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From Wayne Conrad <wa...@databill.com>
Subject Re: Atomic update of multiple attachments?
Date Mon, 07 Feb 2011 23:59:05 GMT
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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