<database>=# create extension rum;
ERROR:  operator % already exists
<database>=# select version();
                                                                   version
---------------------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 11.5 (Ubuntu 11.5-1.pgdg16.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609, 64-bit

<database>=# \dx
                                                                     List of installed extensions
         Name         | Version |     Schema     |                                                     Description
----------------------+---------+----------------+---------------------------------------------------------------------------------------------------------------------
 address_standardizer | 2.4.7   | public         | Used to parse an address into constituent elements. Generally used to support geocoding address normalization step.
 adminpack            | 2.0     | pg_catalog     | administrative functions for PostgreSQL
 aggs_for_arrays      | 1.3.2   | public         | Various functions for computing statistics on arrays of numbers
 aggs_for_vecs        | 1.2.1   | public         | Various functions for computing statistics on vectors (arrays) of numbers
 btree_gin            | 1.3     | public         | support for indexing common datatypes in GIN
 btree_gist           | 1.5     | public         | support for indexing common datatypes in GiST
 cstore_fdw           | 1.6     | public         | foreign-data wrapper for flat cstore access
 cube                 | 1.4     | public         | data type for multidimensional cubes
 dblink               | 1.2     | public         | connect to other PostgreSQL databases from within a database
 file_fdw             | 1.0     | public         | foreign-data wrapper for flat file access
 floatvec             | 1.0.1   | public         | Math for vectors (arrays) of numbers
 hll                  | 2.12    | public         | type for storing hyperloglog data
 http                 | 1.3     | public         | HTTP client for PostgreSQL, allows web page retrieval inside the database.
 madlib               | 1.16.0  | madlib         | A scalable in-database analytics library
 multicorn            | 1.3.4   | public         | Multicorn Python bindings for Postgres 9.2.* Foreign Data Wrapper
 pg_buffercache       | 1.3     | public         | examine the shared buffer cache
 pg_cron              | 1.1     | public         | Job scheduler for PostgreSQL
 pg_similarity        | 1.0     | public         | support similarity queries
 pg_stat_statements   | 1.6     | public         | track execution statistics of all SQL statements executed
 pg_trgm              | 1.4     | public         | text similarity measurement and index searching based on trigrams
 pgl_ddl_deploy       | 1.6     | pgl_ddl_deploy | automated ddl deployment using pglogical
 pglogical            | 2.2.2   | pglogical      | PostgreSQL Logical Replication
 pgstattuple          | 1.5     | public         | show tuple-level statistics
 plpgsql              | 1.0     | pg_catalog     | PL/pgSQL procedural language
 plpython2u           | 1.0     | pg_catalog     | PL/Python2U untrusted procedural language
 plpython3u           | 1.0     | pg_catalog     | PL/Python3U untrusted procedural language
 plpythonu            | 1.0     | pg_catalog     | PL/PythonU untrusted procedural language
 pltclu               | 1.0     | pg_catalog     | PL/TclU untrusted procedural language
 postal               | 1.0     | public         | Postal address normalizer.
 postgis              | 2.4.7   | postgis        | PostGIS geometry, geography, and raster spatial types and functions
 quantile             | 1.1.5   | public         | Provides quantile aggregate function.
 smlar                | 1.0     | public         | compute similary of any one-dimensional arrays
 tsm_system_time      | 1.0     | public         | TABLESAMPLE method which accepts time in milliseconds as a limit