Java
Pinot provides a native java client to execute queries on the cluster. The client makes it easier for user to query data. The client is also tenant-aware and thus is able to redirect the queries to the correct broker.
Installation
You can use the client by including the following dependency -
<dependency>
<groupId>org.apache.pinot</groupId>
<artifactId>pinot-java-client</artifactId>
<version>0.5.0</version>
</dependency>
You can also build the code for java client locally and use it.
Usage
Here's an example of how to use the pinot-java-client
to query Pinot.
import org.apache.pinot.client.Connection;
import org.apache.pinot.client.ConnectionFactory;
import org.apache.pinot.client.Request;
import org.apache.pinot.client.ResultSetGroup;
import org.apache.pinot.client.ResultSet;
/**
* Demonstrates the use of the pinot-client to query Pinot from Java
*/
public class PinotClientExample {
public static void main(String[] args) {
// pinot connection
String zkUrl = "localhost:2181";
String pinotClusterName = "PinotCluster";
Connection pinotConnection = ConnectionFactory.fromZookeeper(zkUrl + "/" + pinotClusterName);
String query = "SELECT COUNT(*) FROM myTable GROUP BY foo";
// set queryType=sql for querying the sql endpoint
Request pinotClientRequest = new Request("sql", query);
ResultSetGroup pinotResultSetGroup = pinotConnection.execute(pinotClientRequest);
ResultSet resultTableResultSet = pinotResultSetGroup.getResultSet(0);
int numRows = resultTableResultSet.getRowCount();
int numColumns = resultTableResultSet.getColumnCount();
String columnValue = resultTableResultSet.getString(0, 1);
String columnName = resultTableResultSet.getColumnName(1);
System.out.println("ColumnName: " + columnName + ", ColumnValue: " + columnValue);
}
}
Connection Factory
The client provides a ConnectionFactory
class to create connections to a Pinot cluster. The factory supports the following methods to create a connection -
Zookeeper (Recommended) - Comma seperated list of zookeeper of the cluster. This is the recommended method which can redirect queries to appropriate brokers based on tenant/table.
Broker list - Comma seperated list of the brokers in the cluster. This should only be used in standalone setups or for POC, unless you have a load balancer setup for brokers.
Properties file - You can also put the broker list as
brokerList
in a properties file and provide the path to that file to the factory. This should only be used in standalone setups or for POC, unless you have a load balancer setup for brokers.
Here's an example demonstrating all methods of Connection factory -
Connection connection = ConnectionFactory.fromZookeeper
("some-zookeeper-server:2191/zookeeperPath");
Connection connection = ConnectionFactory.fromProperties("demo.properties");
Connection connection = ConnectionFactory.fromHostList
("broker-1:1234", "broker-2:1234", ...);
Query Methods
You can run the query in both blocking as well as async manner. Use
Connection.execute(org.apache.pinot.client.Request)
for blocking queriesConnection.executeAsync(org.apache.pinot.client.Request)
for asynchronous queries that return a future object.
ResultSetGroup resultSetGroup =
connection.execute(new Request("sql", "select * from foo..."));
// OR
Future<ResultSetGroup> futureResultSetGroup =
connection.executeAsync(new Request("sql", "select * from foo..."));
You can also use PreparedStatement
to escape query parameters. We don't store the Prepared Statement in the database and hence it won't increase the subsequent query performance.
PreparedStatement statement =
connection.prepareStatement(new Request("sql", "select * from foo where a = ?"));
statement.setString(1, "bar");
ResultSetGroup resultSetGroup = statement.execute();
// OR
Future<ResultSetGroup> futureResultSetGroup = statement.executeAsync();
Result Set
Results can be obtained with the various get methods in the first ResultSet, obtained through the getResultSet(int)
method:
Request request = new Request("sql", "select foo, bar from baz where quux = 'quuux'");
ResultSetGroup resultSetGroup = connection.execute(request);
ResultSet resultTableResultSet = pinotResultSetGroup.getResultSet(0);
for (int i = 0; i < resultSet.getRowCount(); ++i) {
System.out.println("foo: " + resultSet.getString(i, 0));
System.out.println("bar: " + resultSet.getInt(i, 1));
}
PQL Queries
If queryFormat pql
is used in the Request
, there are some differences in how the results can be accessed, depending on the query.
In the case of aggregation, each aggregation function is within its own ResultSet. A query with multiple aggregation function will return one result set per aggregation function, as they are computed in parallel.
ResultSetGroup resultSetGroup =
connection.execute(new Request("pql", "select max(foo), min(foo) from bar"));
System.out.println("Number of result groups:" +
resultSetGroup.getResultSetCount(); // 2, min(foo) and max(foo)
ResultSet resultSetMax = resultSetGroup.getResultSet(0);
System.out.println("Max foo: " + resultSetMax.getInt(0));
ResultSet resultSetMin = resultSetGroup.getResultSet(1);
System.out.println("Min foo: " + resultSetMin.getInt(0));
In case of aggregation with GROUP BY
, there will be as many ResultSets as the number of aggregations, each of which will contain multiple results grouped by a grouping key.
ResultSetGroup resultSetGroup =
connection.execute(
new Request("pql", "select min(foo), max(foo) from bar group by baz"));
System.out.println("Number of result groups:" +
resultSetGroup.getResultSetCount(); // 2, min(foo) and max(foo)
ResultSet minResultSet = resultSetGroup.getResultSet(0);
for(int i = 0; i < minResultSet.length(); ++i) {
System.out.println("Minimum foo for " + minResultSet.getGroupKeyString(i, 1) +
": " + minResultSet.getInt(i));
}
ResultSet maxResultSet = resultSetGroup.getResultSet(1);
for(int i = 0; i < maxResultSet.length(); ++i) {
System.out.println("Maximum foo for " + maxResultSet.getGroupKeyString(i, 1) +
": " + maxResultSet.getInt(i));
}
This section is only applicable for PQL endpoint, which is deprecated and will be deleted soon. For more information about the endpoints, visit Querying Pinot.
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