Re: BUG #18051: char(N) and varchar(N) behave opposite to the documentation

On Wednesday, August 9, 2023, PG Bug reporting form <noreply@postgresql.org> wrote:

The following bug has been logged on the website:

Bug reference:      18051
Logged by:          Nicolas Gouteux
Email address:      nicolas.gouteux@sonarsource.com
PostgreSQL version: 13.7
Operating system:   Linux
Description:       

create table if not exists ngx_char  (
   charcol char(10) not null,
   varcharcol varchar(10) not null
 );
truncate table ngx_char;
insert into ngx_char (charcol, varcharcol) values ('A', 'A');
insert into ngx_char (charcol, varcharcol) values ('A    ', 'A   ');
select charcol || 'B', varcharcol || 'C' from ngx_char;
select * from ngx_char where charcol = varcharcol;

Output:

?column?,?column?
AB,AC
AB,A   C

This is very strange! Is it me?

This is working as designed and documented.  The concatenation to text removes the insignificant white space in char.  There is no manipulation of content for varchar.

Just don’t use char.  There is no good reason to deal with its implicit behaviors.

David J.