問題：
1. 分析PostGreSql源碼應該從那裏入手？
command:
pg_ctlcluster
[Stop postgre database 8.4]
pg_ctlcluster 8.4 main stop
[Open postgre database 9.0]
su - postgres
/usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data
/usr/local/pgsql/bin/postgres -D /usr/local/pgsql/data >logfile 2>&1 &
/usr/local/pgsql/bin/createdb test
/usr/local/pgsql/bin/psql test
[other]
/usr/local/pgsql/bin/pg_ctl -D /usr/local/pgsql/data stop
/usr/local/pgsql/bin/pg_ctl -D /usr/local/pgsql/data reload
