Re: (b)trim anomalies - Mailing list pgsql-general

OK, I have documented that the second parameter to btrim() is optional,
and default to a space.  Patch attached and applied.

---------------------------------------------------------------------------

Thomas F. O'Connell wrote:
> Not entirely.
>
> Per <http://www.postgresql.org/docs/7.4/static/functions-string.html>,
> btrim is documented as taking two arguments. There is a single-argument
> version that exists that trims whitespace if only the first argument is
> given (i.e., the characters to trim are omitted). This latter version
> is nowhere documented as far as I can tell.
>
> I'm also curious why, despite its place in the ANSI standard, \df seems
> to reveal no information about trim.
>
> -tfo
>
> --
> Thomas F. O'Connell
> Co-Founder, Information Architect
> Sitening, LLC
> http://www.sitening.com/
> 110 30th Avenue North, Suite 6
> Nashville, TN 37203-6320
> 615-260-0005
>
> On Nov 27, 2004, at 9:23 PM, Bruce Momjian wrote:
>
> > Thomas F.O'Connell wrote:
> >> I was just wondering why the btrim syntax that takes only a single
> >> argument is not documented in 9.4 in the documentation (I checked both
> >> 7.4 and 8.0 docs).
> >>
> >> This is in a 7.4.5 installation:
> >>
> >> pg=# \df btrim
> >>                        List of functions
> >>   Result data type |   Schema   | Name  | Argument data types
> >> ------------------+------------+-------+---------------------
> >>   bytea            | pg_catalog | btrim | bytea, bytea
> >>   text             | pg_catalog | btrim | text
> >>   text             | pg_catalog | btrim | text, text
> >> (3 rows)
> >>
> >> Is it ever documented anywhere that the single-argument version of
> >> btrim can be used to remove whitespace from the left and right of a
> >> given string? Is this version not supposed to be user-facing for some
> >> reason?
> >>
> >> Also, in this post:
> >>
> >> http://archives.postgresql.org/pgsql-sql/2002-01/msg00053.php
> >>
> >> Bruce sort of explains that TRIM is an ANSI word but doesn't fully
> >> explain why it doesn't show up in a \df listing:
> >>
> >> pg=# \df trim
> >>                     List of functions
> >>   Result data type | Schema | Name | Argument data types
> >> ------------------+--------+------+---------------------
> >> (0 rows)
> >>
> >> This one's more a curiosity thing.
> >
> > Because TRIM is an ANSI standard, we document TRIM (BOTH, ...) but not
> > btrim.  The parser does the translation:
> >
> >             | TRIM '(' BOTH trim_list ')'
> >                 {
> >                     /* various trim expressions are defined in SQL92
> >                      * - thomas 1997-07-19
> >                      */
> >                     FuncCall *n = makeNode(FuncCall);
> >                     n->funcname = SystemFuncName("btrim");
> >                     n->args = $4;
> >                     n->agg_star = FALSE;
> >                     n->agg_distinct = FALSE;
> >                     $$ = (Node *)n;
> >
> > Does that answer your questions?
> >
> > --
> >   Bruce Momjian                        |  http://candle.pha.pa.us
> >   pgman@candle.pha.pa.us               |  (610) 359-1001
> >   +  If your life is a hard drive,     |  13 Roberts Road
> >   +  Christ can be your backup.        |  Newtown Square, Pennsylvania
> > 19073
>

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073
Index: doc/src/sgml/func.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/func.sgml,v
retrieving revision 1.225
diff -c -c -r1.225 func.sgml
*** doc/src/sgml/func.sgml    1 Dec 2004 19:32:12 -0000    1.225
--- doc/src/sgml/func.sgml    2 Dec 2004 17:12:57 -0000
***************
*** 1070,1081 ****
        </row>

        <row>
!        <entry><literal><function>btrim</function>(<parameter>string</parameter> <type>text</type>,
<parameter>characters</parameter><type>text</type>)</literal></entry> 
         <entry><type>text</type></entry>
         <entry>
          Remove the longest string consisting only of characters
!         in <parameter>characters</parameter> from the start and end of
!         <parameter>string</parameter>.
         </entry>
         <entry><literal>btrim('xyxtrimyyx', 'xy')</literal></entry>
         <entry><literal>trim</literal></entry>
--- 1070,1082 ----
        </row>

        <row>
!        <entry><literal><function>btrim</function>(<parameter>string</parameter> <type>text</type>
!        <optional>, <parameter>characters</parameter> <type>text</type></optional>)</literal></entry>
         <entry><type>text</type></entry>
         <entry>
          Remove the longest string consisting only of characters
!         in <parameter>characters</parameter> (or spaces if not supplied)
!         from the start and end of <parameter>string</parameter>.
         </entry>
         <entry><literal>btrim('xyxtrimyyx', 'xy')</literal></entry>
         <entry><literal>trim</literal></entry>