Re: best practices with index on varchar column

On Wed, 23 Mar 2005 12:11:56 +0800, Michael Ryan S. Puncia
<mpuncia(at)census(dot)gov(dot)ph> wrote:
>
> I have an experience using LIKE in a VARCHAR column and select statement
> suffers a lot so I decided to go back in CHAR
>
> Note: my database has about 50 millions records a b tree index

Strange...

According to the PostgreSQL's documentation:

Tip: There are no performance differences between these three types,
apart from the increased storage size when using the blank-padded type.
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.

To my best knowledge char and varchar are stored in a same way
(4-byte length plus textual value), so using char should make tables
bigger in your case. Then again, having each row exactly the same
size makes it easier to delete and then later insert a new row in
a same spot. Am I thinking correct? Is it a case where using char(n)
makes that table avoid hmm fragmentation of some sort?

Regards,
Dawid