http://stackoverflow.com/questions/15982588/hdbc-odbc-mysql-query-only-fails-when-compiled

dbtest.hs

import Database.HDBC
import Database.HDBC.MySQL as MySQL

-- Test code based on a stackoverflow question:
--   http://stackoverflow.com/questions/15982588/hdbc-odbc-mysql-query-only-fails-when-compiled
-- Original code is here:
--   http://pastebin.com/9vrStfs7
-- Test Environments:
--   CPU: Core i7-3770
--   OS:  Linux 3.8.5
--   GHC: 7.6.2
--   HDBC-mysql: 0.6.6.1

connectDatabase :: IO MySQL.Connection
connectDatabase = connectMySQL defaultMySQLConnectInfo
                  { mysqlHost = "127.0.0.1" , mysqlUser = "osak", mysqlPassword = "test", mysqlDatabase = "test", mysqlPort = 3306, mysqlUnixSocket = "/var/run/mysqld/mysqld.sock" }

main = do
    nativeconn <- connectDatabase
    test6 nativeconn
    
putShow = putStrLn . show

-- runghc:  prints "0"
-- ghc -O2: SqlError
test1 conn = run conn "CREATE OR REPLACE VIEW user_usergroup_map AS SELECT * FROM users" [] >>= putShow

-- runghc:  prints nothing
-- ghc -O2: prints nothing
test2 conn = seq (run conn "CREATE OR REPLACE VIEW user_usergroup_map AS SELECT * FROM users" [] >>= putShow) (return ())

-- runghc:  prints "0"
-- ghc -O2: SqlError
test3 conn = do
  rows <- run conn "CREATE OR REPLACE VIEW user_usergroup_map AS SELECT * FROM users" []
  putShow rows

-- runghc:  nothing happens
-- ghc -O2: nothing happens
test4 conn = do
  run conn "INSERT INTO users (name) VALUES ('osak')" []

-- runghc:  1 entry inserted
-- ghc -O2: raises SqlError but insert was succeeded
test5 conn = do
  run conn "INSERT INTO users (name) VALUES ('osak')" []
  commit conn

-- runghc:  nothing happens
-- ghc -O2: nothing happens
test6 conn = do
  (run conn "INSERT INTO users (name) VALUES ('osak')" []) `seq` (commit conn)