ElasticSearch CouchDB river - explicitly specify field type - couchdb

Question

I am using ElasticSearch river to index a CouchDB database of tweets.
The "created_at" field doesn't conform to the "date" type and gets indexed as a String.
How would I start a river with explicitly specifying that "created_at" is a Date, so that I could do range queries on it?
I tried the following river request, but it didn't work and the field was still indexed as a String:
curl -XPUT 'localhost:9200/_river/my_db/_meta' -d '{
"type" : "couchdb",
"couchdb" : {
"host" : "localhost",
"port" : 5984,
"db" : "testtweets",
"filter" : null
},
"index" : {
"index" : "my_testing",
"type" : "my_datetesting",
"properties" : {"created_at": {
"type" : "date",
"format" : "yyyy-MM-dd HH:mm:ss"
}
},
"bulk_size" : "100",
"bulk_timeout" : "10ms"
}
}'
My data looks like this:
{
"_id": "262856000481136640",
"_rev": "1-0ed7c0fe655974e236814184bef5ff16",
"contributors": null,
"truncated": false,
"text": "RT #edoswald: Ocean City MD first to show that #Sandy is no joke. Pier badly damaged, sea nearly topping the seawall http://t.co/D0Wwok4 ...",
"author_name": "Casey Strader",
"author_created_at": "2011-04-21 20:00:32",
"author_description": "",
"author_location": "",
"author_geo_enabled": false,
"source": "Twitter for iPhone",
"retweeted": false,
"coordinates": null,
"author_verified": false,
"entities": {
"user_mentions": [
{
"indices": [
3,
12
],
"id_str": "10433822",
"id": 10433822,
"name": "Ed Oswald",
"screen_name": "edoswald"
}
],
"hashtags": [
{
"indices": [
47,
53
],
"text": "Sandy"
}
],
"urls": [
{
"indices": [
117,
136
],
"url": "http://t.co/D0Wwok4",
"expanded_url": "http://t.co/D0Wwok4",
"display_url": "t.co/D0Wwok4"
}
]
},
"in_reply_to_screen_name": null,
"author_id_str": "285792303",
"retweet_count": 98,
"id_str": "262856000481136640",
"favorited": false,
"source_url": "http://twitter.com/download/iphone",
"author_screen_name": "Casey_Rae22",
"geo": null,
"in_reply_to_user_id_str": null,
"author_time_zone": "Eastern Time (US & Canada)",
"created_at": "2012-10-29 09:58:48",
"in_reply_to_status_id_str": null,
"place": null
}
Thanks!