(b)trim anomalies

Started by Thomas F.O'Connellover 21 years ago6 messagesgeneral

tfo@sitening.com

over 21 years ago

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:

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.

-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

Bruce Momjian

bruce@momjian.us

over 21 years ago

In reply to: Thomas F.O'Connell (#1)

Re: (b)trim anomalies

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

Thomas F.O'Connell

tfo@sitening.com

over 21 years ago

In reply to: Bruce Momjian (#2)

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
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:

Show quoted text

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

bruce@momjian.us

over 21 years ago

In reply to: Thomas F.O'Connell (#3)

Re: (b)trim anomalies

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

Thomas F.O'Connell

tfo@sitening.com

over 21 years ago

In reply to: Bruce Momjian (#4)

Re: (b)trim anomalies

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:

Show quoted text

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>

Bruce Momjian

bruce@momjian.us

over 21 years ago

In reply to: Thomas F.O'Connell (#5)

Re: (b)trim anomalies

Thomas F. O'Connell wrote:

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?

It doesn't reveal with \df because we are mapping the ANSI-standard
syntax of TRIM to the Oracle-compatible function of btrim. That
mapping is not something psql can see.

-- 
  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

(b)trim anomalies

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