Database Reference
In-Depth Information
Listing 3.3
Get all of the Tweets in a collection
> db.tweets.find()
{
"_id"
: ObjectId(
"51e6d70cd13954bd0dd9e09d"
), ... }
{
"_id"
: ObjectId(
"51e6d70cd13954bd0dd9e09e"
), ... }
...
has more
Source: Chapter3/find_all_tweets.js
Listing 3.4
Get all of the Tweets from a single hour
> var NOVEMBER = 10;
//Months are zero-indexed.
> var query = {
...
"timestamp"
:{
...
"$gte"
: +new Date(2011, NOVEMBER, 15, 10),
...
"$lt"
: +new Date(2011, NOVEMBER, 16, 11)
...
}
... };
> db.tweets.find(query).count();
22169
Source: Chapter3/tweets_from_one_hour.js
Listing 3.5
Sort Tweets by time published
> db.tweets.find().sort({
"timestamp"
: -1})
{
"_id"
: ObjectId(
"51e6d713d13954bd0ddaa097"
), ... }
{
"_id"
: ObjectId(
"51e6d713d13954bd0ddaa096"
), ... }
has more
Source: Chapter3/most_recent_tweets.js
3.10
Sorting Documents: Finding the Most Recent Tweets
To find the most recent Tweets, we will have to sort the data. MongoDB provides a
sort
function that will order the Tweet by a specified field. Listing
3.5
shows an
example of how to use
sort
to order data by timestamp. Because we used “
”in
the value of the key value pair, MongoDB will return the data in descending order.
For ascending order, use “1”.
Without the index created in Sect.
3.7
, we would have caused the error shown in
Listing
3.6
. Even with a relatively small collection, MongoDB cannot sort the data
in a manageable amount of time, however with an index it is very fast.
1
