switching from Sqlite3 to PostgreSQL on an existing rails application -

when tried switching sqlite3 postgresql in existing application faced problem rake db:migrate, did following

1 - rake db:create

2- rake db:migrate got error:

== addcolumn1: migrating ===================================================== -- add_column(:users, :first_name, :string) rake aborted! error has occurred, , later migrations canceled: pg::error: error: relation "users" not exist

3- rake db:reset

4- rake db:migrate , migration done no errors

i have lost data specially admin user because of rake db:reset , questions :

1- why forced use rake db:reset ?

2- there ways transfer data database engine without losing in next time ?

3- , postgresql couldn’t use blank password , said fe_sendauth: no password supplied , after adding password error gone , using password in database engine instead of sqlite3 must ?

4- heroku require reset or github accept data if use db engine in development ?

this railscast great resource on migrating, , should answer of questions:

http://railscasts.com/episodes/342-migrating-to-postgresql