Apache Ignite Aggregation Query

Apache Ignite is an in memory computing platform that provides rich aggregation query capabilities. The following are some common aggregation query types supported by Apache Ignite and corresponding example implementations. 1. COUNT: Calculate the number of records For example, if there is a table named Person that contains fields id, name, and age, the following SQL query can be used to calculate the number of records in the table: SELECT COUNT(*) FROM Person 2. SUM: Sum For example, on the Person table mentioned above, the following SQL query can be used to calculate the sum of age fields: SELECT SUM(age) FROM Person 3. AVG: Find the average value For example, on the Person table mentioned above, the following SQL query can be used to calculate the average value of the age field: SELECT AVG(age) FROM Person 4. MIN: Find the minimum value For example, on the Person table mentioned above, the following SQL query can be used to find the minimum value of the age field: SELECT MIN(age) FROM Person 5. MAX: Find the maximum value For example, on the Person table mentioned above, the following SQL query can be used to find the maximum value of the age field: SELECT MAX(age) FROM Person 6. GROUP BY: Group calculation For example, on the Person table mentioned above, the following SQL query can be used to group by name field and calculate the number of records in each group: SELECT name, COUNT(*) FROM Person GROUP BY name 7. HAVING: Group filtering For example, on the Person table mentioned above, the following SQL query can be used to find groups with age greater than or equal to 30 and calculate the number of records in each group: SELECT name, COUNT(*) FROM Person GROUP BY name HAVING age >= 30 It should be noted that in order to use Apache Ignite for aggregation queries, data needs to be stored in Ignite first, and Ignite Cache can be used to store data. The definition of table structure and sample data is as follows: //Define the Person class public class Person implements Serializable { @QuerySqlField(index = true) private String id; @QuerySqlField private String name; @QuerySqlField private int age; //Getter and setter methods } //Create Ignite cache IgniteCache<String, Person> cache = ignite.getOrCreateCache("personCache"); //Write data to cache cache.put("1", new Person("1", "Alice", 25)); cache.put("2", new Person("2", "Bob", 30)); cache.put("3", new Person("3", "Alice", 35)); Through the above definitions and data examples, SQL queries can be used for various aggregation operations. The specific query statements and code calls can be adjusted according to the above examples.