PostgreSQL: Defining a primary key on a large database

Question

I am planing a database to store lots of text. (blog posts, news articles, etc.) The database needs to have the title, content (50k characters max), date, link and language

Answer 1

Hashes are bad ideas for primary keys. They make the inserts end up in random order in the table, and that gets very costly as things have to be reallocated (though Postgres doesn't really apply that the way others do). I suggest a sequential primary key which may be a fine-grained timestamp / timestamp with sequential number following, letting you kill two birds with a stone, and a second unique index that contains your hash codes. Keep in mind you want to keep your primary key as a smaller (64 bit or less) column.

See the table at http://en.wikipedia.org/wiki/Birthday_attack#The_mathematics so you can be confident you won't have a collision.

Don't forget to vacuum.