PostgreSQL Discussion - About column type to "varchar(1)" or "char(1)"

Author

About column type to "varchar(1)" or "char(1)"

Emi Lu

2005-08-24, 8:24 pm

Good afternoon,

A question about varchar(1) and char(1).
If we have two tables
test1 (col1 varchar(1), ... ... );
test2 (col1 char(1), ... ... );

In the manuall, it written:

*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.

As a result, setup 'col1' to either "varchar(1)" or "char(1)" does not
matter at all?

Thanks a lot,
Emi

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TIP 2: Don't 'kill -9' the postmaster

Martijn van Oosterhout

2005-08-24, 8:24 pm

On Wed, Aug 24, 2005 at 03:06:18PM -0400, Emi Lu wrote:
> Good afternoon,
>
> A question about varchar(1) and char(1).

<snip>

> As a result, setup 'col1' to either "varchar(1)" or "char(1)" does not
> matter at all?

As far as storage goes, nope. Think about it, depending on your
encoding, 1 character might be 4 bytes.

char() adds padding but varchar() doesn't. That's the difference
really...

Hope this helps,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.

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