Unable to create oracle_fdw (foreign data wrapper) extension

I am following the instructions here:
http://blog.dbi-services.com/connecting-your-postgresql-instance-to-an-oracle-database/
to install Oracle foreign data wrapper, oracle_fdw, on a PostgreSQL server.

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Oracle version: Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 -
64bit Production, running on Red Hat Linux 7.2

PostgreSQL version: PostgreSQL 9.4.4 on x86_64-unknown-linux-gnu, compiled
by gcc (Debian 4.7.2-5) 4.7.2, 64-bit, running on Debian 7 (wheezy).
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I was able to install sqlplus and connect from PostgreSQL server to Oracle
server using sqlplus successfully, so connectivity is not a problem.

But when I try to create the extension, I get the following error:

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postgres=# create extension oracle_fdw;
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
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Then I took clues from https://github.com/dalibo/pg_qualstats/issues/1 and
added oracle_fdw to shared_preload_libraries in postgresql.conf like this:

shared_preload_libraries = 'oracle_fdw'

but now I can't restart Postgres:

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# service postgresql restart
[....] Restarting PostgreSQL 9.4 database server: main[....] The PostgreSQL
server failed to start. Please check the log output: t=2016-09-15 11:05:42
PDT d= h= p=23300 a=FATAL: XX000: invalid cache ID[FAILt=2016-09-15
11:05:42 PDT d= h= p=23300 a=LOCATION: SearchSysCacheList, syscache.c:1219
... failed!
failed!
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Looking into /var/log/postgresql/postgresql-9.4-main.log I only see these
two lines:

t=2016-09-15 11:05:42 PDT d= h= p=23300 a=FATAL: XX000: invalid cache ID:
41
t=2016-09-15 11:05:42 PDT d= h= p=23300 a=LOCATION: SearchSysCacheList,
syscache.c:1219

Removing oracle_fdw from shared_preload_libraries allows postgres to be
restarted, so this is the one causing restart to fail.

How to fix this and get the foreign data wrapper working?

Thank you.

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