Implementing Coherence aggregation queries using Java
Coherence is a distributed memory data grid product used to store and access large amounts of data. Implementing various aggregation queries for Coherence using Java can be accomplished through the following steps:
1. Add Coherence Maven dependency:
<dependency>
<groupId>com.oracle.coherence</groupId>
<artifactId>coherence</artifactId>
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</dependency>
2. Create a Coherence cluster configuration file, such as' Coherence cache config. xml ', to configure the cluster and data storage. In the configuration file, multiple caches and corresponding indexes can be defined.
<?xml version="1.0"?>
<coherence xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.oracle.com/coherence/coherence-operational-config
http://xmlns.oracle.com/coherence/coherence-operational-config/1.0/coherence-operational-config.xsd"
xmlns="http://xmlns.oracle.com/coherence/coherence-operational-config">
<cluster-config>
<member-identity>
<system-property>
<property-name>coherence.member</property-name>
<default-value>localhost</default-value>
</system-property>
</member-identity>
</cluster-config>
<caching-scheme-mapping>
<cache-mapping>
<cache-name>exampleCache</cache-name>
<scheme-name>exampleScheme</scheme-name>
</cache-mapping>
</caching-scheme-mapping>
<caching-schemes>
<distributed-scheme>
<scheme-name>exampleScheme</scheme-name>
<service-name>DistributedCache</service-name>
</distributed-scheme>
</caching-schemes>
</coherence>
3. Create Java classes, initialize the Coherence environment, and perform various aggregation query operations.
import com.tangosol.net.CacheFactory;
import com.tangosol.net.NamedCache;
import com.tangosol.util.InvocableMap;
import com.tangosol.util.QueryHelper;
import com.tangosol.util.filter.EqualsFilter;
public class CoherenceAggregateQueryExample {
public static void main(String[] args) {
//Initialize Coherence environment
CacheFactory.ensureCluster();
//Obtain or create a named cache
NamedCache cache = CacheFactory.getCache("exampleCache");
//Add sample data
cache.put("key1", 10);
cache.put("key2", 20);
cache.put("key3", 30);
//Execute Aggregate Query
InvocableMap.EntryAggregator<Integer, Integer, Integer> aggregator =
QueryHelper.createAggregator("sum");
Integer sum = (Integer) cache.aggregate(new EqualsFilter("getValue", null), aggregator);
//Output query results
System.out.println("Sum: " + sum);
//Close Coherence cluster
CacheFactory.shutdown();
}
}
The above example demonstrates how to use Coherence for aggregate queries. In the example, we initialized the Coherence environment, created a named cache, and added some sample data using the 'put' method. Then, we use the 'aggregate' method to perform an aggregate query, calculate the sum of all data, and print the results to the console.
Please note that this example only demonstrates a simple aggregation query operation. Different aggregation functions can be used in the 'createAggregator' method as needed to perform different aggregation calculation operations on different types of data.
In practical applications, you may need to adjust the Coherence cluster configuration file based on specific business needs and use more Coherence API methods to perform more complex data aggregation query operations. For more detailed information, you can refer to the official Oracle documentation or Coherence API documentation.
