Access Avro Data as a Remote Oracle Database



Use the Oracle ODBC Gateway and Heterogeneous Services technology to access Avro data from your Oracle system.

The Oracle Database Gateway for ODBC and Heterogeneous Services technology enable you to connect to ODBC data sources as remote Oracle databases. This article shows how to use the CData ODBC Driver for Avro to create a database link from Avro to Oracle and to query Avro data through the SQL*Plus tool. You can also create the database link and execute queries from SQL Developer.

Connect to Avro as an ODBC Data Source

Information for connecting to Avro follows, along with different instructions for configuring a DSN in Windows and Linux environments.

Connect to your local Avro file(s) by setting the URI connection property to the location of the Avro file.

Windows

If you have not already, first specify connection properties in an ODBC DSN (data source name). This is the last step of the driver installation. You can use the Microsoft ODBC Data Source Administrator to create and configure ODBC DSNs.

Note: If you need to modify the DSN or create other Avro DSNs, you must use a system DSN and the bitness of the DSN must match your Oracle system. You can access and create 32-bit DSNs on a 64-bit system by opening the 32-bit ODBC Data Source Administrator from C:\Windows\SysWOW64\odbcad32.exe.

Linux

If you are installing the CData ODBC Driver for Avro in a Linux environment, the driver installation predefines a system DSN. You can modify the DSN by editing the system data sources file (/etc/odbc.ini) and defining the required connection properties.

/etc/odbc.ini

[CData Avro Source] Driver = CData ODBC Driver for Avro Description = My Description URI = C:/folder/table.avro

For specific information on using these configuration files, please refer to the help documentation (installed and found online).

Set Connection Properties for Compatibility with Oracle

The driver provides several connection properties that streamline accessing Avro data just as you would an Oracle database. Set the following properties when working with Avro data in SQL*Plus and SQL Developer. For compatibility with Oracle, you will need to set the following connection properties, in addition to authentication and other required connection properties.

  • MapToWVarchar=False

    Set this property to map string data types to SQL_VARCHAR instead of SQL_WVARCHAR. By default, the driver uses SQL_WVARCHAR to accommodate various international character sets. You can use this property to avoid the ORA-28528 Heterogeneous Services data type conversion error when the Unicode type is returned.

  • MaximumColumnSize=4000

    Set this property to restrict the maximum column size to 4000 characters.

  • IncludeDualTable=True

    Set this property to mock the Oracle DUAL table. SQL Developer uses this table to test the connection.

Linux Configuration

In Linux environments, Oracle uses UTF-8 to communicate with the unixODBC Driver manager, whereas the default driver encoding is UTF-16. To resolve this, open the file /opt/cdata/cdata-driver-for-avro/lib/cdata.odbc.avro.ini in a text editor and set the encoding.

cdata.odbc.avro.ini

[Driver] DriverManagerEncoding = UTF-8

Configure the ODBC Gateway, Oracle Net, and Oracle Database

Follow the procedure below to set up an ODBC gateway to Avro data that enables you to query live Avro data as an Oracle database.

  1. Create the file initmyavrodb.ora in the folder oracle-home-directory/hs/admin and add the following setting:

    initmyavrodb.ora

    HS_FDS_CONNECT_INFO = "CData Avro Sys"
  2. Add an entry to the listener.ora file. This file is located in oracle-home-directory/NETWORK/admin.

    If you are using the Database Gateway for ODBC, your listener.ora needs to have a SID_LIST_LISTENER entry that resembles the following:

    listener.ora

    SID_LIST_LISTENER = (SID_LIST = (SID_DESC = (SID_NAME = myavrodb) (ORACLE_HOME = your-oracle-home) (PROGRAM = dg4odbc) ) )

    If you are using Heterogeneous Services, your listener.ora needs to have a SID_LIST_LISTENER entry that resembles the following:

    listener.ora

    SID_LIST_LISTENER = (SID_LIST = (SID_DESC = (SID_NAME = myavrodb) (ORACLE_HOME = your-oracle-home) (PROGRAM = hsodbc) ) )
  3. Add the connect descriptor below in tnsnames.ora, located in oracle-home-directory/NETWORK/admin:

    tnsnames.ora

    myavrodb = (DESCRIPTION= (ADDRESS=(PROTOCOL=tcp)(HOST=localhost)(PORT=1521)) (CONNECT_DATA=(SID=myavrodb)) (HS=OK) )
  4. Restart the listener.
  5. Test the configuration with the following command:

    tnsping myavrodb
  6. Open SQL*Plus and create the database link with the command below:

    CREATE DATABASE LINK myavrodb CONNECT TO "user" IDENTIFIED BY "password" USING 'myavrodb';

You can now execute queries in SQL*Plus like the one below (note the double quotation marks around the table name):

SELECT * from "SampleTable_1"@myavrodb WHERE Column2 = 'value_2';

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The Avro ODBC Driver is a powerful tool that allows you to connect with live data from Avro, directly from any applications that support ODBC connectivity.

Access Avro data like you would a database - read, write, and update through a standard ODBC Driver interface.