Developing Arrow Flight SQL Client Applications for Dremio

Beginning with Dremio 21.0, you can use Apache Arrow Flight SQL to develop client applications that interact with Dremio. Apache Arrow Flight SQL is a new API developed by the Apache Arrow community for interacting with SQL databases. For more information about Apache Arrow Flight SQL, see the documentation for the Apache Arrow project.

Through Flight SQL, client applications can run queries, create prepared statements, and fetch metadata about the SQL dialect supported by datasource in Dremio, available types, defined tables, and more.

The requests for running queries are

• CommandExecute
• CommandStatementUpdate

The commands on prepared statements are:

• ActionClosePreparedStatementRequest: Closes a prepared statement.
• ActionCreatePreparedStatementRequest: Creates a prepared statement.
• CommandPreparedStatementQuery: Runs a prepared statement.
• CommandPreparedStatementUpdate: Runs a prepared statement that updates data.

The metadata requests that Dremio supports are:

• CommandGetDbSchemas: Lists the schemas that are in a catalog.
• CommandGetTables: Lists that tables that are in a catalog or schema.
• CommandGetTableTypes: Lists the table types that are supported in a catalog or schema. The types are Table, View, and System Table.
• CommandGetSqlInfo: Retrieves information about the datasource and the SQL dialect that it supports.

There are two clients already implemented and available in the Apache Arrow repository on GitHub for you to make use of:

• Client in C++
• Client in Java

Using the Sample Client

You can download and try out the sample client from https://github.com/dremio-hub/arrow-flight-sql-clients. Extract the content of the file and then, in a terminal window, change to the flight-sql-client-example directory.

Before running the sample client, ensure that you have met these prerequisites:

• Ensure that you have an instance of Dremio 21.0 or later configured and running.
• Ensure that you have a user account on that instance of Dremio.
• Add the Samples data lake to that instance of Dremio by clicking the plus (+) icon in the Data Lakes section of the Datasets page.
• Ensure that Java 8 or later (up to Java 15) is installed on the system on which you run the example commands.

Command Syntax for the Sample Client

Use this syntax when sending commands to the sample client:

Syntax for sending commands to sample client

Usage: java -jar flight-sql-sample-client-application.jar  -host localhost -port 32010 ...

 -command,--command <arg>                 Method to run
 -dsv,--disableServerVerification <arg>   Disable TLS server verification.
                                          Defaults to false.
 -host,--hostname <arg>                   Dremio co-ordinator hostname.
                                          Defaults to "localhost".
 -kstpass,--keyStorePassword <arg>        The jks keystore password.
 -kstpath,--keyStorePath <arg>            Path to the jks keystore.
 -pass,---password <arg>                  Dremio password.
 -pat,--personalAccessToken <arg>         Personal Access Token
 -port,--flightport <arg>                 Dremio flight server port.
                                          Defaults to 32010.
 -query,--query <arg>                     Query
 -schema,--schema <arg>                   Schema
 -sp,--sessionProperty <arg>              Key value pairs of
                                          SessionProperty, example: -sp
                                          schema='Samples."samples.dremio.
                                          com"' -sp key=value
 -table,--table <arg>                     Table
 -tls,--tls <arg>                         Enable encrypted connection.
                                          Defaults to false.
 -user,---username <arg>                  Dremio username.

Examples

The examples demonstrate what is returned for each of these requests:

• CommandGetDbSchemas
• CommandGetTables
• CommandGetTableTypes
• CommandExecute

Flight SQL Request: CommandGetDbSchemas

This command submits a CommandGetDbSchemas request to list the schemas in a catalog.

Example Request

Example GetDBSchemas request

java -jar flight-sql-sample-client-application.jar  -host <Dremio-coordinator-node> -port 32010 --username <Dremio-user-name> --password <Dremio-password> -command GetDbSchemas  

Example Output

GetDBSchemas output

catalog_name    db_schema_name
null            $scratch
null            @myUserName
null            INFORMATION_SCHEMA
null            Samples
null            sys

Flight SQL Request: CommandGetTables

This command submits a CommandGetTables request to list the tables that are in a catalog or schema.

Example Request

Example GetTables request

java -jar flight-sql-sample-client-application.jar  -host <Dremio-coordinator-node> -port 32010 --username <Dremio-user-name> --password <Dremio-password> -command GetTables -schema INFORMATION_SCHEMA

If you have a space in your schema, you can escape it like this:

Example GetTables request for spaces in schema names

java -jar flight-sql-sample-client-application.jar  -host <Dremio-coordinator-node> -port 32010 --username <Dremio-user-name> --password <Dremio-password> -command GetTables -schema "Samples\ (1).samples.dremio.com"

Example Output

GetTables output

catalog_name  db_schema_name            table_name  table_type
null          INFORMATION_SCHEMA    CATALOGS    SYSTEM_TABLE
null          INFORMATION_SCHEMA    COLUMNS         SYSTEM_TABLE
null          INFORMATION_SCHEMA    SCHEMATA    SYSTEM_TABLE
null          INFORMATION_SCHEMA    TABLES          SYSTEM_TABLE
null          INFORMATION_SCHEMA    VIEWS           SYSTEM_TABLE

Flight SQL Request: CommandGetTableTypes

This command submits a CommandTableTypes request to list the table types supported.

Example Request

Example GetTableTypes request

java -jar flight-sql-sample-client-application.jar  -host <Dremio-coordinator-node> -port 32010 --username <Dremio-user-name> --password <Dremio-password> -command GetTableTypes 

Example Output

GetTableTypes output

table_type
TABLE
SYSTEM_TABLE
VIEW

Flight SQL Request: CommandExecute

This command submits a CommandExecute request to run a single SQL statement.

Example Request

Example Execute request

java -jar flight-sql-sample-client-application.jar  -host <Dremio-coordinator-node> -port 32010 --username <Dremio-user-name> --password <Dremio-password> -command Execute -query 'SELECT * FROM Samples."samples.<Dremio-user-name>.com"."NYC-taxi-trips" limit 10'

Example Output

Execute output

pickup_datetime passenger_count trip_distance_mi fare_amount tip_amount total_amount
2013-05-27T19:15              1             1.26         7.5        0.0          8.0
2013-05-31T16:40              1             0.73         5.0        1.2          7.7
2013-05-27T19:03              2             9.23        27.5        5.0        38.33
2013-05-31T16:24              1             2.27        12.0        0.0         13.5
2013-05-27T19:17              1             0.71         5.0        0.0          5.5
2013-05-27T19:11              1             2.52        10.5       3.15        14.15
2013-05-31T16:41              5             1.01         6.0        1.1          8.6
2013-05-31T16:37              1             1.25         8.5        0.0         10.0
2013-05-31T16:39              1             2.04        10.0        1.5         13.0
2013-05-27T19:02              1            11.73        32.5       8.12        41.12

Code Samples

Creating a FlightSqlClient

Refer to this code sample to create a FlightClient. Then, wrap your FlightClient in a FlightSqlClient:

Create FlightSqlClient

// Wraps a FlightClient in a FlightSqlClient
FlightSqlClient flightSqlClient = new FlightSqlClient(flightClient);

// Be sure to close the FlightSqlClient after using it
flightSqlClient.close();

Retrieving a List of Database Schemas

This code issues a CommandGetSchemas metadata request:

Get database schemas

String catalog = null; // The catalog. (may be null)
String dbSchemaFilterPattern = null; // The schema filter pattern. (may be null)
FlightInfo flightInfo = flightSqlClient.getSchemas(catalog, dbSchemaFilterPattern);

Retrieving a List of Tables

This code issues a CommandGetTables metadata request:

Get tables

String catalog = null;  // The catalog. (may be null)
String dbSchemaFilterPattern = "Samples\\ (1).samples.dremio.com";  // The schema filter pattern. (may be null)
String tableFilterPattern = null;  // The table filter pattern. (may be null)
List<String> tableTypes = null;  // The table types to include. (may be null)
boolean includeSchema = false;  // True to include the schema upon return, false to not include the schema.
FlightInfo flightInfo = flightSqlClient.getTables(catalog, dbSchemaFilterPattern, tableFilterPattern, tableTypes, includeSchema);

Retrieving a List of Table Types That a Database Supports

This code issues a CommandGetTableTypes metadata request:

Get table types that database supports

FlightInfo flightInfo = flightSqlClient.getTableTypes();

Running a Query

This code issues a CommandExecute request:

CommandExecute request code

FlightInfo flightInfo = flightSqlClient.execute("SELECT * FROM Samples.\"samples.myUserName.com\".\"NYC-taxi-trips\" limit 10");

Consuming Data Returned for a Query

Consume returned data

FlightInfo flightInfo; // Use a FlightSqlClient method to get a FlightInfo

// 1. Fetch each partition sequentially (though this can be done in parallel)
for (FlightEndpoint endpoint : flightInfo.getEndpoints()) {

  // 2. Get a stream of results as Arrow vectors
  try (FlightStream stream = flightSqlClient.getStream(endpoint.getTicket())) {

    // 3. Iterate through the stream until the end
    while (stream.next()) {

      // 4. Get a chunk of results (VectorSchemaRoot) and print it to the console
      VectorSchemaRoot vectorSchemaRoot = stream.getRoot();
      System.out.println(vectorSchemaRoot.contentToTSVString());
    }
  }
}