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From "Robert Newson (JIRA)" <>
Subject [jira] [Commented] (COUCHDB-1521) multipart parser gets multiple attachments mixed up
Date Wed, 08 Aug 2012 18:53:20 GMT


Robert Newson commented on COUCHDB-1521:

Upgrading this to blocker because a) it's very silly and b) I think worse things happen if
the two attachments were the same length.
> 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
>            Priority: Blocker
>             Fix For: 1.3
> 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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