extensions-installed

# Extensions installed on server

SELECT name, default_version, installed_version, left(comment,30) As comment
FROM pg_available_extensions
WHERE installed_version IS NOT NULL
ORDER BY name;

# Output example:

name | def | installed | com
---------------+-------+-----------+--------------------------------------------
btree_gist | 1.0 | 1.0 | support for indexing common datatypes in..
fuzzystrmatch | 1.0 | 1.0 | determine similarities and distance betw..
hstore | 1.2 | 1.2 | data type for storing sets of (key, valu..
plpgsql | 1.0 | 1.0 | PL/pgSQL procedural language..
plv8 | 1.3.0 | 1.3.0 | PL/JavaScript (v8) trusted procedural la..
postgis | 2.1.3 | 2.1.3 | PostGIS geometry, geography, and raster ..
www_fdw | 0.1.8 | 0.1.8 | WWW FDW - extension for handling differe..

#To get more details about a particular extension already installed on your server, enter
#the following command from psql:

\dx+ fuzzystrmatch

#Alternatively, execute the following query:

SELECT pg_catalog.pg_describe_object(d.classid, d.objid, 0) AS description
FROM pg_catalog.pg_depend AS D INNER JOIN pg_catalog.pg_extension AS E
ON D.refobjid = E.oid
WHERE D.refclassid = 'pg_catalog.pg_extension'::pg_catalog.regclass AND deptype
= 'e' AND E.extname = 'fuzzystrmatch';

# This shows what’s packaged in the extension:
# Output example:

description
----------------------------------------------------------------------------
function dmetaphone_alt(text)
function dmetaphone(text)
function difference(text,text)
function text_soundex(text)
function soundex(text)
function metaphone(text,integer)
function levenshtein_less_equal(text,text,integer,integer,integer,integer)
function levenshtein_less_equal(text,text,integer)
function levenshtein(text,text,integer,integer,integer)
function levenshtein(text,text)