correct NULL to INT_MIN
Merge branch 'piggyback_master' of https://github.com/mpws2013n1/postgres into piggyback_master
Merge branch 'piggyback_master' of https://github.com/mpws2013n1/postgres into piggyback_master
Merge branch 'piggyback_master' of https://github.com/mpws2013n1/postgres into piggyback_master