Batch upsert

gistfile1.sql

 WITH
  -- write the new values
 n(ip,visits,clicks) AS (
    VALUES ('192.168.1.1',2,12),
           ('192.168.1.2',6,18),
           ('192.168.1.3',3,4)
 ),
  -- update existing rows
 upsert AS (
    UPDATE page_views o
    SET visits=n.visits, clicks=n.clicks
    FROM n WHERE o.ip = n.ip
    RETURNING o.ip
 )
 -- insert missing rows
 INSERT INTO page_views (ip,visits,clicks)
 SELECT n.ip, n.visits, n.clicks FROM n
 WHERE n.ip NOT IN (
    SELECT ip FROM upsert
 );