Re: BUG #14800: substring produces different results with similar types

On Wed, Sep 6, 2017 at 10:10 AM, Артём Костин <kostin(dot)artem(at)gmail(dot)com>
wrote:

> I'm sorry for this approach.
>
> The main point is that behaviour are not applied to all character types
> described in docs. You can see it in my example.
>

​There is only one "character type" in PostgreSQL, it is spelled
"character" (char is a valid alias).
​

>
>
> For the second point, please, check chapter 8.3 for this
> "Trailing spaces are removed when converting a character value to one of
> the other string types. Note that trailing spaces are semantically
> significant in character varying and text values, and when using pattern
> matching, that is LIKE and regular expressions."
>
>
IOW, ​The "character" data type is one of three "string-class" types in the
PostgreSQL system. "character" has no concept of "semantically significant
trailing whitespace". Therefore when converting from "character" to one of
the other two "string-class" types (varchar, text) you will never end up
with a resultant value with trailing whitespace.

​David J.