From 213c0f2d7880f78c710127920cf4bf7017e0fa57 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 30 Nov 2016 13:34:13 -0500
Subject: [PATCH] Doc: improve description of trim() and related functions.
Per bug #14441 from Mark Pether, the documentation could be misread,
mainly because some of the examples failed to show what happens with
a multicharacter "characters to trim" string. Also, while the text
description in most of these entries was fairly clear that the
"characters" argument is a set of characters not a substring to match,
some of them used variant wording that was a bit less clear.
trim() itself suffered from both deficiencies and was thus pretty
misinterpretable.
Also fix failure to explain which of LEADING/TRAILING/BOTH is the
default.
Discussion: https://postgr.es/m/20161130011710.6539.53657@wrigleys.postgresql.org
---
doc/src/sgml/func.sgml | 33 +++++++++++++++++----------------
1 file changed, 17 insertions(+), 16 deletions(-)
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 2e64cc430c4..eca98dfd349 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1534,11 +1534,12 @@
</entry>
<entry><type>text</type></entry>
<entry>
- Remove the longest string containing only the
+ Remove the longest string containing only characters from
<parameter>characters</parameter> (a space by default) from the
- start/end/both ends of the <parameter>string</parameter>
+ start, end, or both ends (<literal>both</> is the default)
+ of <parameter>string</parameter>
</entry>
- <entry><literal>trim(both 'x' from 'xTomxx')</literal></entry>
+ <entry><literal>trim(both 'xyz' from 'yxTomxx')</literal></entry>
<entry><literal>Tom</literal></entry>
</row>
@@ -1547,14 +1548,14 @@
<literal><function>trim(<optional>leading | trailing
| both</optional> <optional>from</optional>
<parameter>string</parameter>
- <optional><parameter>, characters</parameter></optional>
+ <optional>, <parameter>characters</parameter></optional>
)</function></literal>
</entry>
<entry><type>text</type></entry>
<entry>
- Non-standard version of <function>trim()</>
+ Non-standard syntax for <function>trim()</>
</entry>
- <entry><literal>trim(both from 'xTomxx', 'x')</literal></entry>
+ <entry><literal>trim(both from 'yxTomxx', 'xyz')</literal></entry>
<entry><literal>Tom</literal></entry>
</row>
@@ -1626,7 +1627,7 @@
in <parameter>characters</parameter> (a space by default)
from the start and end of <parameter>string</parameter>
</entry>
- <entry><literal>btrim('xyxtrimyyx', 'xy')</literal></entry>
+ <entry><literal>btrim('xyxtrimyyx', 'xyz')</literal></entry>
<entry><literal>trim</literal></entry>
</row>
@@ -1895,8 +1896,8 @@
<parameter>characters</parameter> (a space by default) from the start of
<parameter>string</parameter>
</entry>
- <entry><literal>ltrim('zzzytrim', 'xyz')</literal></entry>
- <entry><literal>trim</literal></entry>
+ <entry><literal>ltrim('zzzytest', 'xyz')</literal></entry>
+ <entry><literal>test</literal></entry>
</row>
<row>
@@ -2218,8 +2219,8 @@
<parameter>characters</parameter> (a space by default) from the end of
<parameter>string</parameter>
</entry>
- <entry><literal>rtrim('trimxxxx', 'x')</literal></entry>
- <entry><literal>trim</literal></entry>
+ <entry><literal>rtrim('testxxzx', 'xyz')</literal></entry>
+ <entry><literal>test</literal></entry>
</row>
<row>
@@ -3484,11 +3485,11 @@ SELECT format('Testing %3$s, %2$s, %s', 'one', 'two', 'three');
</entry>
<entry><type>bytea</type></entry>
<entry>
- Remove the longest string containing only the bytes in
+ Remove the longest string containing only bytes appearing in
<parameter>bytes</parameter> from the start
and end of <parameter>string</parameter>
</entry>
- <entry><literal>trim(E'\\000'::bytea from E'\\000Tom\\000'::bytea)</literal></entry>
+ <entry><literal>trim(E'\\000\\001'::bytea from E'\\000Tom\\001'::bytea)</literal></entry>
<entry><literal>Tom</literal></entry>
</row>
</tbody>
@@ -3527,11 +3528,11 @@ SELECT format('Testing %3$s, %2$s, %s', 'one', 'two', 'three');
</entry>
<entry><type>bytea</type></entry>
<entry>
- Remove the longest string consisting only of bytes
- in <parameter>bytes</parameter> from the start and end of
+ Remove the longest string containing only bytes appearing in
+ <parameter>bytes</parameter> from the start and end of
<parameter>string</parameter>
</entry>
- <entry><literal>btrim(E'\\000trim\\000'::bytea, E'\\000'::bytea)</literal></entry>
+ <entry><literal>btrim(E'\\000trim\\001'::bytea, E'\\000\\001'::bytea)</literal></entry>
<entry><literal>trim</literal></entry>
</row>
--
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