I am trying to upgrade Magento version 1.4.1 to 1.9 with the stranded process.
1) Clean all your log tables. This will increase the speed of your upgrade
2) Get current database dump of your website.
3) Setup a local environment and restore you CE-1.4 database to a newly created database
4) Create you local.xml on your new CE 1.9 environment.
5) Start the upgrade process by either opening your site in your browser
but I am getting foreign key constraint error in customer and catalog tables during the database upgrade.
Can anyone help me to fix this issue? or any other best way to upgrade the magento version?
I believe the problem is that making such a large leap in versions is not possible in one upgrade.
The answer here has info relevant to upgrading from 1.4.1.1: How to upgrade magento 1.4 1.1 to 1.7.0.2
Specifically:
Database structure has major changes from 1.4.1.1 to 1.4.2 so you need to upgrade first to 1.4.2 then you can upgrade to 1.7.0.2 directly.
I think your best option is to upgrade in smaller steps until you get where you want to be. The last such upgrade I did included the following steps:
1.8 was the goal, but I had to get to 1.4.2.0 and then 1.7.2.0 before I could proceed.
My git log also shows that some additional code patches were required after upgrading to 1.4.2.0. You could probably find more detailed answers if you search for info on upgrading to that specific version.