Jessica Richard wrote:
I am tuning a database created by someone else. I noticed that some column lengths were defined longer than needed. For example, an Id column is holding a stand length of 20 characters but was defined as varchar(255). On some other columns, for example, a Description column is supposed to hold less than 100 characters but defined as text. I am trying to understand the performance impact if a column is over defined in the following cases: 1. char(20) vs varchar(20) 2. varchar(20) vs varchar(255) 3. varchar(255) vs text thanks, Jessica
From the manual - <quote> Tip: There are no performance differences between these three types, apart from increased storage size when using the blank-padded type, and a few extra cycles to check the length when storing into a length-constrained column. While character(n) has performance advantages in some other database systems, it has no such advantages in PostgreSQL. In most situations text or character varying should be used instead. </quote> http://www.postgresql.org/docs/8.3/static/datatype-character.html -- Shane Ambler pgSQL (at) Sheeky (dot) Biz Get Sheeky @ http://Sheeky.Biz
