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

Nice. Thanks, Bruce. If I felt as if I could speak a little more
authoritatively about why it had been missing, I would've offered to
document it.

Now it is a psql/postgres internals issue that causes \df trim not to
reveal anything?

-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 Dec 2, 2004, at 11:14 AM, Bruce Momjian wrote:

> 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>