New version of Wordpress with old DB

Question

First of all I am asking the question here because I did not get an answer in the wordpress forum.

I have a working blog based on wordpress 3.8 , which is a pretty old version. I would like to start everything from scratch and to use the existing DB with all the data (which is very very big, 300+ thousands of tables, it is multisite).

I am afraid to upgrade it because I suspect that the core files were modified in the past (before me).

I would like to install the most recent version of wordpress and make sure everything is compatible and working. What is the best method to do so?

I can install the most recent version and connect it to a clone of the old db instance. Can it break something?

I can install a clean version 3.8 and perform an upgrade. Is it a smart thing to do?

Other methods?

Answer 1

Step 1: backup your database.
Step 2: backup your code base.
Step 3: In a non-production installation, upgrade the WordPress installation. This will trigger a database upgrade as WP needs.

At this point, you have a backup of the old data, you have a versioned copy of the data, and you have a copy of the code that may have been modified, as well as a version that is "current / correct". You are in a position of strength to test functionality, ensure nothing has been lost, etc.

If everything looks good, you could then upgrade the production installation (keeping a copy of backups of both the database and the code base).

Lastly, if I were in your shoes, I would visit the Release Archive and download the specific version you are currently on (3.8.?), then run a comparison between the known good / unaltered files and the files that you have in place. In this way, you can prove whether core files had been altered, and you can see the alterations. This would provide you with the information you might need to re-implement those "features" that were incorrectly implemented in the core code.