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Postgres foreign data wrapper for Oracle (oracle_fdw) on MacOS

The Ecto adapter landscape currently lacks an Oracle option. If you’re itching to try out Elixir and/or Phoenix but really need to connect to an Oracle database to do anything interesting, you may want to give Laurenz Albe’s oracle_fdw project a try. oracle_fdw implements a foreign data wrapper for Postgres that allows you to connect to, read from, and manipulate remote Oracle databases.

Oracle_fdw relies on DYLD_LIBRARY_PATH to properly link Oracle libraries at runtime, but MacOS version 10.11 (El Capitan) and newer ignore DYLD_LIBRARY_PATH as part of its System Integrity Protection (SIP) feature. These steps will help you both build and install oracle_fdw on MacOS.

1. Install Postgres

The easiest way to install Postgres is homebrew: brew install postgres. Once installed it can be started with brew services start postgres.

2. Install instantclient

Download an instantclient from Oracle. You’ll need both the basic package and the SDK package. Out of the box, oracle_fdw expects that you’ll be using version 11.2. If you want to use 12.1, you’ll need to create some symlinks to trick it.

I install my instant client in ~/lib/instantclient_11_2. You can install yours wherever you like—just be sure that you expose an environment variable called ORACLE_HOME that points to your installation.

3. Build oracle_fdw

Download the latest release of oracle_fdw and unpack it. cd into the unpacked directory and compile the extension with make.

Once oracle_fdw is compiled, you have two options for proceeding: modify the compiled binary or symlink your instantclient to a location it can find. Without doing one of these, you’ll likely encounter this error upon loading the extension in Postgres:

ERROR:  could not load library "/usr/local/lib/postgresql/oracle_fdw.so":
  dlopen(/usr/local/lib/postgresql/oracle_fdw.so, 10):
  Library not loaded: @rpath/libclntsh.dylib.11.1
  Referenced from: /usr/local/lib/postgresql/oracle_fdw.so
  Reason: image not found

Option 1: alter the oracle_fdw binary

This is the option I chose. It lets me tweak the compiled binary while leaving everything else as-is. After compiling with make (and before make install), issue this command:

install_name_tool -add_rpath $ORACLE_HOME oracle_fdw.so

This adds your ORACLE_HOME path to the list of rpaths in oracle_fdw.so.

The other option is to symlink libclntsh.dylib.11.1 to one of the default search paths, ~/lib:

ln -s $ORACLE_HOME/libclntsh.dylib.11.1 ~/lib/

4. Install oracle_fdw

Now that oracle_fdw is compiled and ready to link up the instantclient, install it and its friends with make install.

At this point you should be able to fire up your favorite Postgres client and enable the extension with this SQL:

CREATE EXTENSION oracle_fdw;

If you don’t see any gnarly errors, you’re in business! I’ll write up another post soon that demonstrates how to use the extension.

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