Menu
I have those items in my MongoDB collection:
{x: 1, y: 60, z:100}
{x: 1, y: 60, z:100}
{x: 1, y: 60, z:100}
{x: 2, y: 60, z:100}
{x: 2, y: 60, z:100}
{x: 3, y: 60, z:100}
{x: 4, y: 60, z:100}
{x: 4, y: 60, z:100}
{x: 5, y: 60, z:100}
{x: 6, y: 60, z:100}
{x: 6, y: 60, z:100}
{x: 6, y: 60, z:100}
{x: 7, y: 60, z:100}
{x: 7, y: 60, z:100}
I want to query the distinct values of x (i.e. [1, 2, 3, 4, 5, 6, 7]) ... but I only want a part of them (similar to what we can obtain with skip(a) and limit(b)).
How do I do that with the java driver of MongoDB (or with spring-data-mongodb if possible) ?
326
The limit() function in MongoDB is used to specify the maximum number of results to be returned. Only one parameter is required for this function.to return the number of the desired result. Sometimes it is required to return a certain number of results after a certain number of documents. The skip() can do this job.
To count the unique values, use "distinct()" rather than "find()", and "length" rather than "count()". The first argument for "distinct" is the field for which to aggregate distinct values, the second is the conditional statement that specifies which rows to select.
in mongo shell is simple with aggregate framework:
db.collection.aggregate([{$group:{_id:'$x'}}, {$skip:3}, {$limit:5}])
for java look: use aggregation framework in java
183
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
