FireDAC Components for HDFS

Build 21.0.7930

Writing Data Access Code

This section provides a simple scenario that shows how to write the basic data access code needed to pipe HDFS data into your application. The code example chains FireDAC components like TFDConnection and TFDQuery and executes a SELECT query with simple GUI components.

Setting Connection Properties

To begin accessing HDFS through a TFDConnection component and then other FireDAC components, create a connection and link the FireDAC components:

  1. Initialize the HDFS component: Add a TFDPhysHDFSDriverLink object to your project.
  2. Link with a TFDConnection object: Set the DriverName property of the TFDConnection object to the Driver Id of the component, CDataHDFS.
  3. Define connection properties through the TFDPhysHDFSConnectionDefParams object. This object enables you to use Code Insight and compiler syntax checking.

FDConnection1.Name := 'SQLTest';
FDConnection1.DriverName := 'CDataHDFS';
with FDConnection1.Params as TFDPhysCDataHDFSConnectionDefParams do begin
    ...
end;

You can also set connection properties through the FDManager function. See Connection Definitions for other ways to define connections.

Execute SQL Queries to HDFS

You can use the TFDQuery object to execute any SQL statement.

  1. Set the Connection property of a TFDQuery object to a TFDConnection instance.

  2. Set the Connected property of the TFDConnection object to True to open the connection.
  3. Call the Open method to execute SELECT queries with a TFDQuery object.

FDQuery1.Connection := FDConnection1;
FDConnection1.Connected := true;
FDQuery1.Active := true;
FDQuery1.Open('SELECT * FROM Files WHERE FileId = ''119116''');

See Querying Data for more information on selecting HDFS data with the TFDQuery class.

Copyright (c) 2021 CData Software, Inc. - All rights reserved.
Build 21.0.7930