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

Connect to Alchemy Data as a JDBC Data Source

To connect to Alchemy 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.api.APIDriver
  

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

  Start by setting the Profile connection property to the location of the Alchemy Profile on disk (e.g. C:\profiles\Alchemy.apip). Next, set the ProfileSettings connection property to the connection string for Alchemy (see below).

  Alchemy API Profile Settings

  Alchemy uses API key authentication. The API key is supplied in the request URL path. To obtain an API key:

  1. Sign in to your Alchemy account at https://dashboard.alchemy.com.
  2. Open an existing app or create a new one.
  3. Copy the app's API key from the API Key dialog.

  After obtaining your API key, set the following connection properties:

  • AuthScheme: Set this to APIKey.
  • Network: Optional. The blockchain network slug for NFT API requests (for example, eth-mainnet, base-mainnet, polygon-mainnet). Defaults to eth-mainnet.

  Set the following in the ProfileSettings connection property:

  • APIKey: Set this to your Alchemy app API key.

  Built-in Connection String Designer

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

  
  java -jar cdata.jdbc.api.jar
  

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

  

  A typical JDBC URL is below:

  
  jdbc:api:Profile=C:\profiles\Alchemy.apip;AuthScheme=APIKey;Network=eth-mainnet;ProfileSettings='APIKey=your_api_key';
  

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 Alchemy Data as a PostgreSQL Database

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

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

   
   CREATE EXTENSION jdbc2_fdw;
   

3. Create a server object for Alchemy:

   
   CREATE SERVER API 
   FOREIGN DATA WRAPPER jdbc2_fdw OPTIONS (
   drivername 'cdata.jdbc.api.APIDriver',
   url 'jdbc:api:Profile=C:\profiles\Alchemy.apip;AuthScheme=APIKey;Network=eth-mainnet;ProfileSettings='APIKey=your_api_key';',
   querytimeout '15',
   jarfile '/home/MyUser/CData/CData\ JDBC\ Driver\ for\ Salesforce MyDriverEdition/lib/cdata.jdbc.api.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 API OPTIONS (
   username 'admin', 
   password 'test');
   

5. Create a foreign table in your local database:

   
   postgres=# CREATE FOREIGN TABLE contractsforowner (
   contractsforowner_id text,
   contractsforowner_Address text,
   contractsforowner_Name numeric) 
   SERVER API OPTIONS (
   table_name 'contractsforowner');
   

postgres=# SELECT * FROM contractsforowner;