Refactoring a MySQL database

First nerdy post here. If you’re anything like me, you’ve found yourself having to refactor your MySQL database more than once. In my case, every time I’ve re-IP’d my local network I have had to do this. This is because I’m using a MySQL database to maintain a synchronized list of media files across multiple instances of Kodi. Maybe that’ll be another post, but since I’ve had to do this more than once I figured I’d try to share this somewhere, if only for my own benefit.

Way back when I had used Python to tie into a MySQL database. I was “comfortable” with this at that time, so I chose Python as my language of choice.

Problem

The main problem that had to be solved was that the database points to a hard-coded local IP. This means that if I want to change my server’s IP from 192.168.1.10 to 192.168.2.10, I have to modify the database manually if I don’t want to lose anything.

Now, Kodi has an interesting¬†database structure. The only thing to really take from that is that everything seems to point back to the main table “path”. Specifically the idPath / strPath pair. Notice that the strPath, below, has the hard-coded IP that I was mentioning. The goal is to change every entry in that table from “192.168.1.10” to “192.168.2.10”

Solution

Enter Python: There is a mysql.connector class that allows one to interact with MySQL from Python.

import mysql.connector

From here, you can connect to the database using your known database address, user name and password:

cnx = mysql.connector.connect(user='username', password='password', host='127.0.0.1', database='MyVideos107')

Now, the thing that I’m most concerned about is the strPath and the idPath. Since I know that idPath will be unique (… it is a database key) I can just select the two columns, refactor the string, and update each entry. First for the selection:

query='SELECT idPath, strPath FROM path'
cursor = cnx.cursor(buffered=True)
cursor.execute(query)

At this point, cursor has every entry of the ‘path’ table. The next thing to do is loop over every entry. Python’s loop syntax can be burdensome, but useful once figured out:

for (idPath, strPath) in cursor:

The next steps of refactoring and replacing are done in a single line of code – well two lines of code but still… Currently this is all in the for loop, but there’s no reason UpdateQuery2 couldn’t be placed in front of everything.

 UpdateQuery2="UPDATE path SET strPath=%s WHERE idPath=%s"
 cursor2.execute(UpdateQuery2, (strPath.replace('192.168.1.10','192.168.2.10'), idPath))

At this point, everything is buffered in the cursor2 object. I left the instantiation out earlier for simplicity, but will show it later. Once the loop is complete, the last thing to do is commit the transaction of cursor2:

cnx.commit()

After running this within Python I went back and looked at the path database and to my delight, everything was updated to the new IP address. I went back to Kodi and almost everything worked. (See improvement suggestions below)

Code

import mysql.connector

cnx = mysql.connector.connect(user='username', password='password', host='127.0.0.1', database='MyVideos107')

query='SELECT idPath, strPath FROM path'

cursor = cnx.cursor(buffered=True)
cursor2 = cnx.cursor()

cursor.execute(query)

for (idPath, strPath) in cursor:
 UpdateQuery2="UPDATE path SET strPath=%s WHERE idPath=%s"
 cursor2.execute(UpdateQuery2, (strPath.replace('192.168.1.10','192.168.2.10'), idPath))

cnx.commit()

Improvements

It’d be nice to be able to further automate this. For example, most versions of Kodi come out with an updated set of tables. It’d be nice to make this script smart enough to sweep through all of those.

Also, there are actually a number of tables where the static IP gets used – specifically the “art” table and “MyMusic” databases. The first step would be to make the above code allow input arguments of database name, key name, and string field name.¬† Then a list of these values could be looped over to update everything.

Fortunately for me, this is somewhat of a rare occurrence. I re-IP’d when I decided to make a more logical allocation of DHCP reservations. I then had to re-IP in order to allow a graceful VPN into 192.168.1.X networks. So, hopefully I’ll never have to run this again. If I do, I’ll probably make those improvements.

Leave a Reply

Your email address will not be published. Required fields are marked *