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Simplify references to backslash-doubling in func.sgml.

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Several places were still written as though standard_conforming_strings
didn't exist, much less be the default.  Now that it is on by default,
we can simplify the text and just insert occasional notes suggesting that
you might have to think harder if it's turned off.  Per discussion of a
suggestion from Hannes Frederic Sowa.

Back-patch to 9.1 where standard_conforming_strings was made the default.
This commit is contained in:
Tom Lane 2012-02-29 12:11:10 -05:00
parent d6a7271958
commit a5c1a1969d
1 changed files with 16 additions and 25 deletions
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41
doc/src/sgml/func.sgml
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@ -3368,8 +3368,8 @@ cast(-44 as bit(12)) <lineannotation>111111010100</lineannotation>
<para>
<function>LIKE</function> pattern matching always covers the entire
string. Therefore, to match a sequence anywhere within a string, the
pattern must start and end with a percent sign.
string. Therefore, if it's desired to match a sequence anywhere within
a string, the pattern must start and end with a percent sign.
</para>
<para>
@ -3382,17 +3382,13 @@ cast(-44 as bit(12)) <lineannotation>111111010100</lineannotation>
character itself, write two escape characters.
</para>
<para>
Note that the backslash already has a special meaning in string literals,
so to write a pattern constant that contains a backslash you must write two
backslashes in an SQL statement (assuming escape string syntax is used, see
<xref linkend="sql-syntax-strings">). Thus, writing a pattern that
actually matches a literal backslash means writing four backslashes in the
statement. You can avoid this by selecting a different escape character
with <literal>ESCAPE</literal>; then a backslash is not special to
<function>LIKE</function> anymore. (But backslash is still special to the
string literal parser, so you still need two of them to match a backslash.)
</para>
<note>
<para>
If you have <xref linkend="guc-standard-conforming-strings"> turned off,
any backslashes you write in literal string constants will need to be
doubled. See <xref linkend="sql-syntax-strings"> for more information.
</para>
</note>
<para>
It's also possible to select no escape character by writing
@ -3720,8 +3716,7 @@ substring('foobar' from 'o(.)b') <lineannotation>o</lineannotation>
inserted, and it can contain <literal>\&amp;</> to indicate that the
substring matching the entire pattern should be inserted. Write
<literal>\\</> if you need to put a literal backslash in the replacement
text. (As always, remember to double backslashes written in literal
constant strings, assuming escape string syntax is used.)
text.
The <replaceable>flags</> parameter is an optional text
string containing zero or more single-letter flags that change the
function's behavior. Flag <literal>i</> specifies case-insensitive
@ -4031,16 +4026,14 @@ SELECT foo FROM regexp_split_to_table('the quick brown fox', E'\\s*') AS foo;
</table>
<para>
An RE cannot end with <literal>\</>.
An RE cannot end with a backslash (<literal>\</>).
</para>
<note>
<para>
Remember that the backslash (<literal>\</literal>) already has a special
meaning in <productname>PostgreSQL</> string literals.
To write a pattern constant that contains a backslash,
you must write two backslashes in the statement, assuming escape
string syntax is used (see <xref linkend="sql-syntax-strings">).
If you have <xref linkend="guc-standard-conforming-strings"> turned off,
any backslashes you write in literal string constants will need to be
doubled. See <xref linkend="sql-syntax-strings"> for more information.
</para>
</note>
@ -5541,10 +5534,8 @@ SELECT SUBSTRING('XY1234Z', 'Y*?([0-9]{1,3})');
<listitem>
<para>
If you want to have a double quote in the output you must
precede it with a backslash, for example <literal>E'\\"YYYY
Month\\"'</literal>. <!-- "" font-lock sanity :-) -->
(Two backslashes are necessary because the backslash
has special meaning when using the escape string syntax.)
precede it with a backslash, for example <literal>'\"YYYY
Month\"'</literal>. <!-- "" font-lock sanity :-) -->
</para>
</listitem>