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

Connect to Google Spanner Data as a JDBC Data Source

To connect to Google Spanner 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.googlespanner.GoogleSpannerDriver
  

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

  Google Spanner uses the OAuth authentication standard. To authenticate using OAuth, you can use the embedded credentials or register an app with Google.

  See the Getting Started guide in the CData driver documentation for more information.

  Built-in Connection String Designer

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

  java -jar cdata.jdbc.googlespanner.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:googlespanner:ProjectId='project1';InstanceId='instance1';Database='db1';InitiateOAuth=GETANDREFRESH;
  

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 Google Spanner Data as a PostgreSQL Database

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

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

   CREATE EXTENSION jdbc2_fdw;
   

3. Create a server object for Google Spanner:

   CREATE SERVER GoogleSpanner 
   FOREIGN DATA WRAPPER jdbc2_fdw OPTIONS (
   drivername 'cdata.jdbc.googlespanner.GoogleSpannerDriver',
   url 'jdbc:googlespanner:ProjectId='project1';InstanceId='instance1';Database='db1';InitiateOAuth=GETANDREFRESH;',
   querytimeout '15',
   jarfile '/home/MyUser/CData/CData\ JDBC\ Driver\ for\ Salesforce MyDriverEdition/lib/cdata.jdbc.googlespanner.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 GoogleSpanner OPTIONS (
   username 'admin', 
   password 'test');
   

5. Create a foreign table in your local database:

   postgres=# CREATE FOREIGN TABLE customer (
   customer_id text,
   customer_Name text,
   customer_TotalDue numeric) 
   SERVER GoogleSpanner OPTIONS (
   table_name 'customer');
   

You can now execute read/write commands to Google Spanner:

postgres=# SELECT * FROM customer;