Re: zero char is returned as space

[Konstantin Izmailov]

Tom,
thank you very much! It makes sense now.

K

On Tue, Apr 5, 2022 at 10:08 PM Tom Lane  wrote:

> Konstantin Izmailov  writes:
> > could you help me understand if this is an intended behaviour, or I'm
> > incorrectly querying a "char" field?
>
> We do not support '\0' as an element of a string value.  You didn't
> show how you're trying to insert this value, but I suspect that
> Postgres saw it as an empty string which it then space-padded to
> length 1 because that's what char(1) does.
>
> Don't use a string field to store an integer.  What with the need
> for a length header, you wouldn't be saving any space compared to
> "smallint" even if there weren't any semantic issues.
>
> regards, tom lane
>

zero char is returned as space

[Konstantin Izmailov]

Hi,
could you help me understand if this is an intended behaviour, or I'm
incorrectly querying a "char" field? I have simple table with column
declared as:
  c_tinyint char NOT NULL

The column contains tiny integers in range 0-10. When I query the column
from my app using libpq values 1-10 are returned correctly as 0x1-0x10. But
value of zero is returned as 0x20 (expected 0x0).
The pgAdmin displays result of the query
SELECT c_tinyint, ascii(c_tinyint) FROM tbl
as shown below:
| c_tinyint   | ascii |
| character(1) | integer |
| |  0 |
| |  1 |
| |  2 |
| |  3 |
| |  4 |

Thank you
K