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Date: Mon, 17 Aug 2009 14:11:51 -0700
Message-ID: <b8602b350908171411j29b5c378u9ba5e5544ebedb00@mail.gmail.com>
Subject: Re: How to code an advanced search
From: Adam Jacob <adam@opscode.com>
To: user@couchdb.apache.org
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On Sun, Aug 16, 2009 at 1:29 AM, Fr=E9d=E9ric Malo<fredericmalo@gmail.com> =
wrote:
> For example, imagine a music database as iTunes. I would like to create a
> script to query such as :
>
> Sort all songs by genre then album =A0:
> - with 3 or 5 stars
> - artist name matching "floyd"
> - duration between 5 and 8 minutes
> - heard last week (perhaps another couch database, logging user actions)
> - ....
>
> All the parameters are optional. Users can choose to filter with only 2 o=
r 5
> parameters. Other parameters should be added.

The simple answer is "you can't get there from here", at least not
like you are thinking.  You have a couple of options:

* Refactor each of those questions into a single view for each, with
the key pointing to a list of songs that match.
* As the user adds more options, you are actually adding an extra
request for each view
* Use the built in sorting to get the sort order
* Query all the various required views and return the final result set

This is following a similar pattern to the ones used by Full text
search engines - you are using CouchDB to create the indexes for you,
which return light-weight data that gets culled based on your
requirements.

Another option would be to actually put all this data into a full text
engine, and use that. (Solr is a nice option here, and perhaps
couchdb-lucene.)

Don't be afraid to do a little more work on the systems that talk to
CouchDB - often when you find yourself reaching for a Join, instead
reach for multiple queries and doing the computation of the final
match set yourself.

Adam

(I've seen a system that does just this, only with CDB indexes rather
than CouchDB, do very complex queries and filtering against every
hotel in America at very, very high speed.)

--=20
Opscode, Inc.
Adam Jacob, CTO
T: (206) 508-4759 E: adam@opscode.com