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【已解决】MongoDB通过GridFS的API的put保存文件时添加额外信息

MongoDB crifan 184浏览 0评论

折腾:

【已解决】用Python去连接本地mongoDB去用GridFS保存文件

期间,已经可以用GridFS的API中的put去保存文件了。

现在需要去研究,如何在put时保存额外的信息。

去试试添加额外参数:

<code>audioFileId = fsCollection.put(
    audioFp,
    filename="Lots of Hearts_withContentType.mp3",
    content_type="application/mpeg",
    metadata={
        "keywords": {
                "series": "All Aboard Reading",
                "name": "Lots of Hearts",
                "keywords": [
                    "hearts"
                ],
                "leadingActor": "",
                "topic": "",
                "contentKeywords": []
        },
        "fitAgeStartYear": 3,
        "fitAgeEndYear": 6,
        "isFiction": False
    })
</code>

结果:

至少是正常运行的:

audioFileId=5abc9525a4bc715e187c6d6d

去看看结果:

<code>{
    "_id" : ObjectId("5abc9525a4bc715e187c6d6d"),
    "contentType" : "application/mpeg",
    "chunkSize" : 261120,
    "metadata" : {
        "keywords" : {
            "name" : "Lots of Hearts",
            "series" : "All Aboard Reading",
            "topic" : "",
            "contentKeywords" : [ ],
            "leadingActor" : "",
            "keywords" : [
                "hearts"
            ]
        },
        "isFiction" : false,
        "fitAgeStartYear" : 3,
        "fitAgeEndYear" : 6
    },
    "filename" : "Lots of Hearts_withContentType.mp3",
    "length" : 4795707,
    "uploadDate" : ISODate("2018-03-29T07:26:29.264Z"),
    "md5" : "955d19f230a5824e0fd5f41bee3dda21"
}
</code>

果然是可以的,可以把字典或者其他任何信息,直接放入metadata中去的。

然后看看如何读取metadata出来。

“get(file_id, session=None)

Get a file from GridFS by “_id”.

Returns an instance of GridOut, which provides a file-like interface for reading.

Parameters:

* file_id: “_id” of the file to get

* session (optional): a ClientSession

Changed in version 3.6: Added session parameter.”

此处get是返回的GridOut对象

http://api.mongodb.com/python/current/api/gridfs/grid_file.html#gridfs.grid_file.GridOut

class gridfs.grid_file.GridOut(root_collection, file_id=None, file_document=None, session=None)¶

而里面说了:

metadata¶

Metadata attached to this file.

This attribute is read-only.

所以应该可以直接读取出来的。

看到:

“Changed in version 3.0: Creating a GridOut does not immediately retrieve the file metadata from the server. Metadata is fetched when first needed.”

感觉是:

metadata是属于lazy load懒加载

如果没有用到,则不会去读取,第一次用到,才会去读取

但是我们写代码,理论上不需要关心。

去试试:

写代码期间,PyCharm也可以检测到GridOut了:

对应的,fs的collection的put也能看到了:

用代码:

<code>audioFileId = fsCollection.put(
    audioFp,
    filename="Lots of Hearts_withContentType.mp3",
    content_type="application/mpeg",
    metadata={
        "keywords": {
                "series": "All Aboard Reading",
                "name": "Lots of Hearts",
                "keywords": [
                    "hearts"
                ],
                "leadingActor": "",
                "topic": "",
                "contentKeywords": []
        },
        "fitAgeStartYear": 3,
        "fitAgeEndYear": 6,
        "isFiction": False
    })
logging.info("audioFileId=%s", audioFileId)

readOutAudioFile = fsCollection.get(audioFileId)
logging.info("readOutAudioFile=%s", readOutAudioFile)
audioFileMedata = readOutAudioFile.metadata
logging.info("audioFileMedata=%s", audioFileMedata)
</code>

调试期间,是可以看到metadata的:

可以获取metadata的:

<code>2018/03/29 03:33:52 LINE 83   INFO    audioFileId=5abc96dfa4bc715f473f0297
2018/03/29 03:36:03 LINE 86   INFO    readOutAudioFile=&lt;gridfs.grid_file.GridOut object at 0x110ec7c90&gt;
2018/03/29 03:36:38 LINE 88   INFO    audioFileMedata={u'keywords': {u'name': u'Lots of Hearts', u'series': u'All Aboard Reading', u'topic': u'', u'keywords': [u'hearts'], u'leadingActor': u'', u'contentKeywords': []}, u'isFiction': False, u'fitAgeStartYear': 3, u'fitAgeEndYear': 6}
</code>

【总结】

此处通过pymongo的gridfs的api中的put保存文件时,想要传递其他额外信息时,直接存在metadata中即可,比如

<code>with open(curAudioFullFilename) as audioFp :
    audioFileId = fsCollection.put(
        audioFp,
        filename="Lots of Hearts_withContentType.mp3",
        content_type=fileMimeType,
        metadata={
            "keywords": {
                    "series": "All Aboard Reading",
                    "name": "Lots of Hearts",
                    "keywords": [
                        "hearts"
                    ],
                    "leadingActor": "",
                    "topic": "",
                    "contentKeywords": []
            },
            "fitAgeStartYear": 3,
            "fitAgeEndYear": 6,
            "isFiction": False
        })
</code>

保存后的效果类似于:

<code>{
    "_id" : ObjectId("5abc997ea4bc71611bd37613"),
    "contentType" : "application/mpeg",
    "chunkSize" : 261120,
    "metadata" : {
        "keywords" : {
            "name" : "Lots of Hearts",
            "series" : "All Aboard Reading",
            "topic" : "",
            "contentKeywords" : [ ],
            "leadingActor" : "",
            "keywords" : [
                "hearts"
            ]
        },
        "isFiction" : false,
        "fitAgeStartYear" : 3,
        "fitAgeEndYear" : 6
    },
    "filename" : "Lots of Hearts_withContentType.mp3",
    "length" : 4795707,
    "uploadDate" : ISODate("2018-03-29T07:45:02.535Z"),
    "md5" : "955d19f230a5824e0fd5f41bee3dda21"
}
</code>

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