[Solved]-Postgresql operator class "varchar_pattern_ops" does not accept data type integer

I’m only able to reproduce your error message like so:

denis=# create index test_idx on test (val varchar_pattern_ops);
CREATE INDEX
denis=# alter table test alter val type int using (val::int);
ERROR:  operator class "varchar_pattern_ops" does not accept data type integer

If you’ve a funky index like that, try dropping and recreating it like so:

denis=# drop index test_idx;
DROP INDEX
denis=# create index test_idx on test (val);
CREATE INDEX
denis=# alter table test alter val type int using (val::int);
ALTER TABLE

Related docs:

http://www.postgresql.org/docs/current/static/indexes-opclass.html