Re: (b)trim anomalies

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
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http://www.sitening.com/
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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(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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