Build a PostgreSQL Interface for AlloyDB Data using the CData JDBC Driver

There are a vast number of PostgreSQL clients available on the Internet. From standard Drivers to BI and Analytics tools, PostgreSQL is a popular interface for data access. Using our JDBC Drivers, you can now create PostgreSQL entry-points that you can connect to from any standard client.

To access AlloyDB data as a PostgreSQL database, use the CData JDBC Driver for AlloyDB and a JDBC foreign data wrapper (FDW). In this article, we compile the FDW, install it, and query AlloyDB data from PostgreSQL Server.

Connect to AlloyDB Data as a JDBC Data Source

To connect to AlloyDB as a JDBC data source, you will need the following:

• Driver JAR path: The JAR is located in the lib subfolder of the installation directory.

• Driver class:

  cdata.jdbc.alloydb.AlloyDBDriver
  

• JDBC URL: The URL must start with "jdbc:alloydb:" and can include any of the connection properties in name-value pairs separated with semicolons.

  The following connection properties are usually required in order to connect to AlloyDB.

  • Server: The host name or IP of the server hosting the AlloyDB database.
  • User: The user which will be used to authenticate with the AlloyDB server.
  • Password: The password which will be used to authenticate with the AlloyDB server.

  You can also optionally set the following:

  • Database: The database to connect to when connecting to the AlloyDB Server. If this is not set, the user's default database will be used.
  • Port: The port of the server hosting the AlloyDB database. This property is set to 5432 by default.

  Authenticating with Standard Authentication

  Standard authentication (using the user/password combination supplied earlier) is the default form of authentication.

  No further action is required to leverage Standard Authentication to connect.

  Authenticating with pg_hba.conf Auth Schemes

  There are additional methods of authentication available which must be enabled in the pg_hba.conf file on the AlloyDB server.

  Find instructions about authentication setup on the AlloyDB Server here.

  Authenticating with MD5 Authentication

  This authentication method must be enabled by setting the auth-method in the pg_hba.conf file to md5.

  Authenticating with SASL Authentication

  This authentication method must be enabled by setting the auth-method in the pg_hba.conf file to scram-sha-256.

  Authenticating with Kerberos

  The authentication with Kerberos is initiated by AlloyDB Server when the ∏ is trying to connect to it. You should set up Kerberos on the AlloyDB Server to activate this authentication method. Once you have Kerberos authentication set up on the AlloyDB Server, see the Kerberos section of the help documentation for details on how to authenticate with Kerberos.

  Built-in Connection String Designer

  For assistance in constructing the JDBC URL, use the connection string designer built into the AlloyDB JDBC Driver. Either double-click the JAR file or execute the jar file from the command-line.

  java -jar cdata.jdbc.alloydb.jar
  

  Fill in the connection properties and copy the connection string to the clipboard.

  👁 Using the built-in connection string designer to generate a JDBC URL (Salesforce is shown.)
  

  A typical JDBC URL is below:

  jdbc:alloydb:User=alloydb;Password=admin;Database=alloydb;Server=127.0.0.1;Port=5432
  

Build the JDBC Foreign Data Wrapper

The Foreign Data Wrapper can be installed as an extension to PostgreSQL, without recompiling PostgreSQL. The jdbc2_fdw extension is used as an example (downloadable here).

1. Add a symlink from the shared object for your version of the JRE to /usr/lib/libjvm.so. For example:

   ln -s /usr/lib/jvm/java-6-openjdk/jre/lib/amd64/server/libjvm.so /usr/lib/libjvm.so
   

2. Start the build:

   make install USE_PGXS=1
   

Query AlloyDB Data as a PostgreSQL Database

After you have installed the extension, follow the steps below to start executing queries to AlloyDB data:

1. Log into your database.
2. Load the extension for the database:

   CREATE EXTENSION jdbc2_fdw;
   

3. Create a server object for AlloyDB:

   CREATE SERVER AlloyDB 
   FOREIGN DATA WRAPPER jdbc2_fdw OPTIONS (
   drivername 'cdata.jdbc.alloydb.AlloyDBDriver',
   url 'jdbc:alloydb:User=alloydb;Password=admin;Database=alloydb;Server=127.0.0.1;Port=5432',
   querytimeout '15',
   jarfile '/home/MyUser/CData/CData\ JDBC\ Driver\ for\ Salesforce MyDriverEdition/lib/cdata.jdbc.alloydb.jar'); 
   

4. Create a user mapping for the username and password of a user known to the MySQL daemon.

   CREATE USER MAPPING for postgres SERVER AlloyDB OPTIONS (
   username 'admin', 
   password 'test');
   

5. Create a foreign table in your local database:

   postgres=# CREATE FOREIGN TABLE orders (
   orders_id text,
   orders_ShipName text,
   orders_ShipCity numeric) 
   SERVER AlloyDB OPTIONS (
   table_name 'orders');
   

You can now execute read/write commands to AlloyDB:

postgres=# SELECT * FROM orders;