> On Oct 29, 2021, at 11:14 AM, PG Bug reporting form <noreply@postgresql.org> wrote:
>
> select length(substr(' '::varchar,1,1)), ascii(substr('
> '::varchar,1,1));
> produces==> 1 32 (as expected)
>
> select length(substr(' '::char,1,1)), ascii(substr(' '::char,1,1));
> produces==> 0 0 (not as expected)
There are four substr() functions defined in the standard distribution. They are:
substr(text, int4, int4)
substr(text, int4)
substr(bytea, int4, int4)
substr(bytea, int4)
There is none defined directly for char(n). Since "text" is the preferred type (not "bytea"), I expect a cast of your
''::char to text before entry to the function. So the question is why casting ' '::char to text is different than '
'::text. The answer is that cast is implemented using rtrim1, which trims trailing space.
—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company