Re: Document that char () ignores spaces only in non-patterncomparisons

Kevin Grittner wrote:
> Bruce Momjian <bruce@momjian.us> wrote:
>
> > A private email I received indicated that our documentation about
> > ignoring trailing spaces in CHAR() comparisons was slightly
> > inaccurate.  I have update our docs to indicate it is only
> > non-pattern comparisons that ignore spaces with CHAR().  Applied
> > doc patch attached.
>
> This language:
>
> | disregarded when non-pattern comparing two values
>
> seems quite awkward.

Yes, it is.  :-(

Oh, I wanted to show an example of the difference:

    test=> SELECT 'abc'::char(4) = 'abc'::char(6);
     ?column?
    ----------
     t
    (1 row)

    test=> SELECT 'abc'::char(4) LIKE 'abc'::char(6);
     ?column?
    ----------
     f
    (1 row)

> Isn't it a stretch to consider pattern-matching predicates to be
> compares, anyway?  It seems like it would be better to distinguish
> between comparisons, where the trailing spaces are ignored, and
> other predicates such as pattern matching, where trailing spaces are
> not ignored.

Uh, how about I remove "pattern" from the first sentence, but keep the
second pattern mention and remove the word "comparison" there?

    treated as semantically insignificant.  Trailing spaces are
--> disregarded when comparing two values of type <type>character</type>,
    and they will be removed when converting a <type>character</type> value
    to one of the other string types.  Note that trailing spaces
    <emphasis>are</> semantically significant in
    <type>character varying</type> and <type>text</type> values, and
--> when using pattern matching, e.g. <literal>LIKE</>,
    regular expressions.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +