gv2=> SELECT userid,
       COUNT(ALL version_identifier LIKE '%ios%'),
       COUNT(ALL version_identifier LIKE '%android%')
FROM gl.user_device
GROUP BY userid;
                userid                | count | count
--------------------------------------+-------+-------
 46d0f5b7-42b0-4aad-9162-1390c32cb06e |     7 |     7
 5d519794-abfe-4863-82d4-6da33db7637b |     7 |     7
 a81cff6b-30f2-4b6e-a5bf-b1a933904473 |     1 |     1
 b65f0708-0cd1-11e7-878b-06fa189da46b |     4 |     4
 94b91b02-ff43-4a9a-b317-037fa2a347d3 |     1 |     1
 a4cacd98-1216-4801-b058-b28b8fa632a9 |     8 |     8
(6 rows)

gv2=> SELECT userid FROM gl.user_device WHERE version_identifier LIKE '%ios%';
                userid
--------------------------------------
 5d519794-abfe-4863-82d4-6da33db7637b
(1 row)

SELECT userid,
       COUNT(CASE WHEN version_identifier like '%ios%' THEN 1 END) as nr_ios,
       COUNT(CASE WHEN version_identifier like '%android%' THEN 1 END) as nr_android
FROM gl.user_device
GROUP BY userid;

SELECT userid,
       COUNT(*) FILTER (WHERE version_identifier LIKE '%ios%') AS nr_ios,
       COUNT(*) FILTER (WHERE version_identifier LIKE '%android%') AS nr_android
FROM   gl.user_device
GROUP  BY userid;

SELECT userid
     , COALESCE(nr_ios    , 0) AS nr_ios
     , COALESCE(nr_android, 0) AS nr_android
FROM  (
   SELECT userid, COUNT(*) AS nr_ios
   FROM   gl.user_device
   WHERE  version_identifier LIKE '%ios%'
   GROUP  BY 1
   ) i
FULL JOIN (
   SELECT userid, COUNT(*) AS nr_android
   FROM   gl.user_device
   WHERE  version_identifier LIKE '%android%'
   GROUP  BY 1
   ) a USING (userid);