When you have a TEXT field in MySQL or PostgreSQL, should you put it in a separate table?

Question

I\'ve heard that if you have a table with a TEXT column that will hold a large chunk of text data, it\'s better for performance to move that column into a separate table and

Answer 1

In some scenarios, this might be true. The reason is that let's say your table is:

create table foo (
    id serial primary key,
    title varchar(200) not null,
    pub_date datetime not null,
    text_content text
);

Then you do a query like this:

select id, title, pub_date
  from foo;

You will have to load much more pages from disk that you would have if you didn't have the text_content field in that table. And query optimization is most about reducing disk I/O to the minimum possible.