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From Robert Johnson <rob...@rowanshire.net>
Subject Re: Atomic update of multiple attachments?
Date Tue, 08 Feb 2011 00:07:49 GMT
Wayne

I think we can achieve what you need. Its midnight in the UK so I will think on it & get
back to you tomorrow.

Bob

Wayne Conrad <wayne@databill.com> wrote:

>Bob, One of my needs is that requestors can get the most recent 
>"complete" set of attachments, even while a new set is being assembled. 
>  I've no sense of what it takes to work with previous version of a 
>document, esp. since (as I understand it) replication doesn't transfer 
>old revisions of documents.  Do you think your idea can be made to work 
>with this need?
>
>I'm wondering if something can be done that's similar to how we 
>create/rename files in Unix.  Can I create a temporary document, load it 
>up with attachments, and then rename it?
>
>Wayne
>
>On 02/07/11 16:38, Robert Johnson wrote:
>>
>> Create your document with attributes "eventual_attachment _count" (set this to the
expected count) and "attachment_count_so_far" (set this to zero).
>> As you add each attachment, increment "attachment_count_so_far"
>>
>> Create a view which only emits when "attachment_count_so_far" = "eventual_attachment
_count"
>>
>>
>> For update:-
>>
>> Remove docs and decrement "attachment_count_so_far"
>> Reset "eventual_attachment _count"if necessary
>> Add new attachments and increment "attachment_count_so_far"
>>
>> Does this work for you?
>>
>> Bob
>>
>> On 7 Feb 2011, at 23:25, Wayne Conrad wrote:
>>
>>> Is there anything I can do to achieve the illusion of atomic update of a set
of attachments?  Here's the effect I'd like:
>>>
>>> For create:
>>> 1. Create a document.
>>> 2. Add attachments to it.
>>> 3. Only now does the document and all of its attachments become visible.
>>>
>>> For update:
>>> 1. Delete all of the document's attachments.
>>> 2. Add a new set of attachments to the document.
>>> 3. Only now does the new set of attachments appear to replace the old.
>>>
>>> I'm using Couchdb 1.0.2 and CouchRest 1.0.1.  I'm not opposed to cheating to
achieve my goal.  Suggestions of "Did you think of doing this-other-thing instead?" are also
welcome.
>>
>
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