Implementing Apache Ignite aggregate queries using Java
Apache Ignite is an in memory computing platform that allows for distributed computing and data storage. The following are methods for implementing various aggregation queries in Apache Ignite using Java:
1. Create an Apache Ignite cluster configuration file, ignite.xml, specifying information such as the cluster name and nodes. For example:
<ignite xmlns="http://ignite.apache.org/schema/diagnostics">
<bean class="org.apache.ignite.configuration.IgniteConfiguration">
<property name="igniteInstanceName" value="MyIgniteCluster"/>
<property name="peerClassLoadingEnabled" value="true"/>
<-- Configure other properties -->
</bean>
</ignite>
2. Load the cluster configuration file in Java code and start the Ignite cluster. You can use ignore core and ignore spring dependencies.
import org.apache.ignite.Ignition;
public class IgniteCluster {
public static void main(String[] args) {
Ignition. setClientMode (true)// If the corresponding ignite node is not started, client mode will automatically start
Ignition. start ("ignite. xml")// Load the configuration file and start the cluster
//Other operations of the Ignite cluster
}
}
3. Create a cache and load data. In Ignite, data is stored in a cache in memory. You can configure the name of the cache, the type of key value pairs, and so on by creating a CacheConfiguration object.
import org.apache.ignite.Ignition;
import org.apache.ignite.configuration.CacheConfiguration;
import org.apache.ignite.Ignite;
import org.apache.ignite.IgniteCache;
public class IgniteCluster {
public static void main(String[] args) {
Ignition.setClientMode(true);
Ignite ignite = Ignition.start("ignite.xml");
//Create cache configuration
CacheConfiguration<Integer, String> cacheCfg = new CacheConfiguration<>("myCache");
cacheCfg.setIndexedTypes(Integer.class, String.class);
//Create cache
IgniteCache<Integer, String> cache = ignite.getOrCreateCache(cacheCfg);
//Load data into cache
cache.put(1, "value1");
cache.put(2, "value2");
//Other operations of the Ignite cluster
}
}
4. Conduct aggregation queries. Ignite's SQL query syntax allows for various aggregation queries, such as calculating averages, totals, and so on. You can use ignore core and ignore spring dependencies.
import org.apache.ignite.Ignition;
import org.apache.ignite.Ignite;
import org.apache.ignite.IgniteCache;
import org.apache.ignite.IgniteException;
import org.apache.ignite.cache.query.SqlFieldsQuery;
import java.util.List;
public class IgniteCluster {
public static void main(String[] args) throws IgniteException {
Ignition.setClientMode(true);
Ignite ignite = Ignition.start("ignite.xml");
CacheConfiguration<Integer, String> cacheCfg = new CacheConfiguration<>("myCache");
cacheCfg.setIndexedTypes(Integer.class, String.class);
IgniteCache<Integer, String> cache = ignite.getOrCreateCache(cacheCfg);
cache.put(1, "value1");
cache.put(2, "value2");
//Execute Aggregate Query
SqlFieldsQuery avgQuery = new SqlFieldsQuery("SELECT AVG(_val) FROM String").setSchema("PUBLIC");
List<List<?>> avgResult = cache.query(avgQuery).getAll();
SqlFieldsQuery sumQuery = new SqlFieldsQuery("SELECT SUM(_val) FROM String").setSchema("PUBLIC");
List<List<?>> sumResult = cache.query(sumQuery).getAll();
//Process query results
if (!avgResult.isEmpty()) {
Double avg = (Double) avgResult.get(0).get(0);
System. out. println ("average:"+avg);
}
if (!sumResult.isEmpty()) {
Double sum = (Double) sumResult.get(0).get(0);
System. out. println ("total:"+sum);
}
ignite.close();
}
}
The above example code demonstrates how to implement a simple Ignite cluster using Java, create a cache, and perform aggregate queries for average and total values. Note that this is only a small part of Ignite's features, and more features and usage can be found in the official documentation.
