Re: Single Byte values

> -----Original Message-----
> From: pgsql-general-owner(at)postgresql(dot)org
> [mailto:pgsql-general-owner(at)postgresql(dot)org]On Behalf Of Manfred Koizar
> Sent: Thursday, April 03, 2003 5:53 PM
> To: Jason Hihn
> Cc: pgsql-general(at)postgresql(dot)org
> Subject: Re: [GENERAL] Single Byte values
>
>
> On Thu, 03 Apr 2003 13:35:24 -0500, Jason Hihn
> <jhihn(at)paytimepayroll(dot)com> wrote:
> >As someone pointed out, CHAR(1) costs 5 bytes.
>
> Jason, you already found out, that char(1) uses
>
> >4 bytes(stored string length) + 1 data in the case of char(1).
>
> All char(n) types are stored on 4 byte boundaries, so char(1) costs up
> to 8 bytes.

Is this true for memory AND disk, or just memory?

> >But in returning to my question, what should I be using for char(1) to
> >char(4) storage?
>
> Instead of char(1) you can use the Postgres specific type "char"
> (*with* the quotes) which only needs one byte.

So I assume use of this is 'safe'? Any degridation on performance?

It appears that this datatype is also array compatible, CREATE TABLE test3(a
"char"[4]); works!

I guess if space is so important, I could also just store
(char[0]<<8|char[1]) into a smallint...

> For char(n) a little toy has been posted to -hackers half a year ago
> (cf. discussion around
> http://archives.postgresql.org/pgsql-hackers/2002-10/msg00501.php)
> Feel free to play around with it. Though I wouldn't take the trouble
> if only a few thousand rows are involved...
>
> Servus
> Manfred
>
>
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