Re: pg_attribute.attlen -1 for varchar e pbchar fields

On Mon, Jun 27, 2005 at 02:27:41PM -0300, jimmy.olsen wrote:
>
> SELECT attname, atttypid, attlen
> FROM pg_attribute
> where atttypid IN(1042, 1043)
>
> The attlen column always returns -1 for bpchar and varchar columns. the
> postgre version is 8.0.1. When I look the tables in pgAdmin the column
> lengths are correct. Where can I find the correct column lengths??

See the atttypmod column or the format_type() function:

CREATE TABLE foo (
col_char_1 char(1),
col_char_5 char(5),
col_varchar_10 varchar(10),
col_text text
);

SELECT attname, attlen, atttypmod, format_type(atttypid, atttypmod)
FROM pg_attribute
WHERE attrelid = 'foo'::regclass AND attnum > 0;

attname | attlen | atttypmod | format_type
----------------+--------+-----------+-----------------------
col_char_1 | -1 | 5 | character(1)
col_char_5 | -1 | 9 | character(5)
col_varchar_10 | -1 | 14 | character varying(10)
col_text | -1 | -1 | text
(4 rows)

Notice that atttypmod is 4 greater than the declared length;
presumably the difference is due to the varlena header (the 32-bit
integer that stores the data length). However, that's getting a
little close to internals, so you might want to stick with calling
format_type().

BTW, it's "PostgreSQL" or "Postgres," not "Postgre."

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/