couchdb-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Daniele Testa <daniele.te...@gmail.com>
Subject Re: One view per "query"?
Date Fri, 10 Jun 2011 15:10:13 GMT
Hmm, if I have 10 million songs in my database, wouldn't that make
couchDB send all those 10 million documents to the client for the
sort?
That sounds crazy to me :)

Regards,
Daniele


2011/6/10 MK <mk@cognitivedissonance.ca>:
> On Fri, 10 Jun 2011 12:05:20 +0200
> Daniele Testa <daniele.testa@gmail.com> wrote:
>> That would mean that I need 3*4=12 views to accomodate all those
>> different "queries"?
>
> Only if you have to have your application 100% served directly
> from couch. However, IMO the view and shows make a lot more sense as
> ancillary functions for use by an external server.   Working that way,
> you could cover these twelve cases with a single view and a single
> function in the server proper, or 3 views and a single function, or 3
> views and 4 function functions in the server -- ie, you are free to
> choose how to do it.  For example, if you want to maintain the least
> amount of code, you'd go with the first option, a single view with a
> map defined:
>
> function (doc) {
>        emit (doc.title, [doc.artist, doc.genre, doc.insert_date]);
> }
>
> Dead simple, returns an array of all albums keyed by title.  Your
> server uses this like (js-esque pseudo code):
>
> function (criteria, value, sortby) {
>        var rawJSON = [whatever method you use to query couch];
>        // most languages have a means of turning JSON strings into
>           data structures:
>        var data = parse rawJSON;
>        var selected; // array type
>        for (e in data.rows) {
>        // you could also use a map type function here if you or your
> language have such
>                if (data.rows.criteria == value)
>                        selected.push(data.rows.criteria);
>        }
>        return Sort(selected, sortby);
> }
>
> How the "Sort" works depends on what lang you are programming in,
> sortby would probably be a comparison (eg: a.title > b.title ? b : a).
>
> If you want efficiency and you believe couch will do the most efficient
> job of selected data (which it probably will in most settings), then you
> might want the 3 views (these are all one liners, nb), and possibly
> even 3 views and 4 ordering methods in the server.
>
> From this perspective, views and shows make a lot of sense and are very
> useful -- they are like being able to incorporate simple, customized SQL
> queries into an sql db, providing you with a nice separation of
> concerns (you don't need any SQL in your server code, the db itself
> incorporates a "design" specific to the form of its content). But
> understood as the final points in a query, they just seem awkward, and
> you have no such separation.
>
>
> --
> "Enthusiasm is not the enemy of the intellect." (said of Irving Howe)
> "The angel of history[...]is turned toward the past." (Walter Benjamin)
>
>

Mime
View raw message