },
    "filename" : "Finger Family.mp3",
    "length" : 2604280,
    "uploadDate" : ISODate("2018-07-23T06:00:04.925Z"),
    "md5" : "946564effc4c0a835c55564377e7d819"
}
>