10.4.2. /db/doc/attachment — Apache CouchDB 2.0 Documentation

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# 10.4.2. `/db/doc/attachment`

`HEAD` `/{db}/{docid}/{attname}`

  Returns the HTTP headers containing a minimal amount of information about the specified attachment. The method supports the same query arguments as the `GET /{db}/{docid}/{attname}` method, but only the header information (including attachment size, encoding and the MD5 hash as an ETag), is returned.

  Parameters: | db – Database name docid – Document ID attname – Attachment name
  Request Headers:
  | If-Match – Document’s revision. Alternative to rev query parameter If-None-Match – Attachment’s base64 encoded MD5 binary digest. Optional
  Query Parameters:
  | rev (string) – Document’s revision. Optional
  Response Headers:
  | Accept-Ranges – Range request aware. Used for attachments with application/octet-stream content type Content-Encoding – Used compression codec. Available if attachment’s `content_type` is in `list of compressiable types` Content-Length – Attachment size. If compression codec was used, this value is about compressed size, not actual Content-MD5 – Base64 encoded MD5 binary digest ETag – Double quoted base64 encoded MD5 binary digest
  Status Codes: | 200 OK – Attachment exists 304 Not Modified – Attachment wasn’t modified if ETag equals specified If-None-Match header 401 Unauthorized – Read privilege required 404 Not Found – Specified database, document or attachment was not found

  Request:

      HEAD /recipes/SpaghettiWithMeatballs/recipe.txt HTTP/1.1
      Host: localhost:5984

  Response:

      HTTP/1.1 200 OK
      Accept-Ranges: none
      Cache-Control: must-revalidate
      Content-Encoding: gzip
      Content-Length: 100
      Content-MD5: vVa/YgiE1+Gh0WfoFJAcSg==
      Content-Type: text/plain
      Date: Thu, 15 Aug 2013 12:42:42 GMT
      ETag: "vVa/YgiE1+Gh0WfoFJAcSg=="
      Server: CouchDB (Erlang/OTP)

`GET` `/{db}/{docid}/{attname}`

  Returns the file attachment associated with the document. The raw data of the associated attachment is returned (just as if you were accessing a static file. The returned Content-Type will be the same as the content type set when the document attachment was submitted into the database.

  Parameters: | db – Database name docid – Document ID attname – Attachment name
  Request Headers:
  | If-Match – Document’s revision. Alternative to rev query parameter If-None-Match – Attachment’s base64 encoded MD5 binary digest. Optional
  Query Parameters:
  | rev (string) – Document’s revision. Optional
  Response Headers:
  | Accept-Ranges – Range request aware. Used for attachments with application/octet-stream Content-Encoding – Used compression codec. Available if attachment’s `content_type` is in `list of compressiable types` Content-Length – Attachment size. If compression codec is used, this value is about compressed size, not actual Content-MD5 – Base64 encoded MD5 binary digest ETag – Double quoted base64 encoded MD5 binary digest
  Response: | Stored content
  Status Codes: | 200 OK – Attachment exists 304 Not Modified – Attachment wasn’t modified if ETag equals specified If-None-Match header 401 Unauthorized – Read privilege required 404 Not Found – Specified database, document or attachment was not found

`PUT` `/{db}/{docid}/{attname}`

  Uploads the supplied content as an attachment to the specified document. The attachment name provided must be a URL encoded string. You must also supply either the `rev` query argument or the If-Match HTTP header for validation, and the HTTP headers (to set the attachment content type).

  If case when uploading an attachment using an existing attachment name, CouchDB will update the corresponding stored content of the database. Since you must supply the revision information to add an attachment to the document, this serves as validation to update the existing attachment.

  Note

  Uploading an attachment updates the corresponding document revision. Revisions are tracked for the parent document, not individual attachments.

  Parameters: | db – Database name docid – Document ID attname – Attachment name
  Request Headers:
  | Content-Type – Attachment MIME type. Required If-Match – Document revision. Alternative to rev query parameter
  Query Parameters:
  | rev (string) – Document revision. Required
  Response Headers:
  | Accept-Ranges – Range request aware. Used for attachments with application/octet-stream Content-Encoding – Used compression codec. Available if attachment’s `content_type` is in `list of compressiable types` Content-Length – Attachment size. If compression codec is used, this value is about compressed size, not actual Content-MD5 – Base64 encoded MD5 binary digest ETag – Double quoted base64 encoded MD5 binary digest
  Response JSON Object:
  | id (string) – Document ID ok (boolean) – Operation status rev (string) – Revision MVCC token
  Status Codes: | 200 OK – Attachment successfully removed 202 Accepted – Request was accepted, but changes are not yet stored on disk 400 Bad Request – Invalid request body or parameters 401 Unauthorized – Write privileges required 404 Not Found – Specified database, document or attachment was not found 409 Conflict – Document’s revision wasn’t specified or it’s not the latest

  Request:

      PUT /recipes/SpaghettiWithMeatballs/recipe.txt HTTP/1.1
      Accept: application/json
      Content-Length: 86
      Content-Type: text/plain
      Host: localhost:5984
      If-Match: 1-917fa2381192822767f010b95b45325b

      1. Cook spaghetti
      2. Cook meatballs
      3. Mix them
      4. Add tomato sauce
      5. ...
      6. PROFIT!

  Response:

      HTTP/1.1 201 Created
      Cache-Control: must-revalidate
      Content-Length: 85
      Content-Type: application/json
      Date: Thu, 15 Aug 2013 12:38:04 GMT
      ETag: "2-ce91aed0129be8f9b0f650a2edcfd0a4"
      Location: http://localhost:5984/recipes/SpaghettiWithMeatballs/recipe.txt
      Server: CouchDB (Erlang/OTP)

      {
          "id": "SpaghettiWithMeatballs",
          "ok": true,
          "rev": "2-ce91aed0129be8f9b0f650a2edcfd0a4"
      }

`DELETE` `/{db}/{docid}/{attname}`

  Deletes the attachment `attachment` of the specified `doc`. You must supply the `rev` query parameter or If-Match with the current revision to delete the attachment.

  Note

  Deleting an attachment updates the corresponding document revision. Revisions are tracked for the parent document, not individual attachments.

  Parameters: | db – Database name docid – Document ID
  Request Headers:
  | Accept – application/json text/plain If-Match – Document revision. Alternative to rev query parameter X-Couch-Full-Commit – Overrides server’s `commit policy`. Possible values are: `false` and `true`. Optional
  Query Parameters:
  | rev (string) – Document revision. Required batch (string) – Store changes in batch mode Possible values: `ok`. Optional
  Response Headers:
  | Content-Type – application/json text/plain; charset=utf-8 ETag – Double quoted document’s new revision
  Response JSON Object:
  | id (string) – Document ID ok (boolean) – Operation status rev (string) – Revision MVCC token
  Status Codes: | 200 OK – Attachment successfully removed 202 Accepted – Request was accepted, but changes are not yet stored on disk 400 Bad Request – Invalid request body or parameters 401 Unauthorized – Write privileges required 404 Not Found – Specified database, document or attachment was not found 409 Conflict – Document’s revision wasn’t specified or it’s not the latest

  Request:

      DELETE /recipes/SpaghettiWithMeatballs?rev=6-440b2dd39c20413045748b42c6aba6e2 HTTP/1.1
      Accept: application/json
      Host: localhost:5984

  Alternatively, instead of `rev` query parameter you may use If-Match header:

      DELETE /recipes/SpaghettiWithMeatballs HTTP/1.1
      Accept: application/json
      If-Match: 6-440b2dd39c20413045748b42c6aba6e2
      Host: localhost:5984

  Response:

      HTTP/1.1 200 OK
      Cache-Control: must-revalidate
      Content-Length: 85
      Content-Type: application/json
      Date: Wed, 14 Aug 2013 12:23:13 GMT
      ETag: "7-05185cf5fcdf4b6da360af939431d466"
      Server: CouchDB (Erlang/OTP)

      {
          "id": "SpaghettiWithMeatballs",
          "ok": true,
          "rev": "7-05185cf5fcdf4b6da360af939431d466"
      }

## HTTP Range Requests

HTTP allows you to specify byte ranges for requests. This allows the implementation of resumable downloads and skippable audio and video streams alike. This is available for all attachments inside CouchDB.

This is just a real quick run through how this looks under the hood. Usually, you will have larger binary files to serve from CouchDB, like MP3s and videos, but to make things a little more obvious, I use a text file here (Note that I use the application/octet-stream :header`Content-Type` instead of text/plain).

    shell> cat file.txt
    My hovercraft is full of eels!

Now let’s store this text file as an attachment in CouchDB. First, we create a database:

    shell> curl -X PUT http://127.0.0.1:5984/test
    {"ok":true}

Then we create a new document and the file attachment in one go:

    shell> curl -X PUT http://127.0.0.1:5984/test/doc/file.txt \
                -H "Content-Type: application/octet-stream" -d@file.txt
    {"ok":true,"id":"doc","rev":"1-287a28fa680ae0c7fb4729bf0c6e0cf2"}

Now we can request the whole file easily:

    shell> curl -X GET http://127.0.0.1:5984/test/doc/file.txt
    My hovercraft is full of eels!

But say we only want the first 13 bytes:

    shell> curl -X GET http://127.0.0.1:5984/test/doc/file.txt \
                -H "Range: bytes=0-12"
    My hovercraft

HTTP supports many ways to specify single and even multiple byte ranges. Read all about it in RFC 2616.

Note

Databases that have been created with CouchDB 1.0.2 or earlier will support range requests in 2.0, but they are using a less-optimal algorithm. If you plan to make heavy use of this feature, make sure to compact your database with CouchDB 2.0 to take advantage of a better algorithm to find byte ranges.

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