druid/docs/querying/sql-jdbc.md

id	title	sidebar_label
sql-jdbc	SQL JDBC driver API	JDBC driver API

Apache Druid supports two query languages: Druid SQL and native queries. This document describes the SQL language.

You can make Druid SQL queries using the Avatica JDBC driver. We recommend using Avatica JDBC driver version 1.17.0 or later. Note that as of the time of this writing, Avatica 1.17.0, the latest version, does not support passing connection string parameters from the URL to Druid, so you must pass them using a Properties object. Once you've downloaded the Avatica client jar, add it to your classpath and use the connect string jdbc:avatica:remote:url=http://BROKER:8082/druid/v2/sql/avatica/.

When using the JDBC connector for the examples or in general, it's helpful to understand the parts of the connect string stored in the url variable:

• jdbc:avatica:remote:url= is prepended to the hostname and port.
• The hostname and port number for your Druid deployment depends on whether you want to connect to the Router or a specific Broker. For more information, see Connection stickiness. In the case of the quickstart deployment, the hostname and port are http://localhost:8888, which connects to the Router running on your local machine.
• The SQL endpoint in Druid for the Avatica driver is /druid/v2/sql/avatica/.

Example code:

// Connect to /druid/v2/sql/avatica/ on your Broker.
String url = "jdbc:avatica:remote:url=http://localhost:8082/druid/v2/sql/avatica/";

// Set any connection context parameters you need here
// Or leave empty for default behavior.
Properties connectionProperties = new Properties();

try (Connection connection = DriverManager.getConnection(url, connectionProperties)) {
  try (
      final Statement statement = connection.createStatement();
      final ResultSet resultSet = statement.executeQuery(query)
  ) {
    while (resultSet.next()) {
      // process result set
    }
  }
}

For a runnable example that includes a query that you might run, see Examples.

It is also possible to use a protocol buffers JDBC connection with Druid, this offer reduced bloat and potential performance improvements for larger result sets. To use it apply the following connection url instead, everything else remains the same

String url = "jdbc:avatica:remote:url=http://localhost:8082/druid/v2/sql/avatica-protobuf/;serialization=protobuf";

The protobuf endpoint is also known to work with the official Golang Avatica driver

Table metadata is available over JDBC using connection.getMetaData() or by querying the "INFORMATION_SCHEMA" tables. For an example of this, see Get the metadata for a datasource.

Connection stickiness

Druid's JDBC server does not share connection state between Brokers. This means that if you're using JDBC and have multiple Druid Brokers, you should either connect to a specific Broker or use a load balancer with sticky sessions enabled. The Druid Router process provides connection stickiness when balancing JDBC requests, and can be used to achieve the necessary stickiness even with a normal non-sticky load balancer. Please see the Router documentation for more details.

Note that the non-JDBC JSON over HTTP API is stateless and does not require stickiness.

Dynamic parameters

You can use parameterized queries in JDBC code, as in this example:

PreparedStatement statement = connection.prepareStatement("SELECT COUNT(*) AS cnt FROM druid.foo WHERE dim1 = ? OR dim1 = ?");
statement.setString(1, "abc");
statement.setString(2, "def");
final ResultSet resultSet = statement.executeQuery();

Examples

The following section contains two complete samples that use the JDBC connector:

• Get the metadata for a datasource shows you how to query the INFORMATION_SCHEMA to get metadata like column names.
• Query data runs a select query against the datasource.

You can try out these examples after verifying that you meet the prerequisites.

For more information about the connection options, see Client Reference.

Prerequisites

Make sure you meet the following requirements before trying these examples:

• A supported Java version, such as Java 8

• Avatica JDBC driver. You can add the JAR to your CLASSPATH directly or manage it externally, such as through Maven and a pom.xml file.

• An available Druid instance. You can use the micro-quickstart configuration described in Quickstart (local). The examples assume that you are using the quickstart, so no authentication or authorization is expected unless explicitly mentioned.

• The example wikipedia datasource from the quickstart is loaded on your Druid instance. If you have a different datasource loaded, you can still try these examples. You'll have to update the table name and column names to match your datasource.

Get the metadata for a datasource

Metadata, such as column names, is available either through the INFORMATION_SCHEMA table or through connect.getMetaData(). The following example uses the INFORMATION_SCHEMA table to retrieve and print the list of column names for the wikipedia datasource that you loaded during a previous tutorial.

import java.sql.*;
import java.util.Properties;

public class JdbcListColumns {

    public static void main(String args[]) throws SQLException
    {
        // Connect to /druid/v2/sql/avatica/ on your Router. 
        // You can connect to a Broker but must configure connection stickiness if you do. 
        String url = "jdbc:avatica:remote:url=http://localhost:8888/druid/v2/sql/avatica/";

        String query = "SELECT COLUMN_NAME,* FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'wikipedia' and TABLE_SCHEMA='druid'";
        // Set any connection context parameters you need here
        // Or leave empty for default behavior.
        Properties connectionProperties = new Properties();

        try (Connection connection = DriverManager.getConnection(url, connectionProperties)) {
            try (
                    final Statement statement = connection.createStatement();
                    final ResultSet rs = statement.executeQuery(query)
            ) {
                while (rs.next()) {
                    String columnName = rs.getString("COLUMN_NAME");
                    System.out.println(columnName);
                }
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }

    }
}

Query data

Now that you know what columns are available, you can start querying the data. The following example queries the datasource named wikipedia for the timestamps and comments from Japan. It also sets the query context parameter sqlTimeZone . Optionally, you can also parameterize queries by using dynamic parameters.

import java.sql.*;
import java.util.Properties;

public class JdbcCountryAndTime {

    public static void main(String args[]) throws SQLException
    {
        // Connect to /druid/v2/sql/avatica/ on your Router. 
        // You can connect to a Broker but must configure connection stickiness if you do. 
        String url = "jdbc:avatica:remote:url=http://localhost:8888/druid/v2/sql/avatica/";

        //The query you want to run.
        String query = "SELECT __time, isRobot, countryName, comment FROM wikipedia WHERE countryName='Japan'";
        // Set any connection context parameters you need here
        // Or leave empty for default behavior.
        Properties connectionProperties = new Properties();
        connectionProperties.setProperty("sqlTimeZone", "America/Los_Angeles");

        try (Connection connection = DriverManager.getConnection(url, connectionProperties)) {
            try (
                    final Statement statement = connection.createStatement();
                    final ResultSet rs = statement.executeQuery(query)
            ) {
                while (rs.next()) {
                    Timestamp timeStamp = rs.getTimestamp("__time");
                    String comment = rs.getString("comment");
                    System.out.println(timeStamp);
                    System.out.println(comment);
                }
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }

    }
}