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From Karl Seguin <>
Subject Re: noobie questions
Date Mon, 24 Oct 2011 08:29:57 GMT
Thanks a lot for all the answers. I got everything I wanted :)


On Mon, Oct 24, 2011 at 4:00 PM, CGS <> wrote:

> Hi Karl,
> First of all, welcome!
> I am no expert, but few things I can clarify for you from what I understood
> from the documentation posted at:
> I.**editions/1/en/index.html<>
> II. (the short version of the first)
> 1. Views are completed at the first time the request is triggered and
> updated only when the DB is updated. So, for example, if you want a view to
> be updated at certain number of documents, you just need to make a bulk
> operation on the DB. You can find more at**
> editions/1/en/views.html<>(efficient
> 2. Depending on what language (programming, scripting etc.) you use, there
> are different application which can help you. I used only one, CouchBEAM,
> which is based on Erlang and it provides the API you ask for: retrieve a
> document, retrieve the value of a key from the document, modify only that
> value (or key) as you like it and save the document (don't forget to remove
> _rev from the modified document before saving it - I usually kept forgetting
> that) without you caring about what's behind. I don't think this is the only
> application of this type, so, just check the CouchDB list of application
> based on this product and choose which one is the most suitable for you.
> 3. Check page 2 (bulk operation) from II for _delete. You need two
> operations only: retrieve the _rev's for the documents you want to delete
> and a bulk operation to delete them. It is even simpler if you create a view
> to give you back all those _rev's and make a script to connect with the bulk
> operation. Another option is to keep those posts, but not to show them.
> 4. CouchDB is designed for web. Therefore, you can pass the keys values as
> queries in the address bar. Check the documentation I mentioned at point 1
> and you will have there some query examples like
> |/blog/_design/docs/_view/by_**date?key="2009/01/30 18:04:11"|.
> I hope this will help you for the start. From my experience, I can say
> there are two things you have to keep them in mind when you operate with
> CouchDB:
> A. The documents are not necessarily within the same format (containing the
> same set of keys). That is usually forgotten by the SQL developers and here
> some may find CouchDB more difficult.
> B. CouchDB has JavaScript to interface with the web. If there is something
> missing in CouchDB as functionality, there can be added by the means of
> JavaScript.
> Sometimes is not easy to work with CouchDB and there are things which can
> be done in SQL faster or easier, but once you get a bit of grip on CouchDB,
> you will see it's not so hard. I repeat, I am not an expert in CouchDB and I
> haven't used all its functions yet because I wasn't in need of using them
> all. But as much as I used CouchDB, JavaScript and Erlang were powerful
> enough to create what I needed.
> Cheers,
> On 10/24/2011 08:28 AM, Karl Seguin wrote:
>> Hi,
>> I'm just starting to learn CouchDB and I've accumulated four questions.
>> First, I only found some vague references, but are views only updated on
>> read request? (assuming there's something to update). There's no built-in
>> mechanism to have views updated in the background say for every X
>> changed/new documents or X seconds?
>> Secondly, it seems like if you want to update a document, you need to send
>> the complete document over. I understand that, given CouchDB's versioning,
>> this makes sense. In theory, would it be possible for CouchDB to expose an
>> API to allow updates to specific fields, then on the backend, it would
>> clone
>> the document and overwrite the field.  Again, I know that isn't possible
>> with the current API, I'm just wondering if there's anything that would
>> stop
>> that from working. You'd essentially send over the doc_id, rev, the field
>> name and the new value.
>> Third, any bulk update or delete needs to be done in code by loop through
>> the result of a view? Say, I want to delete all the posts older than 1
>> year.
>> I create  view keyed by the post date, I query the view with my specific
>> filter, and then I loop through it deleting each document? It's pretty
>> much
>> the same story for updates, but I can use the bulk update api. There's no
>> direct analog to delete from posts where date<  ?, it's more of a select
>> id
>> from posts where date<  ? then delete those ids. Right?
>> Forth, and I'm sorry for asking this, I realize it's asked a lot, but I
>> couldnt' figure it out despite that...I'm trying to retrieve all of the
>> posts with a specific tag, sorted by date. My view looks like:
>> function(doc) {
>>   if (doc.doc_type != 'post') { return; }
>>   for(var tag in doc.tags) {
>>     emit([doc.dated, doc.tags[tag]], null);
>>   }
>> }
>> I was hoping that a query like this might work:
>> for row in db.view('application/post_by_**tags', key='[{}, "blah"]'):
>>   print row
>> But it doesn't.
>> Thanks for the help,
>> Karl

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