length of string containing blanks is 0, || behaves differently than concat on string of blanks

Hi,

I am not sure, if this is a bug. I think at least it is a documentation bug.
I would expect for concat and || to yield the same results, as long as no NULL is involved. But in my case when I concat a letter and a string of blanks, the results differ.
Is it a bug or is this a feature (then please point me to the documentation, because I could not find it)?

Steps to reproduce:
drop table blubb;
create table blubb (text1 character(3), text2 character(1));
insert into blubb (text1, text2) values (' ', 'a');
commit;

prod5=> select concat('#',text1,'#'), length(text1), text2 from blubb;
concat | length | text2
--------+--------+-------
# # | 0 | a
(1 row)

The string contains three blanks. Its length should be 3 to my understanding.

prod5=> select * from blubb where concat(text1, text2) = ' a';
text1 | text2
-------+-------
| a
(1 row)

This is what I expect.

prod5=> select * from blubb where text1||text2 = ' a';
text1 | text2
-------+-------
(0 rows)

Now, this comes unexpected. According to documentation || should concatenate both strings, giving the same result as concat above.

Regards,

Sigrid Ehrenreich
Dipl.-Informatikerin
Senior Consultant

Consist Software Solutions GmbH
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