Thanks for all the good ideas - Couchdb definitely has an active
community willing to help. I'm going to try to run some tests over
the holidays, with this and the array intersection methods on the
server side, and see if it's worth pursuing further.
Dan Woolley
profile: http://www.linkedin.com/in/danwoolley
company: http://woolleyrobertson.com
product: http://dwellicious.com
blog: http://tzetzefly.com
On Dec 15, 2008, at 6:25 PM, Paul Davis wrote:
I thought of a possible way to possible overcome this that may or may
not work depending on the underlying data.
General scheme is to basically make a view for each filter that you
want to be able to combine. Then with a group reduce you could figure
out the number of records in each range. Then fetch the records for
the view with the fewest results and then multi get against all other
filters removing keys if they come back with an error.
More concretely:
Each view would be:
map:
function(doc) {emit(doc.filter_field, 1);}
reduce:
function(keys, values) {return sum(values);}
To get the count for a specific range you'd do:
GET
http://127.0.0.1:5984/db_name/_view/filters/by_field_x?group=true&startkey=min&endkey=max
And in the client code you would merge each of the results. For things
with a more continuous range like price, you may need to bucket
appropriately. This query should be run once for each field.
Then say we want to filter on fields X, Y, Z (assuming num_in(X) <
num_in(Y) < num_in(Z))
DocIds = GET
http://127.0.0.1:5984/db_name/_view/filters/by_field_X?startkey=minX&endkey=maxX
Then intersect with a call to Y and Z views:
POST
http://127.0.0.1:5984/db_name/_view/filters/by_field_Y?startkey=minY&endkey=maxY
BODY: {"keys": [DocIds]}
That make sense?
Paul
On Sun, Dec 14, 2008 at 12:06 PM, Dan Woolley <[email protected]>
wrote:
I'm researching Couchdb for a project dealing with real estate
listing data.
I'm very interested in Couchdb because the schema less nature,
RESTful
interface, and potential off-line usage with syncing fit my problem
very
well. I've been able to do some prototyping and search on ranges
for a
single field very successfully. I'm having trouble wrapping my
mind around
views for a popular use case in real estate, which is a query like:
Price = 350000-400000
Beds = 4-5
Baths = 2-3
Any single range above is trivial, but what is the best model for
handling
this AND scenario with views? The only thing I've been able to
come up with
is three views returning doc id's - which should be very fast -
with an
array intersection calculation on the client side. Although I
haven't tried
it yet, that client side calculation worries me with a potential
document
with 1M records - the client would potentially be dealing with
calculating
the intersection of multiple 100K element arrays. Is that a
realistic
calculation?
Please tell me there is a better model for dealing with this type of
scenario - or that this use case is not well suited for Couchdb at
this time
and I should move along.
Dan Woolley
profile: http://www.linkedin.com/in/danwoolley
company: http://woolleyrobertson.com
product: http://dwellicious.com
blog: http://tzetzefly.com
