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

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
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