Re: BUG #17258: Unexpected results in CHAR(1) data type

> On Oct 29, 2021, at 11:14 AM, PG Bug reporting form <noreply(at)postgresql(dot)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
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