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From Paul Davis <paul.joseph.da...@gmail.com>
Subject Re: Performance when sending array of keys to a view
Date Mon, 15 Mar 2010 19:33:06 GMT
When you post a keys array its doing a search through the view btree
to get each key. Where as with limit=20, it's searching once and then
scanning linearly.

What happens if you sort the array of keys before posting them?

On Mon, Mar 15, 2010 at 3:23 PM, Nick Poulden <nick@domine.co.uk> wrote:
> Hi,
>
> I'm developing a web app with node.js and CouchDB that displays nearby
> restaurants when given a lat/lng. At the moment I'm storing the restaurant
> data in CouchDB and a MySQL table with couchdb-key / lat / lng for each
> restaurant. I query MySQL for the nearby restaurants, then do a POST to a
> CouchDB view with the keys returned by MySQL.
>
> The problem is that there seems to be a huge difference in performance when
> sending the list of keys compared to a 'normal' view query.
>
> Here's an example:
>
> var db = CouchDB.db('restaurants');
> profiles.push(["Before Couch request: ", Number(new Date)])
> db.view('Restaurant/by_idx', {keys: restaurant_keys, include_docs: true,
> success: function(response) {
>  profiles.push(["After couch result: ", Number(new Date)])
> }});
>
> Start: 0 ms
> Before MySQL connect: 0 ms
> Got MySQL result: 17 ms
> Before Couch request: 18 ms
> After couch result: 272 ms
>
> If I replace line 3 with this:
>
> db.view('Restaurant/by_idx', {limit: 20, include_docs: true, success:
> function(response) {
>
> I get this:
>
> Start: 0ms
> Before MySQL connect: 0 ms
> Got MySQL result: 12 ms
> Before Couch request: 13 ms
> After couch result: 21 ms
>
> In both cases there are about 20 restaurants returned. The database has
> about 500 documents in it altogether. Can anyone shed some light on why
> there is such a big difference in response time?
>
> Thanks,
>
> Nick
>

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