Using Java to Implement Couchbase Aggregated Queries
Couchbase is a high-performance open source distributed NoSQL database that provides rich functionality and flexible data models. The following are the steps to implement various aggregation queries in Couchbase using Java.
1. Add Couchbase Java SDK dependencies (Maven coordinates):
<dependencies>
<dependency>
<groupId>com.couchbase.client</groupId>
<artifactId>java-client</artifactId>
<version>VERSION</version>
</dependency>
</dependencies>
Please replace 'VERSION' with the appropriate Couchbase SDK version.
2. Create a Couchbase cluster connection:
Cluster cluster = Cluster.connect("couchbase://localhost", "username", "password");
Bucket bucket = cluster.bucket("bucketname");
Collection collection = bucket.defaultCollection();
Please replace 'localhost' with the host name or IP address of the Couchbase server, 'username' and 'password' with the credentials for logging into the Couchbase cluster, and 'bucketname' with the name of the bucket to query.
3. Execute aggregation query:
Below are several common aggregation queries and their Java code examples.
-Count the number of documents:
JsonObject result = collection.aggregate(JsonArray.from(
JsonObject.create().put("$count", "*")
)).rowsAsObject().get(0);
long count = result.getLong("$1");
System. out. println ("Number of documents:"+count);
-Sum:
JsonObject result = collection.aggregate(JsonArray.from(
JsonObject.create().put("$group", JsonObject.create()
.put("_id", "")
.put("total", JsonObject.create()
.put("$sum", "$amount")
)
)
)).rowsAsObject().get(0);
double sum = result.getDouble("total");
System. out. println ("total:"+sum);
-Average:
JsonObject result = collection.aggregate(JsonArray.from(
JsonObject.create().put("$group", JsonObject.create()
.put("_id", "")
.put("average", JsonObject.create()
.put("$avg", "$amount")
)
)
)).rowsAsObject().get(0);
double average = result.getDouble("average");
System. out. println ("average:"+average);
-Find maximum and minimum values:
JsonObject result = collection.aggregate(JsonArray.from(
JsonObject.create().put("$group", JsonObject.create()
.put("_id", "")
.put("maxAmount", JsonObject.create()
.put("$max", "$amount")
)
.put("minAmount", JsonObject.create()
.put("$min", "$amount")
)
)
)).rowsAsObject().get(0);
double maxAmount = result.getDouble("maxAmount");
double minAmount = result.getDouble("minAmount");
System. out. println ("maximum value:"+maxAmount);
System. out. println ("minimum value:"+minAmount);
These examples demonstrate how to implement aggregate queries for Couchbase using Java. You can make corresponding modifications and adjustments according to your own needs and data model.
Finally, when you no longer need to connect to the Couchbase cluster, remember to close the connection and release resources:
collection.close();
bucket.close();
cluster.disconnect();
