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From Paul Davis <>
Subject Re: [jira] [Commented] (COUCHDB-1521) multipart parser gets multiple attachments mixed up
Date Thu, 09 Oct 2014 21:30:43 GMT
It sends them out, I'm not sure if we read them coming in though.

On Thu, Oct 9, 2014 at 3:30 PM, Robert Newson (JIRA) <> wrote:
>     [
> Robert Newson commented on COUCHDB-1521:
> ----------------------------------------
> Jan enhanced multipart so that each part can have headers (including filenames), which
I think was the fix for mixups?
>> multipart parser gets multiple attachments mixed up
>> ---------------------------------------------------
>>                 Key: COUCHDB-1521
>>                 URL:
>>             Project: CouchDB
>>          Issue Type: Bug
>>          Components: HTTP Interface
>>    Affects Versions: 1.2
>>            Reporter: Jens Alfke
>>            Assignee: Randall Leeds
>> When receiving a document PUT in multipart format, CouchDB gets the attachments and
MIME parts mixed up. Instead of looking at the headers of a MIME part to identify which attachment
it is (most likely by using the 'filename' property of the 'Content-Disposition:' header),
it processes the attachments according to the order in which their metadata objects appear
in the JSON body's '_attachments:' object.
>> The problem with this is that JSON objects (dictionaries) are _not_ ordered collections.
I know that Erlang's implementation of them (as linked lists of key/value pairs) happens to
be ordered, and I think some JavaScript implementations have the side effect of preserving
order; but in many languages these are implemented as hash tables and genuinely unordered.
>> This means that when a program written in such a language converts a native object
to JSON, it has no control over (and probably no knowledge of) the order in which the keys
of the JSON object are written out. This makes it impossible to then write the attachments
in the same order.
>> The only workaround seems to be for the program to implement its own custom JSON
encoder just so that it can write object keys in a known order (probably sorted), which then
enables it to write the attachment bodies in the same order.
>> NOTE: This is the flip side of COUCHDB-1368 which I filed last year; that bug has
to do with the same ordering issue when CouchDB _generates_ multipart responses (and presents
similar problems for clients not written in Erlang.)
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