Table column with duplicated text values

Question

I have a database table where a have a varchar(200) column.
This is a table with historical log information where about 99.9% of the rows in the table contains the same text message as another row in the table.
The size of that database and speed when searching is becoming a problem.

So I was thinking that I could move the varchar values to another table with unique text values and then have a reference to that table for every row in the first table, but before I change this, I would like to know if there is an easier way to do this?
For instance setting some property on my existing table column that would cause this behavior automatically. So that the database automatically maintains a table with unique texts. I realize that this would of cause have a big performance impact on delete operation but that is almost never done anyway. Also I would really like to avoid changing the program that inserts into the log table.

I have been using MySQL but if another DB can do this it is also an option to change the database another one. (MariaDB or other?)

Thanks

Answer 1

There is no property or whatsoever that handles this for you, but you have a good idea there, putting the varchar data in a separate table. To do so, follow these steps.

1. Create your table holding your varchar data like this:

   CREATE TABLE log_messages (id int auto_increment primary key, message varchar(200)) ENGINE = MyISAM ROW_FORMAT=FIXED;

2. Insert your varchar data

   INSERT INTO log_messages (message) SELECT DISTINCT your_varchar_column FROM your_table;

3. Add a new column in your original table to reference the new log_messages table

   ALTER TABLE your_table ADD COLUMN message_id int not null;

4. Create the reference

   UPDATE your_table y INNER JOIN log_messages m ON y.your_varchar_column = m.message SET y.message_id = m.id;

5. Then you can drop the varchar column from your table

   ALTER TABLE your_table DROP COLUMN your_varchar_column;

Now that you have that, I'm not sure why you're concerned about performance impact on delete operations. There's none.

Answer 2

This is the right way to do normalisation, but my advice is instead of unique text go for number(integer).....