From lsliang@pconline.com.cn Tue Sep  6 02:53:07 2011
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Date: Tue, 6 Sep 2011 10:43:57 +0800
From: "lsliang" <lsliang@pconline.com.cn>
To: "pgsql-docs" <pgsql-docs@postgresql.org>
Subject: about  value  storage   
Message-ID: <201109061043572514728@pconline.com.cn>
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http://www.postgresql.org/docs/9.0/interactive/typeconv-query.html 

example shows: 

CREATE TABLE vv (v character(20));
INSERT INTO vv SELECT 'abc' || 'def';
SELECT v, length(v) FROM vv;

          v           | length
----------------------+--------
 abcdef               |     20
(1 row)


but  my test show not like this :

               ^
lsl=# select version();
                                                      version                                                      
-------------------------------------------------------------------------------------------------------------------
 PostgreSQL 9.0.1 on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-46), 64-bit
(1 row)

lsl=# CREATE TABLE vv (v character(20));
INSERT INTO vv SELECT 'abc' || 'def';
SELECT v, length(v) FROM vv;
CREATE TABLE
lsl=# INSERT INTO vv SELECT 'abc' || 'def';
INSERT 0 1
lsl=# SELECT v, length(v) FROM vv;
          v           | length 
----------------------+--------
 abcdef               |      6
(1 row)


why ??   anyone  help me ? 

or  it is a  doc mistake ? 

thank you! 

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href="BLOCKQUOTE{margin-Top: 0px; margin-Bottom: 0px; margin-Left: 2em}"></HEAD>
<BODY style="MARGIN: 10px; FONT-FAMILY: verdana; FONT-SIZE: 10pt">
<DIV><A 
href="http://www.postgresql.org/docs/9.0/interactive/typeconv-query.html">http://www.postgresql.org/docs/9.0/interactive/typeconv-query.html</A> 
</DIV>
<DIV>&nbsp;</DIV>
<DIV>example shows: </DIV>
<DIV>&nbsp;</DIV>
<DIV>CREATE TABLE vv (v character(20));<BR>INSERT INTO vv SELECT 'abc' || 
'def';<BR>SELECT v, length(v) FROM 
vv;<BR><BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
v&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; | 
length<BR>----------------------+--------<BR> 
abcdef&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
|&nbsp;&nbsp;&nbsp;&nbsp; 20<BR>(1 row)</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>but&nbsp; my test show not like this :</DIV>
<DIV>&nbsp;</DIV>
<DIV>
<DIV>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;^</DIV>
<DIV>lsl=#&nbsp;select&nbsp;version();</DIV>
<DIV>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;version&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</DIV>
<DIV>-------------------------------------------------------------------------------------------------------------------</DIV>
<DIV>&nbsp;PostgreSQL&nbsp;9.0.1&nbsp;on&nbsp;x86_64-unknown-linux-gnu,&nbsp;compiled&nbsp;by&nbsp;GCC&nbsp;gcc&nbsp;(GCC)&nbsp;4.1.2&nbsp;20080704&nbsp;(Red&nbsp;Hat&nbsp;4.1.2-46),&nbsp;64-bit</DIV>
<DIV>(1&nbsp;row)</DIV></DIV>
<DIV>&nbsp;</DIV>
<DIV>
<DIV>lsl=#&nbsp;CREATE&nbsp;TABLE&nbsp;vv&nbsp;(v&nbsp;character(20));</DIV>
<DIV>INSERT&nbsp;INTO&nbsp;vv&nbsp;SELECT&nbsp;'abc'&nbsp;||&nbsp;'def';</DIV>
<DIV>SELECT&nbsp;v,&nbsp;length(v)&nbsp;FROM&nbsp;vv;</DIV>
<DIV>CREATE&nbsp;TABLE</DIV>
<DIV>lsl=#&nbsp;INSERT&nbsp;INTO&nbsp;vv&nbsp;SELECT&nbsp;'abc'&nbsp;||&nbsp;'def';</DIV>
<DIV>INSERT&nbsp;0&nbsp;1</DIV>
<DIV>lsl=#&nbsp;SELECT&nbsp;v,&nbsp;length(v)&nbsp;FROM&nbsp;vv;</DIV>
<DIV>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;v&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;length&nbsp;</DIV>
<DIV>----------------------+--------</DIV>
<DIV>&nbsp;abcdef&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;6</DIV>
<DIV>(1&nbsp;row)</DIV></DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>why ??&nbsp;&nbsp; anyone&nbsp; help me ? </DIV>
<DIV>&nbsp;</DIV>
<DIV>or&nbsp; it is a&nbsp; doc mistake ? </DIV>
<DIV>&nbsp;</DIV>
<DIV>thank you! </DIV>
<DIV>&nbsp;</DIV></BODY></HTML>

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From tgl@sss.pgh.pa.us Tue Sep  6 15:52:48 2011
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To: "lsliang" <lsliang@pconline.com.cn>
cc: "pgsql-docs" <pgsql-docs@postgresql.org>
Subject: Re: about value storage 
In-reply-to: <201109061043572514728@pconline.com.cn> 
References: <201109061043572514728@pconline.com.cn>
Comments: In-reply-to "lsliang" <lsliang@pconline.com.cn>
	message dated "Tue, 06 Sep 2011 10:43:57 +0800"
Date: Tue, 06 Sep 2011 11:52:32 -0400
Message-ID: <7708.1315324352@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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"lsliang" <lsliang@pconline.com.cn> writes:
> http://www.postgresql.org/docs/9.0/interactive/typeconv-query.html 
> example shows: 

> CREATE TABLE vv (v character(20));
> INSERT INTO vv SELECT 'abc' || 'def';
> SELECT v, length(v) FROM vv;

>           v           | length
> ----------------------+--------
>  abcdef               |     20
> (1 row)

> but  my test show not like this :

Hmm, looks like that example was overlooked when we changed the behavior
years ago:
http://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=f27976c85b1fb9002727cce65b9f9567e158f754

Given the context, we should change it to use octet_length().
Will fix, thanks.

			regards, tom lane