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From "Paul Davis" <paul.joseph.da...@gmail.com>
Subject Re: General Q about CouchDB
Date Wed, 17 Dec 2008 18:47:47 GMT
James,

Near as I know, it's not possible to do an arbitrary tree depth first
tree sort only using a parent link. Someone may yet come up with a
clever trick to do it, but for the moment no one has thought of a
solution.

You mention storing the entire path but also seem to discard the idea.
Any reason. If you're in a threaded thinger like you got, then you
would have access to the path of the node to which your replying. And
the topology would be stable so no worries about moving paths etc.
Having the full path should allow you to do what you want fairly
easily. I think.

Paul Davis

On Wed, Dec 17, 2008 at 1:30 PM, James Marca
<jmarca@translab.its.uci.edu> wrote:
> On Wed, Dec 17, 2008 at 01:49:20AM +0100, Jan Lehnardt wrote:
>>
>> On 16 Dec 2008, at 20:54, Christopher McComas wrote:
>>
>> >Chris,
>> >Thanks. One question, concern I might have with that would be just
>> >spelling something differently, but that shouldn't be too big of an
>> >issue.
>> >
>> >To my next question, what would be the best way to structure
>> >comments for a blog post, where they have their own author,
>> >timestamp, and entry?  Again, this is fairly straight-forward with
>> >a relational db using a foreign key.
>>
>> Same concept ;)
>>
>> See http://www.cmlenz.net/archives/2007/10/couchdb-joins for details.
>>
>
> Apologies for forking a topic slightly, but this maps onto a problem I
> am having.  And apologies if this has been answered.  I'm new here, I
> *did* look, but I haven't a solution I like yet.
>
> The article's suggested solution will allow comments nested one-layer
> deep.  Am I missing something, or is it nearly impossible to collect
> comments on comments in one go?  My thought would be to replace "post"
> with "parent", but then the view map can't build the sort order
> properly, no?
>
> For example:
>
> {
>  "_id": "ABCDEF",
>  "_rev": "123456",
>  "type": "comment",
>  "post": "myslug",
>  "author": "jack",
>  "content": "…"}
> }, {
>  "_id": "DEFABC",
>  "_rev": "123456",
>  "type": "comment",
>  "post": "myslug",
>  "parent": "myslug",
>  "author": "jane",
>  "content": "…"
> }, {
>  "_id": "FABC1234",
>  "_rev": "123456",
>  "type": "comment",
>  "post": "myslug",
>  "parent": "DEFABC",
>  "author": "john",
>  "content": "…"
> }
>
> Winging it with untested code, the best guess I can make for nested
> sorting is something like:
>
> function(doc) {
>  if (doc.type == "post") {
>    emit([doc._id, 0], doc);
>  } else if (doc.type == "comment") {
>    if(doc.parent == null || doc.parent=doc.post){
>         // could have a date here for the second sort key?
>         emit([doc.post, doc._id, 1], doc);
>    }else{
>         // this fails for arbitrarily deep nesting.
>         emit([doc.post,doc.parent,doc._id],doc);
>    }
>  }
> }
>
> As I understand it, the problem is that without storing the complete
> hierarchy of comments, you can't reproduce the correct nested sorting
> in one go.  To quote the "how to store hierarchical data" page in the
> wiki, "Store the full path to each node as an attribute in that node's
> document."
>
> On the other hand, a perfectly valid solution that uses client-side
> javascript to build the doc (this is a blog after all) would be to
> just use dom functions to append to parents, something like
>
> jQuery.each(commentArray, function(){
>        jQuery("#"+this.parent)
>         .append("<div id='"+this._id+"'class='comment'>"
>                 +this.content
>                 +"</div>");
> });
>
> While this makes it possible to nest comments on the page of
> most browswers that support jQuery etc., my real question is about the
> inner workings of couchdb, whether it is possible to make the sort
> with some clever view definition trickery.
>
> Note that I have absolutely zero clue about reduce functions and their
> uses.  Maybe you can use reduce to generate arbitrarily deep nesting
> of comments with just a "parent" field??
>
> James
>
>> Cheers
>> Jan
>> --
>>
>>
>> >
>> >
>> >Thanks,
>> >
>> >On Tue, Dec 16, 2008 at 2:51 PM, Chris Anderson <jchris@gmail.com>
>> >wrote:
>> >
>> >>On Tue, Dec 16, 2008 at 11:46 AM, Christopher McComas
>> >><mccomas.chris@gmail.com> wrote:
>> >>>Would it be wrong to try to do the category piece as related in
>> >>>CouchDB?
>> >>>What would be the best way to do it, so that you can have a page,
>> >>>myblog.com/categories/this-category/ that'd then display all the
>> >>>entries
>> >>for
>> >>>that category? What would be proper?
>> >>
>> >>Having a category field on the blog post itself is a fine way to do
>> >>this.
>> >>
>> >>Eg:
>> >>
>> >>{
>> >>"title":"Blah",
>> >>"author":"Chris",
>> >>"category":"music",
>> >>"date": ...
>> >>}
>> >>
>> >>Writing a view that sorts posts by category and date would be simple
>> >>with this sort of data structure. Of course if you wanted to rename a
>> >>category later you'd need to touch all the documents that listed it,
>> >>so this solution is more like tagging than categories, but should
>> >>fulfill the need.
>> >>
>> >>
>> >>--
>> >>Chris Anderson
>> >>http://jchris.mfdz.com
>> >>
>
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