8000 Doc: improve description of trim() and related functions. · iakio/postgres@3e65fd0 · GitHub
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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
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‎doc/src/sgml/func.sgml

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@@ -1306,11 +1306,12 @@
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</entry>
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<entry><type>text</type></entry>
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<entry>
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Remove the longest string containing only the
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Remove the longest string containing only characters from
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<parameter>characters</parameter> (a space by default) from the
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start/end/both ends of the <parameter>string</parameter>
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start, end, or both ends (<literal>both</> is the default)
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of <parameter>string</parameter>
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</entry>
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<entry><literal>trim(both 'x' from 'xTomxx')</literal></entry>
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<entry><literal>trim(both 'xyz' from 'yxTomxx')</literal></entry>
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<entry><literal>Tom</literal></entry>
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</row>
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@@ -1382,7 +1383,7 @@
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in <parameter>characters</parameter> (a space by default)
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from the start and end of <parameter>string</parameter>
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</entry>
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<entry><literal>btrim('xyxtrimyyx', 'xy')</literal></entry>
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<entry><literal>btrim('xyxtrimyyx', 'xyz')</literal></entry>
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<entry><literal>trim</literal></entry>
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</row>
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@@ -1657,8 +1658,8 @@
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<parameter>characters</parameter> (a space by default) from the start of
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<parameter>string</parameter>
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</entry>
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<entry><literal>ltrim('zzzytrim', 'xyz')</literal></entry>
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<entry><literal>trim</literal></entry>
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<entry><literal>ltrim('zzzytest', 'xyz')</literal></entry>
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<entry><literal>test</literal></entry>
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</row>
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<row>
@@ -1940,8 +1941,8 @@
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<parameter>characters</parameter> (a space by default) from the end of
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<parameter>string</parameter>
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</entry>
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<entry><literal>rtrim('trimxxxx', 'x')</literal></entry>
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<entry><literal>trim</literal></entry>
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<entry><literal>rtrim('testxxzx', 'xyz')</literal></entry>
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<entry><literal>test</literal></entry>
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</row>
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<row>
@@ -2985,11 +2986,11 @@
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</entry>
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<entry><type>bytea</type></entry>
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<entry>
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Remove the longest string containing only the bytes in
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Remove the longest string containing only bytes appearing in
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<parameter>bytes</parameter> from the start
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and end of <parameter>string</parameter>
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</entry>
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<entry><literal>trim(E'\\000'::bytea from E'\\000Tom\\000'::bytea)</literal></entry>
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<entry><literal>trim(E'\\000\\001'::bytea from E'\\000Tom\\001'::bytea)</literal></entry>
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<entry><literal>Tom</literal></entry>
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</row>
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</tbody>
@@ -3028,11 +3029,11 @@
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</entry>
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<entry><type>bytea</type></entry>
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<entry>
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Remove the longest string consisting only of bytes
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in <parameter>bytes</parameter> from the start and end of
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Remove the longest string containing only bytes appearing in
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<parameter>bytes</parameter> from the start and end of
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<parameter>string</parameter>
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</entry>
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<entry><literal>btrim(E'\\000trim\\000'::bytea, E'\\000'::bytea)</literal></entry>
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<entry><literal>btrim(E'\\000trim\\001'::bytea, E'\\000\\001'::bytea)</literal></entry>
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<entry><literal>trim</literal></entry>
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</row>
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