Split func.sgml into more manageable pieces

func.sgml has grown over the years to the point where it is very
difficult to manage. This commit splits out each sect1 piece into its
own file, which is then included in the main file, so that the built
documentation should be identical to the pre-split documentation. All
these new files are placed in a new "func" subdirectory, and the
previous func.sgml is removed.

Done using scripts developed by:

Author: jian he <jian.universality@gmail.com>

Discussion: https://postgr.es/m/CACJufxFgAh1--EMwOjMuANe=VTmjkNaZjH+AzSe04-8ZCGiESA@mail.gmail.com

1 files changed, 1818 insertions, 0 deletions

diff --git a/doc/src/sgml/func/func-string.sgml b/doc/src/sgml/func/func-string.sgml
new file mode 100644
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+  <sect1 id="functions-string">
+   <title>String Functions and Operators</title>
+
+   <para>
+    This section describes functions and operators for examining and
+    manipulating string values.  Strings in this context include values
+    of the types <type>character</type>, <type>character varying</type>,
+    and <type>text</type>.  Except where noted, these functions and operators
+    are declared to accept and return type <type>text</type>.  They will
+    interchangeably accept <type>character varying</type> arguments.
+    Values of type <type>character</type> will be converted
+    to <type>text</type> before the function or operator is applied, resulting
+    in stripping any trailing spaces in the <type>character</type> value.
+   </para>
+
+   <para>
+    <acronym>SQL</acronym> defines some string functions that use
+    key words, rather than commas, to separate
+    arguments.  Details are in
+    <xref linkend="functions-string-sql"/>.
+    <productname>PostgreSQL</productname> also provides versions of these functions
+    that use the regular function invocation syntax
+    (see <xref linkend="functions-string-other"/>).
+   </para>
+
+   <note>
+    <para>
+     The string concatenation operator (<literal>||</literal>) will accept
+     non-string input, so long as at least one input is of string type, as shown
+     in <xref linkend="functions-string-sql"/>.  For other cases, inserting an
+     explicit coercion to <type>text</type> can be used to have non-string input
+     accepted.
+    </para>
+   </note>
+
+   <table id="functions-string-sql">
+    <title><acronym>SQL</acronym> String Functions and Operators</title>
+    <tgroup cols="1">
+     <thead>
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        Function/Operator
+       </para>
+       <para>
+        Description
+       </para>
+       <para>
+        Example(s)
+       </para></entry>
+      </row>
+     </thead>
+
+     <tbody>
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>character string</primary>
+         <secondary>concatenation</secondary>
+        </indexterm>
+        <type>text</type> <literal>||</literal> <type>text</type>
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Concatenates the two strings.
+       </para>
+       <para>
+        <literal>'Post' || 'greSQL'</literal>
+        <returnvalue>PostgreSQL</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <type>text</type> <literal>||</literal> <type>anynonarray</type>
+        <returnvalue>text</returnvalue>
+       </para>
+       <para role="func_signature">
+        <type>anynonarray</type> <literal>||</literal> <type>text</type>
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the non-string input to text, then concatenates the two
+        strings.  (The non-string input cannot be of an array type, because
+        that would create ambiguity with the array <literal>||</literal>
+        operators.  If you want to concatenate an array's text equivalent,
+        cast it to <type>text</type> explicitly.)
+       </para>
+       <para>
+        <literal>'Value: ' || 42</literal>
+        <returnvalue>Value: 42</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>btrim</primary>
+        </indexterm>
+        <function>btrim</function> ( <parameter>string</parameter> <type>text</type>
+        <optional>, <parameter>characters</parameter> <type>text</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Removes the longest string containing only characters
+        in <parameter>characters</parameter> (a space by default)
+        from the start and end of <parameter>string</parameter>.
+       </para>
+       <para>
+        <literal>btrim('xyxtrimyyx', 'xyz')</literal>
+        <returnvalue>trim</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>normalized</primary>
+        </indexterm>
+        <indexterm>
+         <primary>Unicode normalization</primary>
+        </indexterm>
+         <type>text</type> <literal>IS</literal> <optional><literal>NOT</literal></optional> <optional><parameter>form</parameter></optional> <literal>NORMALIZED</literal>
+        <returnvalue>boolean</returnvalue>
+       </para>
+       <para>
+        Checks whether the string is in the specified Unicode normalization
+        form.  The optional <parameter>form</parameter> key word specifies the
+        form: <literal>NFC</literal> (the default), <literal>NFD</literal>,
+        <literal>NFKC</literal>, or <literal>NFKD</literal>.  This expression can
+        only be used when the server encoding is <literal>UTF8</literal>.  Note
+        that checking for normalization using this expression is often faster
+        than normalizing possibly already normalized strings.
+       </para>
+       <para>
+        <literal>U&amp;'\0061\0308bc' IS NFD NORMALIZED</literal>
+        <returnvalue>t</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>bit_length</primary>
+        </indexterm>
+        <function>bit_length</function> ( <type>text</type> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns number of bits in the string (8
+        times the <function>octet_length</function>).
+       </para>
+       <para>
+        <literal>bit_length('jose')</literal>
+        <returnvalue>32</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>char_length</primary>
+        </indexterm>
+        <indexterm>
+         <primary>character string</primary>
+         <secondary>length</secondary>
+        </indexterm>
+        <indexterm>
+         <primary>length</primary>
+         <secondary sortas="character string">of a character string</secondary>
+         <see>character string, length</see>
+        </indexterm>
+        <function>char_length</function> ( <type>text</type> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para role="func_signature">
+        <indexterm>
+         <primary>character_length</primary>
+        </indexterm>
+        <function>character_length</function> ( <type>text</type> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns number of characters in the string.
+       </para>
+       <para>
+        <literal>char_length('jos&eacute;')</literal>
+        <returnvalue>4</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm id="function-lower">
+         <primary>lower</primary>
+        </indexterm>
+        <function>lower</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the string to all lower case, according to the rules of the
+        database's locale.
+       </para>
+       <para>
+        <literal>lower('TOM')</literal>
+        <returnvalue>tom</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>lpad</primary>
+        </indexterm>
+        <function>lpad</function> ( <parameter>string</parameter> <type>text</type>,
+        <parameter>length</parameter> <type>integer</type>
+        <optional>, <parameter>fill</parameter> <type>text</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Extends the <parameter>string</parameter> to length
+        <parameter>length</parameter> by prepending the characters
+        <parameter>fill</parameter> (a space by default).  If the
+        <parameter>string</parameter> is already longer than
+        <parameter>length</parameter> then it is truncated (on the right).
+       </para>
+       <para>
+        <literal>lpad('hi', 5, 'xy')</literal>
+        <returnvalue>xyxhi</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>ltrim</primary>
+        </indexterm>
+        <function>ltrim</function> ( <parameter>string</parameter> <type>text</type>
+        <optional>, <parameter>characters</parameter> <type>text</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Removes the longest string containing only characters in
+        <parameter>characters</parameter> (a space by default) from the start of
+        <parameter>string</parameter>.
+       </para>
+       <para>
+        <literal>ltrim('zzzytest', 'xyz')</literal>
+        <returnvalue>test</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm id="function-normalize">
+         <primary>normalize</primary>
+        </indexterm>
+        <indexterm>
+         <primary>Unicode normalization</primary>
+        </indexterm>
+        <function>normalize</function> ( <type>text</type>
+        <optional>, <parameter>form</parameter> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the string to the specified Unicode
+        normalization form.  The optional <parameter>form</parameter> key word
+        specifies the form: <literal>NFC</literal> (the default),
+        <literal>NFD</literal>, <literal>NFKC</literal>, or
+        <literal>NFKD</literal>.  This function can only be used when the
+        server encoding is <literal>UTF8</literal>.
+       </para>
+       <para>
+        <literal>normalize(U&amp;'\0061\0308bc', NFC)</literal>
+        <returnvalue>U&amp;'\00E4bc'</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>octet_length</primary>
+        </indexterm>
+        <function>octet_length</function> ( <type>text</type> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns number of bytes in the string.
+       </para>
+       <para>
+        <literal>octet_length('jos&eacute;')</literal>
+        <returnvalue>5</returnvalue> (if server encoding is UTF8)
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>octet_length</primary>
+        </indexterm>
+        <function>octet_length</function> ( <type>character</type> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns number of bytes in the string.  Since this version of the
+        function accepts type <type>character</type> directly, it will not
+        strip trailing spaces.
+       </para>
+       <para>
+        <literal>octet_length('abc '::character(4))</literal>
+        <returnvalue>4</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>overlay</primary>
+        </indexterm>
+        <function>overlay</function> ( <parameter>string</parameter> <type>text</type> <literal>PLACING</literal> <parameter>newsubstring</parameter> <type>text</type> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Replaces the substring of <parameter>string</parameter> that starts at
+        the <parameter>start</parameter>'th character and extends
+        for <parameter>count</parameter> characters
+        with <parameter>newsubstring</parameter>.
+        If <parameter>count</parameter> is omitted, it defaults to the length
+        of <parameter>newsubstring</parameter>.
+       </para>
+       <para>
+        <literal>overlay('Txxxxas' placing 'hom' from 2 for 4)</literal>
+        <returnvalue>Thomas</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>position</primary>
+        </indexterm>
+        <function>position</function> ( <parameter>substring</parameter> <type>text</type> <literal>IN</literal> <parameter>string</parameter> <type>text</type> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns first starting index of the specified
+        <parameter>substring</parameter> within
+        <parameter>string</parameter>, or zero if it's not present.
+       </para>
+       <para>
+        <literal>position('om' in 'Thomas')</literal>
+        <returnvalue>3</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>rpad</primary>
+        </indexterm>
+        <function>rpad</function> ( <parameter>string</parameter> <type>text</type>,
+        <parameter>length</parameter> <type>integer</type>
+        <optional>, <parameter>fill</parameter> <type>text</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Extends the <parameter>string</parameter> to length
+        <parameter>length</parameter> by appending the characters
+        <parameter>fill</parameter> (a space by default).  If the
+        <parameter>string</parameter> is already longer than
+        <parameter>length</parameter> then it is truncated.
+       </para>
+       <para>
+        <literal>rpad('hi', 5, 'xy')</literal>
+        <returnvalue>hixyx</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>rtrim</primary>
+        </indexterm>
+        <function>rtrim</function> ( <parameter>string</parameter> <type>text</type>
+         <optional>, <parameter>characters</parameter> <type>text</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Removes the longest string containing only characters in
+        <parameter>characters</parameter> (a space by default) from the end of
+        <parameter>string</parameter>.
+       </para>
+       <para>
+        <literal>rtrim('testxxzx', 'xyz')</literal>
+        <returnvalue>test</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>substring</primary>
+        </indexterm>
+        <function>substring</function> ( <parameter>string</parameter> <type>text</type> <optional> <literal>FROM</literal> <parameter>start</parameter> <type>integer</type> </optional> <optional> <literal>FOR</literal> <parameter>count</parameter> <type>integer</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Extracts the substring of <parameter>string</parameter> starting at
+        the <parameter>start</parameter>'th character if that is specified,
+        and stopping after <parameter>count</parameter> characters if that is
+        specified.  Provide at least one of <parameter>start</parameter>
+        and <parameter>count</parameter>.
+       </para>
+       <para>
+        <literal>substring('Thomas' from 2 for 3)</literal>
+        <returnvalue>hom</returnvalue>
+       </para>
+       <para>
+        <literal>substring('Thomas' from 3)</literal>
+        <returnvalue>omas</returnvalue>
+       </para>
+       <para>
+        <literal>substring('Thomas' for 2)</literal>
+        <returnvalue>Th</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <function>substring</function> ( <parameter>string</parameter> <type>text</type> <literal>FROM</literal> <parameter>pattern</parameter> <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Extracts the first substring matching POSIX regular expression; see
+        <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>substring('Thomas' from '...$')</literal>
+        <returnvalue>mas</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <function>substring</function> ( <parameter>string</parameter> <type>text</type> <literal>SIMILAR</literal> <parameter>pattern</parameter> <type>text</type> <literal>ESCAPE</literal> <parameter>escape</parameter> <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para role="func_signature">
+        <function>substring</function> ( <parameter>string</parameter> <type>text</type> <literal>FROM</literal> <parameter>pattern</parameter> <type>text</type> <literal>FOR</literal> <parameter>escape</parameter> <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Extracts the first substring matching <acronym>SQL</acronym> regular expression;
+        see <xref linkend="functions-similarto-regexp"/>.  The first form has
+        been specified since SQL:2003; the second form was only in SQL:1999
+        and should be considered obsolete.
+       </para>
+       <para>
+        <literal>substring('Thomas' similar '%#"o_a#"_' escape '#')</literal>
+        <returnvalue>oma</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>trim</primary>
+        </indexterm>
+        <function>trim</function> ( <optional> <literal>LEADING</literal> | <literal>TRAILING</literal> | <literal>BOTH</literal> </optional>
+        <optional> <parameter>characters</parameter> <type>text</type> </optional> <literal>FROM</literal>
+        <parameter>string</parameter> <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Removes the longest string containing only characters in
+        <parameter>characters</parameter> (a space by default) from the
+        start, end, or both ends (<literal>BOTH</literal> is the default)
+        of <parameter>string</parameter>.
+       </para>
+       <para>
+        <literal>trim(both 'xyz' from 'yxTomxx')</literal>
+        <returnvalue>Tom</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <function>trim</function> ( <optional> <literal>LEADING</literal> | <literal>TRAILING</literal> | <literal>BOTH</literal> </optional> <optional> <literal>FROM</literal> </optional>
+        <parameter>string</parameter> <type>text</type> <optional>,
+        <parameter>characters</parameter> <type>text</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        This is a non-standard syntax for <function>trim()</function>.
+       </para>
+       <para>
+        <literal>trim(both from 'yxTomxx', 'xyz')</literal>
+        <returnvalue>Tom</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>unicode_assigned</primary>
+        </indexterm>
+        <function>unicode_assigned</function> ( <type>text</type> )
+        <returnvalue>boolean</returnvalue>
+       </para>
+       <para>
+        Returns <literal>true</literal> if all characters in the string are
+        assigned Unicode codepoints; <literal>false</literal> otherwise. This
+        function can only be used when the server encoding is
+        <literal>UTF8</literal>.
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>upper</primary>
+        </indexterm>
+        <function>upper</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the string to all upper case, according to the rules of the
+        database's locale.
+       </para>
+       <para>
+        <literal>upper('tom')</literal>
+        <returnvalue>TOM</returnvalue>
+       </para></entry>
+      </row>
+     </tbody>
+    </tgroup>
+   </table>
+
+   <para>
+    Additional string manipulation functions and operators are available
+    and are listed in <xref linkend="functions-string-other"/>.  (Some of
+    these are used internally to implement
+    the <acronym>SQL</acronym>-standard string functions listed in
+    <xref linkend="functions-string-sql"/>.)
+    There are also pattern-matching operators, which are described in
+    <xref linkend="functions-matching"/>, and operators for full-text
+    search, which are described in <xref linkend="textsearch"/>.
+   </para>
+
+   <table id="functions-string-other">
+    <title>Other String Functions and Operators</title>
+    <tgroup cols="1">
+     <thead>
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        Function/Operator
+       </para>
+       <para>
+        Description
+       </para>
+       <para>
+        Example(s)
+       </para></entry>
+      </row>
+     </thead>
+
+     <tbody>
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>character string</primary>
+         <secondary>prefix test</secondary>
+        </indexterm>
+        <type>text</type> <literal>^@</literal> <type>text</type>
+        <returnvalue>boolean</returnvalue>
+       </para>
+       <para>
+        Returns true if the first string starts with the second string
+        (equivalent to the <function>starts_with()</function> function).
+       </para>
+       <para>
+        <literal>'alphabet' ^@ 'alph'</literal>
+        <returnvalue>t</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>ascii</primary>
+        </indexterm>
+        <function>ascii</function> ( <type>text</type> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns the numeric code of the first character of the argument.
+        In <acronym>UTF8</acronym> encoding, returns the Unicode code point
+        of the character.  In other multibyte encodings, the argument must
+        be an <acronym>ASCII</acronym> character.
+       </para>
+       <para>
+        <literal>ascii('x')</literal>
+        <returnvalue>120</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>chr</primary>
+        </indexterm>
+        <function>chr</function> ( <type>integer</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns the character with the given code. In <acronym>UTF8</acronym>
+        encoding the argument is treated as a Unicode code point. In other
+        multibyte encodings the argument must designate
+        an <acronym>ASCII</acronym> character.  <literal>chr(0)</literal> is
+        disallowed because text data types cannot store that character.
+      </para>
+      <para>
+        <literal>chr(65)</literal>
+        <returnvalue>A</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>concat</primary>
+        </indexterm>
+        <function>concat</function> ( <parameter>val1</parameter> <type>"any"</type>
+         <optional>, <parameter>val2</parameter> <type>"any"</type> <optional>, ...</optional> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Concatenates the text representations of all the arguments.
+        NULL arguments are ignored.
+       </para>
+       <para>
+        <literal>concat('abcde', 2, NULL, 22)</literal>
+        <returnvalue>abcde222</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>concat_ws</primary>
+        </indexterm>
+        <function>concat_ws</function> ( <parameter>sep</parameter> <type>text</type>,
+        <parameter>val1</parameter> <type>"any"</type>
+        <optional>, <parameter>val2</parameter> <type>"any"</type> <optional>, ...</optional> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Concatenates all but the first argument, with separators. The first
+        argument is used as the separator string, and should not be NULL.
+        Other NULL arguments are ignored.
+       </para>
+       <para>
+        <literal>concat_ws(',', 'abcde', 2, NULL, 22)</literal>
+        <returnvalue>abcde,2,22</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>format</primary>
+        </indexterm>
+        <function>format</function> ( <parameter>formatstr</parameter> <type>text</type>
+        <optional>, <parameter>formatarg</parameter> <type>"any"</type> <optional>, ...</optional> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+         Formats arguments according to a format string;
+         see <xref linkend="functions-string-format"/>.
+         This function is similar to the C function <function>sprintf</function>.
+       </para>
+       <para>
+        <literal>format('Hello %s, %1$s', 'World')</literal>
+        <returnvalue>Hello World, World</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>initcap</primary>
+        </indexterm>
+        <function>initcap</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the first letter of each word to upper case and the
+        rest to lower case. When using the <literal>libc</literal> locale
+        provider, words are sequences of alphanumeric characters separated
+        by non-alphanumeric characters; when using the ICU locale provider,
+        words are separated according to
+        <ulink url="https://www.unicode.org/reports/tr29/#Word_Boundaries">Unicode Standard Annex #29</ulink>.
+       </para>
+       <para>
+        <literal>initcap('hi THOMAS')</literal>
+        <returnvalue>Hi Thomas</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>casefold</primary>
+        </indexterm>
+        <function>casefold</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Performs case folding of the input string according to the collation.
+        Case folding is similar to case conversion, but the purpose of case
+        folding is to facilitate case-insensitive matching of strings,
+        whereas the purpose of case conversion is to convert to a particular
+        cased form.  This function can only be used when the server encoding
+        is <literal>UTF8</literal>.
+       </para>
+       <para>
+        Ordinarily, case folding simply converts to lowercase, but there may
+        be exceptions depending on the collation.  For instance, some
+        characters have more than two lowercase variants, or fold to uppercase.
+       </para>
+       <para>
+        Case folding may change the length of the string.  For instance, in
+        the <literal>PG_UNICODE_FAST</literal> collation, <literal>ß</literal>
+        (U+00DF) folds to <literal>ss</literal>.
+       </para>
+       <para>
+        <function>casefold</function> can be used for Unicode Default Caseless
+        Matching.  It does not always preserve the normalized form of the
+        input string (see <xref linkend="function-normalize"/>).
+       </para>
+       <para>
+        The <literal>libc</literal> provider doesn't support case folding, so
+        <function>casefold</function> is identical to <xref
+        linkend="function-lower"/>.
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>left</primary>
+        </indexterm>
+        <function>left</function> ( <parameter>string</parameter> <type>text</type>,
+        <parameter>n</parameter> <type>integer</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns first <parameter>n</parameter> characters in the
+        string, or when <parameter>n</parameter> is negative, returns
+        all but last |<parameter>n</parameter>| characters.
+       </para>
+       <para>
+        <literal>left('abcde', 2)</literal>
+        <returnvalue>ab</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>length</primary>
+        </indexterm>
+        <function>length</function> ( <type>text</type> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns the number of characters in the string.
+       </para>
+       <para>
+        <literal>length('jose')</literal>
+        <returnvalue>4</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>md5</primary>
+        </indexterm>
+        <function>md5</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Computes the MD5 <link linkend="functions-hash-note">hash</link> of
+        the argument, with the result written in hexadecimal.
+       </para>
+       <para>
+        <literal>md5('abc')</literal>
+        <returnvalue>900150983cd24fb0&zwsp;d6963f7d28e17f72</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>parse_ident</primary>
+        </indexterm>
+        <function>parse_ident</function> ( <parameter>qualified_identifier</parameter> <type>text</type>
+        <optional>, <parameter>strict_mode</parameter> <type>boolean</type> <literal>DEFAULT</literal> <literal>true</literal> </optional> )
+        <returnvalue>text[]</returnvalue>
+       </para>
+       <para>
+        Splits <parameter>qualified_identifier</parameter> into an array of
+        identifiers, removing any quoting of individual identifiers.  By
+        default, extra characters after the last identifier are considered an
+        error; but if the second parameter is <literal>false</literal>, then such
+        extra characters are ignored. (This behavior is useful for parsing
+        names for objects like functions.) Note that this function does not
+        truncate over-length identifiers. If you want truncation you can cast
+        the result to <type>name[]</type>.
+       </para>
+       <para>
+        <literal>parse_ident('"SomeSchema".someTable')</literal>
+        <returnvalue>{SomeSchema,sometable}</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_client_encoding</primary>
+        </indexterm>
+        <function>pg_client_encoding</function> ( )
+        <returnvalue>name</returnvalue>
+       </para>
+       <para>
+        Returns current client encoding name.
+       </para>
+       <para>
+        <literal>pg_client_encoding()</literal>
+        <returnvalue>UTF8</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>quote_ident</primary>
+        </indexterm>
+        <function>quote_ident</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns the given string suitably quoted to be used as an identifier
+        in an <acronym>SQL</acronym> statement string.
+        Quotes are added only if necessary (i.e., if the string contains
+        non-identifier characters or would be case-folded).
+        Embedded quotes are properly doubled.
+        See also <xref linkend="plpgsql-quote-literal-example"/>.
+       </para>
+       <para>
+        <literal>quote_ident('Foo bar')</literal>
+        <returnvalue>"Foo bar"</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>quote_literal</primary>
+        </indexterm>
+        <function>quote_literal</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns the given string suitably quoted to be used as a string literal
+        in an <acronym>SQL</acronym> statement string.
+        Embedded single-quotes and backslashes are properly doubled.
+        Note that <function>quote_literal</function> returns null on null
+        input; if the argument might be null,
+        <function>quote_nullable</function> is often more suitable.
+        See also <xref linkend="plpgsql-quote-literal-example"/>.
+       </para>
+       <para>
+        <literal>quote_literal(E'O\'Reilly')</literal>
+        <returnvalue>'O''Reilly'</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <function>quote_literal</function> ( <type>anyelement</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the given value to text and then quotes it as a literal.
+        Embedded single-quotes and backslashes are properly doubled.
+       </para>
+       <para>
+        <literal>quote_literal(42.5)</literal>
+        <returnvalue>'42.5'</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>quote_nullable</primary>
+        </indexterm>
+        <function>quote_nullable</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns the given string suitably quoted to be used as a string literal
+        in an <acronym>SQL</acronym> statement string; or, if the argument
+        is null, returns <literal>NULL</literal>.
+        Embedded single-quotes and backslashes are properly doubled.
+        See also <xref linkend="plpgsql-quote-literal-example"/>.
+       </para>
+       <para>
+        <literal>quote_nullable(NULL)</literal>
+        <returnvalue>NULL</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <function>quote_nullable</function> ( <type>anyelement</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the given value to text and then quotes it as a literal;
+        or, if the argument is null, returns <literal>NULL</literal>.
+        Embedded single-quotes and backslashes are properly doubled.
+       </para>
+       <para>
+        <literal>quote_nullable(42.5)</literal>
+        <returnvalue>'42.5'</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>regexp_count</primary>
+        </indexterm>
+        <function>regexp_count</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>
+         <optional>, <parameter>start</parameter> <type>integer</type>
+         <optional>, <parameter>flags</parameter> <type>text</type> </optional> </optional> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns the number of times the POSIX regular
+        expression <parameter>pattern</parameter> matches in
+        the <parameter>string</parameter>; see
+        <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_count('123456789012', '\d\d\d', 2)</literal>
+        <returnvalue>3</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>regexp_instr</primary>
+        </indexterm>
+        <function>regexp_instr</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>
+         <optional>, <parameter>start</parameter> <type>integer</type>
+         <optional>, <parameter>N</parameter> <type>integer</type>
+         <optional>, <parameter>endoption</parameter> <type>integer</type>
+         <optional>, <parameter>flags</parameter> <type>text</type>
+         <optional>, <parameter>subexpr</parameter> <type>integer</type> </optional> </optional> </optional> </optional> </optional> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns the position within <parameter>string</parameter> where
+        the <parameter>N</parameter>'th match of the POSIX regular
+        expression <parameter>pattern</parameter> occurs, or zero if there is
+        no such match; see <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_instr('ABCDEF', 'c(.)(..)', 1, 1, 0, 'i')</literal>
+        <returnvalue>3</returnvalue>
+       </para>
+       <para>
+        <literal>regexp_instr('ABCDEF', 'c(.)(..)', 1, 1, 0, 'i', 2)</literal>
+        <returnvalue>5</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>regexp_like</primary>
+        </indexterm>
+        <function>regexp_like</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>
+         <optional>, <parameter>flags</parameter> <type>text</type> </optional> )
+        <returnvalue>boolean</returnvalue>
+       </para>
+       <para>
+        Checks whether a match of the POSIX regular
+        expression <parameter>pattern</parameter> occurs
+        within <parameter>string</parameter>; see
+        <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_like('Hello World', 'world$', 'i')</literal>
+        <returnvalue>t</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>regexp_match</primary>
+        </indexterm>
+        <function>regexp_match</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> <optional>, <parameter>flags</parameter> <type>text</type> </optional> )
+        <returnvalue>text[]</returnvalue>
+       </para>
+       <para>
+        Returns substrings within the first match of the POSIX regular
+        expression <parameter>pattern</parameter> to
+        the <parameter>string</parameter>; see
+        <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_match('foobarbequebaz', '(bar)(beque)')</literal>
+        <returnvalue>{bar,beque}</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>regexp_matches</primary>
+        </indexterm>
+        <function>regexp_matches</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> <optional>, <parameter>flags</parameter> <type>text</type> </optional> )
+        <returnvalue>setof text[]</returnvalue>
+       </para>
+       <para>
+        Returns substrings within the first match of the POSIX regular
+        expression <parameter>pattern</parameter> to
+        the <parameter>string</parameter>, or substrings within all
+        such matches if the <literal>g</literal> flag is used;
+        see <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_matches('foobarbequebaz', 'ba.', 'g')</literal>
+        <returnvalue></returnvalue>
+<programlisting>
+ {bar}
+ {baz}
+</programlisting>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>regexp_replace</primary>
+        </indexterm>
+        <function>regexp_replace</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>, <parameter>replacement</parameter> <type>text</type>
+         <optional>, <parameter>flags</parameter> <type>text</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Replaces the substring that is the first match to the POSIX
+        regular expression <parameter>pattern</parameter>, or all such
+        matches if the <literal>g</literal> flag is used; see
+        <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_replace('Thomas', '.[mN]a.', 'M')</literal>
+        <returnvalue>ThM</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <function>regexp_replace</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>, <parameter>replacement</parameter> <type>text</type>,
+         <parameter>start</parameter> <type>integer</type>
+         <optional>, <parameter>N</parameter> <type>integer</type>
+         <optional>, <parameter>flags</parameter> <type>text</type> </optional> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Replaces the substring that is the <parameter>N</parameter>'th
+        match to the POSIX regular expression <parameter>pattern</parameter>,
+        or all such matches if <parameter>N</parameter> is zero, with the
+        search beginning at the <parameter>start</parameter>'th character
+        of <parameter>string</parameter>.  If <parameter>N</parameter> is
+        omitted, it defaults to 1.  See
+        <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_replace('Thomas', '.', 'X', 3, 2)</literal>
+        <returnvalue>ThoXas</returnvalue>
+       </para>
+       <para>
+        <literal>regexp_replace(string=>'hello world', pattern=>'l', replacement=>'XX', start=>1, "N"=>2)</literal>
+        <returnvalue>helXXo world</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>regexp_split_to_array</primary>
+        </indexterm>
+        <function>regexp_split_to_array</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> <optional>, <parameter>flags</parameter> <type>text</type> </optional> )
+        <returnvalue>text[]</returnvalue>
+       </para>
+       <para>
+        Splits <parameter>string</parameter> using a POSIX regular
+        expression as the delimiter, producing an array of results; see
+        <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_split_to_array('hello world', '\s+')</literal>
+        <returnvalue>{hello,world}</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>regexp_split_to_table</primary>
+        </indexterm>
+        <function>regexp_split_to_table</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type> <optional>, <parameter>flags</parameter> <type>text</type> </optional> )
+        <returnvalue>setof text</returnvalue>
+       </para>
+       <para>
+        Splits <parameter>string</parameter> using a POSIX regular
+        expression as the delimiter, producing a set of results; see
+        <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_split_to_table('hello world', '\s+')</literal>
+        <returnvalue></returnvalue>
+<programlisting>
+ hello
+ world
+</programlisting>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>regexp_substr</primary>
+        </indexterm>
+        <function>regexp_substr</function> ( <parameter>string</parameter> <type>text</type>, <parameter>pattern</parameter> <type>text</type>
+         <optional>, <parameter>start</parameter> <type>integer</type>
+         <optional>, <parameter>N</parameter> <type>integer</type>
+         <optional>, <parameter>flags</parameter> <type>text</type>
+         <optional>, <parameter>subexpr</parameter> <type>integer</type> </optional> </optional> </optional> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns the substring within <parameter>string</parameter> that
+        matches the <parameter>N</parameter>'th occurrence of the POSIX
+        regular expression <parameter>pattern</parameter>,
+        or <literal>NULL</literal> if there is no such match; see
+        <xref linkend="functions-posix-regexp"/>.
+       </para>
+       <para>
+        <literal>regexp_substr('ABCDEF', 'c(.)(..)', 1, 1, 'i')</literal>
+        <returnvalue>CDEF</returnvalue>
+       </para>
+       <para>
+        <literal>regexp_substr('ABCDEF', 'c(.)(..)', 1, 1, 'i', 2)</literal>
+        <returnvalue>EF</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>repeat</primary>
+        </indexterm>
+        <function>repeat</function> ( <parameter>string</parameter> <type>text</type>, <parameter>number</parameter> <type>integer</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Repeats <parameter>string</parameter> the specified
+        <parameter>number</parameter> of times.
+       </para>
+       <para>
+        <literal>repeat('Pg', 4)</literal>
+        <returnvalue>PgPgPgPg</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>replace</primary>
+        </indexterm>
+        <function>replace</function> ( <parameter>string</parameter> <type>text</type>,
+        <parameter>from</parameter> <type>text</type>,
+        <parameter>to</parameter> <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Replaces all occurrences in <parameter>string</parameter> of
+        substring <parameter>from</parameter> with
+        substring <parameter>to</parameter>.
+       </para>
+       <para>
+        <literal>replace('abcdefabcdef', 'cd', 'XX')</literal>
+        <returnvalue>abXXefabXXef</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>reverse</primary>
+        </indexterm>
+        <function>reverse</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Reverses the order of the characters in the string.
+       </para>
+       <para>
+        <literal>reverse('abcde')</literal>
+        <returnvalue>edcba</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>right</primary>
+        </indexterm>
+        <function>right</function> ( <parameter>string</parameter> <type>text</type>,
+         <parameter>n</parameter> <type>integer</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Returns last <parameter>n</parameter> characters in the string,
+        or when <parameter>n</parameter> is negative, returns all but
+        first |<parameter>n</parameter>| characters.
+       </para>
+       <para>
+        <literal>right('abcde', 2)</literal>
+        <returnvalue>de</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>split_part</primary>
+        </indexterm>
+        <function>split_part</function> ( <parameter>string</parameter> <type>text</type>,
+        <parameter>delimiter</parameter> <type>text</type>,
+        <parameter>n</parameter> <type>integer</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Splits <parameter>string</parameter> at occurrences
+        of <parameter>delimiter</parameter> and returns
+        the <parameter>n</parameter>'th field (counting from one),
+        or when <parameter>n</parameter> is negative, returns
+        the |<parameter>n</parameter>|'th-from-last field.
+       </para>
+       <para>
+        <literal>split_part('abc~@~def~@~ghi', '~@~', 2)</literal>
+        <returnvalue>def</returnvalue>
+       </para>
+       <para>
+        <literal>split_part('abc,def,ghi,jkl', ',', -2)</literal>
+        <returnvalue>ghi</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>starts_with</primary>
+        </indexterm>
+        <function>starts_with</function> ( <parameter>string</parameter> <type>text</type>, <parameter>prefix</parameter> <type>text</type> )
+        <returnvalue>boolean</returnvalue>
+       </para>
+       <para>
+        Returns true if <parameter>string</parameter> starts
+        with <parameter>prefix</parameter>.
+       </para>
+       <para>
+        <literal>starts_with('alphabet', 'alph')</literal>
+        <returnvalue>t</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm id="function-string-to-array">
+         <primary>string_to_array</primary>
+        </indexterm>
+        <function>string_to_array</function> ( <parameter>string</parameter> <type>text</type>, <parameter>delimiter</parameter> <type>text</type> <optional>, <parameter>null_string</parameter> <type>text</type> </optional> )
+        <returnvalue>text[]</returnvalue>
+       </para>
+       <para>
+        Splits the <parameter>string</parameter> at occurrences
+        of <parameter>delimiter</parameter> and forms the resulting fields
+        into a <type>text</type> array.
+        If <parameter>delimiter</parameter> is <literal>NULL</literal>,
+        each character in the <parameter>string</parameter> will become a
+        separate element in the array.
+        If <parameter>delimiter</parameter> is an empty string, then
+        the <parameter>string</parameter> is treated as a single field.
+        If <parameter>null_string</parameter> is supplied and is
+        not <literal>NULL</literal>, fields matching that string are
+        replaced by <literal>NULL</literal>.
+        See also <link linkend="function-array-to-string"><function>array_to_string</function></link>.
+       </para>
+       <para>
+        <literal>string_to_array('xx~~yy~~zz', '~~', 'yy')</literal>
+        <returnvalue>{xx,NULL,zz}</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>string_to_table</primary>
+        </indexterm>
+        <function>string_to_table</function> ( <parameter>string</parameter> <type>text</type>, <parameter>delimiter</parameter> <type>text</type> <optional>, <parameter>null_string</parameter> <type>text</type> </optional> )
+        <returnvalue>setof text</returnvalue>
+       </para>
+       <para>
+        Splits the <parameter>string</parameter> at occurrences
+        of <parameter>delimiter</parameter> and returns the resulting fields
+        as a set of <type>text</type> rows.
+        If <parameter>delimiter</parameter> is <literal>NULL</literal>,
+        each character in the <parameter>string</parameter> will become a
+        separate row of the result.
+        If <parameter>delimiter</parameter> is an empty string, then
+        the <parameter>string</parameter> is treated as a single field.
+        If <parameter>null_string</parameter> is supplied and is
+        not <literal>NULL</literal>, fields matching that string are
+        replaced by <literal>NULL</literal>.
+       </para>
+       <para>
+        <literal>string_to_table('xx~^~yy~^~zz', '~^~', 'yy')</literal>
+        <returnvalue></returnvalue>
+<programlisting>
+ xx
+ NULL
+ zz
+</programlisting>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>strpos</primary>
+        </indexterm>
+        <function>strpos</function> ( <parameter>string</parameter> <type>text</type>, <parameter>substring</parameter> <type>text</type> )
+        <returnvalue>integer</returnvalue>
+       </para>
+       <para>
+        Returns first starting index of the specified <parameter>substring</parameter>
+        within <parameter>string</parameter>, or zero if it's not present.
+        (Same as <literal>position(<parameter>substring</parameter> in
+        <parameter>string</parameter>)</literal>, but note the reversed
+        argument order.)
+       </para>
+       <para>
+        <literal>strpos('high', 'ig')</literal>
+        <returnvalue>2</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>substr</primary>
+        </indexterm>
+        <function>substr</function> ( <parameter>string</parameter> <type>text</type>, <parameter>start</parameter> <type>integer</type> <optional>, <parameter>count</parameter> <type>integer</type> </optional> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Extracts the substring of <parameter>string</parameter> starting at
+        the <parameter>start</parameter>'th character,
+        and extending for <parameter>count</parameter> characters if that is
+        specified.  (Same
+        as <literal>substring(<parameter>string</parameter>
+        from <parameter>start</parameter>
+        for <parameter>count</parameter>)</literal>.)
+       </para>
+       <para>
+        <literal>substr('alphabet', 3)</literal>
+        <returnvalue>phabet</returnvalue>
+       </para>
+       <para>
+        <literal>substr('alphabet', 3, 2)</literal>
+        <returnvalue>ph</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>to_ascii</primary>
+        </indexterm>
+        <function>to_ascii</function> ( <parameter>string</parameter> <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para role="func_signature">
+        <function>to_ascii</function> ( <parameter>string</parameter> <type>text</type>,
+        <parameter>encoding</parameter> <type>name</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para role="func_signature">
+        <function>to_ascii</function> ( <parameter>string</parameter> <type>text</type>,
+        <parameter>encoding</parameter> <type>integer</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts <parameter>string</parameter> to <acronym>ASCII</acronym>
+        from another encoding, which may be identified by name or number.
+        If <parameter>encoding</parameter> is omitted the database encoding
+        is assumed (which in practice is the only useful case).
+        The conversion consists primarily of dropping accents.
+        Conversion is only supported
+        from <literal>LATIN1</literal>, <literal>LATIN2</literal>,
+        <literal>LATIN9</literal>, and <literal>WIN1250</literal> encodings.
+        (See the <xref linkend="unaccent"/> module for another, more flexible
+        solution.)
+       </para>
+       <para>
+        <literal>to_ascii('Kar&eacute;l')</literal>
+        <returnvalue>Karel</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>to_bin</primary>
+        </indexterm>
+        <function>to_bin</function> ( <type>integer</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para role="func_signature">
+        <function>to_bin</function> ( <type>bigint</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the number to its equivalent two's complement binary
+        representation.
+       </para>
+       <para>
+        <literal>to_bin(2147483647)</literal>
+        <returnvalue>1111111111111111111111111111111</returnvalue>
+       </para>
+       <para>
+        <literal>to_bin(-1234)</literal>
+        <returnvalue>11111111111111111111101100101110</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>to_hex</primary>
+        </indexterm>
+        <function>to_hex</function> ( <type>integer</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para role="func_signature">
+        <function>to_hex</function> ( <type>bigint</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the number to its equivalent two's complement hexadecimal
+        representation.
+       </para>
+       <para>
+        <literal>to_hex(2147483647)</literal>
+        <returnvalue>7fffffff</returnvalue>
+       </para>
+       <para>
+        <literal>to_hex(-1234)</literal>
+        <returnvalue>fffffb2e</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>to_oct</primary>
+        </indexterm>
+        <function>to_oct</function> ( <type>integer</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para role="func_signature">
+        <function>to_oct</function> ( <type>bigint</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Converts the number to its equivalent two's complement octal
+        representation.
+       </para>
+       <para>
+        <literal>to_oct(2147483647)</literal>
+        <returnvalue>17777777777</returnvalue>
+       </para>
+       <para>
+        <literal>to_oct(-1234)</literal>
+        <returnvalue>37777775456</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>translate</primary>
+        </indexterm>
+        <function>translate</function> ( <parameter>string</parameter> <type>text</type>,
+        <parameter>from</parameter> <type>text</type>,
+        <parameter>to</parameter> <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Replaces each character in <parameter>string</parameter> that
+        matches a character in the <parameter>from</parameter> set with the
+        corresponding character in the <parameter>to</parameter>
+        set. If <parameter>from</parameter> is longer than
+        <parameter>to</parameter>, occurrences of the extra characters in
+        <parameter>from</parameter> are deleted.
+       </para>
+       <para>
+        <literal>translate('12345', '143', 'ax')</literal>
+        <returnvalue>a2x5</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>unistr</primary>
+        </indexterm>
+        <function>unistr</function> ( <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Evaluate escaped Unicode characters in the argument.  Unicode characters
+        can be specified as
+        <literal>\<replaceable>XXXX</replaceable></literal> (4 hexadecimal
+        digits), <literal>\+<replaceable>XXXXXX</replaceable></literal> (6
+        hexadecimal digits),
+        <literal>\u<replaceable>XXXX</replaceable></literal> (4 hexadecimal
+        digits), or <literal>\U<replaceable>XXXXXXXX</replaceable></literal>
+        (8 hexadecimal digits).  To specify a backslash, write two
+        backslashes.  All other characters are taken literally.
+       </para>
+
+       <para>
+        If the server encoding is not UTF-8, the Unicode code point identified
+        by one of these escape sequences is converted to the actual server
+        encoding; an error is reported if that's not possible.
+       </para>
+
+       <para>
+        This function provides a (non-standard) alternative to string
+        constants with Unicode escapes (see <xref
+        linkend="sql-syntax-strings-uescape"/>).
+       </para>
+
+       <para>
+        <literal>unistr('d\0061t\+000061')</literal>
+        <returnvalue>data</returnvalue>
+       </para>
+       <para>
+        <literal>unistr('d\u0061t\U00000061')</literal>
+        <returnvalue>data</returnvalue>
+       </para></entry>
+      </row>
+
+     </tbody>
+    </tgroup>
+   </table>
+
+   <para>
+    The <function>concat</function>, <function>concat_ws</function> and
+    <function>format</function> functions are variadic, so it is possible to
+    pass the values to be concatenated or formatted as an array marked with
+    the <literal>VARIADIC</literal> keyword (see <xref
+    linkend="xfunc-sql-variadic-functions"/>).  The array's elements are
+    treated as if they were separate ordinary arguments to the function.
+    If the variadic array argument is NULL, <function>concat</function>
+    and <function>concat_ws</function> return NULL, but
+    <function>format</function> treats a NULL as a zero-element array.
+   </para>
+
+   <para>
+    See also the aggregate function <function>string_agg</function> in
+    <xref linkend="functions-aggregate"/>, and the functions for
+    converting between strings and the <type>bytea</type> type in
+    <xref linkend="functions-binarystring-conversions"/>.
+   </para>
+
+   <sect2 id="functions-string-format">
+    <title><function>format</function></title>
+
+    <indexterm>
+     <primary>format</primary>
+    </indexterm>
+
+    <para>
+     The function <function>format</function> produces output formatted according to
+     a format string, in a style similar to the C function
+     <function>sprintf</function>.
+    </para>
+
+    <para>
+<synopsis>
+<function>format</function>(<parameter>formatstr</parameter> <type>text</type> <optional>, <parameter>formatarg</parameter> <type>"any"</type> <optional>, ...</optional> </optional>)
+</synopsis>
+     <parameter>formatstr</parameter> is a format string that specifies how the
+     result should be formatted.  Text in the format string is copied
+     directly to the result, except where <firstterm>format specifiers</firstterm> are
+     used.  Format specifiers act as placeholders in the string, defining how
+     subsequent function arguments should be formatted and inserted into the
+     result.  Each <parameter>formatarg</parameter> argument is converted to text
+     according to the usual output rules for its data type, and then formatted
+     and inserted into the result string according to the format specifier(s).
+    </para>
+
+    <para>
+     Format specifiers are introduced by a <literal>%</literal> character and have
+     the form
+<synopsis>
+%[<parameter>position</parameter>][<parameter>flags</parameter>][<parameter>width</parameter>]<parameter>type</parameter>
+</synopsis>
+     where the component fields are:
+
+     <variablelist>
+      <varlistentry>
+       <term><parameter>position</parameter> (optional)</term>
+       <listitem>
+        <para>
+         A string of the form <literal><parameter>n</parameter>$</literal> where
+         <parameter>n</parameter> is the index of the argument to print.
+         Index 1 means the first argument after
+         <parameter>formatstr</parameter>.  If the <parameter>position</parameter> is
+         omitted, the default is to use the next argument in sequence.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term><parameter>flags</parameter> (optional)</term>
+       <listitem>
+        <para>
+         Additional options controlling how the format specifier's output is
+         formatted.  Currently the only supported flag is a minus sign
+         (<literal>-</literal>) which will cause the format specifier's output to be
+         left-justified.  This has no effect unless the <parameter>width</parameter>
+         field is also specified.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term><parameter>width</parameter> (optional)</term>
+       <listitem>
+        <para>
+         Specifies the <emphasis>minimum</emphasis> number of characters to use to
+         display the format specifier's output.  The output is padded on the
+         left or right (depending on the <literal>-</literal> flag) with spaces as
+         needed to fill the width.  A too-small width does not cause
+         truncation of the output, but is simply ignored.  The width may be
+         specified using any of the following: a positive integer; an
+         asterisk (<literal>*</literal>) to use the next function argument as the
+         width; or a string of the form <literal>*<parameter>n</parameter>$</literal> to
+         use the <parameter>n</parameter>th function argument as the width.
+        </para>
+
+        <para>
+         If the width comes from a function argument, that argument is
+         consumed before the argument that is used for the format specifier's
+         value.  If the width argument is negative, the result is left
+         aligned (as if the <literal>-</literal> flag had been specified) within a
+         field of length <function>abs</function>(<parameter>width</parameter>).
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term><parameter>type</parameter> (required)</term>
+       <listitem>
+        <para>
+         The type of format conversion to use to produce the format
+         specifier's output.  The following types are supported:
+         <itemizedlist>
+          <listitem>
+           <para>
+            <literal>s</literal> formats the argument value as a simple
+            string.  A null value is treated as an empty string.
+           </para>
+          </listitem>
+          <listitem>
+           <para>
+            <literal>I</literal> treats the argument value as an SQL
+            identifier, double-quoting it if necessary.
+            It is an error for the value to be null (equivalent to
+            <function>quote_ident</function>).
+           </para>
+          </listitem>
+          <listitem>
+           <para>
+            <literal>L</literal> quotes the argument value as an SQL literal.
+            A null value is displayed as the string <literal>NULL</literal>, without
+            quotes (equivalent to <function>quote_nullable</function>).
+           </para>
+          </listitem>
+         </itemizedlist>
+        </para>
+       </listitem>
+      </varlistentry>
+     </variablelist>
+    </para>
+
+    <para>
+     In addition to the format specifiers described above, the special sequence
+     <literal>%%</literal> may be used to output a literal <literal>%</literal> character.
+    </para>
+
+    <para>
+     Here are some examples of the basic format conversions:
+
+<screen>
+SELECT format('Hello %s', 'World');
+<lineannotation>Result: </lineannotation><computeroutput>Hello World</computeroutput>
+
+SELECT format('Testing %s, %s, %s, %%', 'one', 'two', 'three');
+<lineannotation>Result: </lineannotation><computeroutput>Testing one, two, three, %</computeroutput>
+
+SELECT format('INSERT INTO %I VALUES(%L)', 'Foo bar', E'O\'Reilly');
+<lineannotation>Result: </lineannotation><computeroutput>INSERT INTO "Foo bar" VALUES('O''Reilly')</computeroutput>
+
+SELECT format('INSERT INTO %I VALUES(%L)', 'locations', 'C:\Program Files');
+<lineannotation>Result: </lineannotation><computeroutput>INSERT INTO locations VALUES('C:\Program Files')</computeroutput>
+</screen>
+    </para>
+
+    <para>
+     Here are examples using <parameter>width</parameter> fields
+     and the <literal>-</literal> flag:
+
+<screen>
+SELECT format('|%10s|', 'foo');
+<lineannotation>Result: </lineannotation><computeroutput>|       foo|</computeroutput>
+
+SELECT format('|%-10s|', 'foo');
+<lineannotation>Result: </lineannotation><computeroutput>|foo       |</computeroutput>
+
+SELECT format('|%*s|', 10, 'foo');
+<lineannotation>Result: </lineannotation><computeroutput>|       foo|</computeroutput>
+
+SELECT format('|%*s|', -10, 'foo');
+<lineannotation>Result: </lineannotation><computeroutput>|foo       |</computeroutput>
+
+SELECT format('|%-*s|', 10, 'foo');
+<lineannotation>Result: </lineannotation><computeroutput>|foo       |</computeroutput>
+
+SELECT format('|%-*s|', -10, 'foo');
+<lineannotation>Result: </lineannotation><computeroutput>|foo       |</computeroutput>
+</screen>
+    </para>
+
+    <para>
+     These examples show use of <parameter>position</parameter> fields:
+
+<screen>
+SELECT format('Testing %3$s, %2$s, %1$s', 'one', 'two', 'three');
+<lineannotation>Result: </lineannotation><computeroutput>Testing three, two, one</computeroutput>
+
+SELECT format('|%*2$s|', 'foo', 10, 'bar');
+<lineannotation>Result: </lineannotation><computeroutput>|       bar|</computeroutput>
+
+SELECT format('|%1$*2$s|', 'foo', 10, 'bar');
+<lineannotation>Result: </lineannotation><computeroutput>|       foo|</computeroutput>
+</screen>
+    </para>
+
+    <para>
+     Unlike the standard C function <function>sprintf</function>,
+     <productname>PostgreSQL</productname>'s <function>format</function> function allows format
+     specifiers with and without <parameter>position</parameter> fields to be mixed
+     in the same format string.  A format specifier without a
+     <parameter>position</parameter> field always uses the next argument after the
+     last argument consumed.
+     In addition, the <function>format</function> function does not require all
+     function arguments to be used in the format string.
+     For example:
+
+<screen>
+SELECT format('Testing %3$s, %2$s, %s', 'one', 'two', 'three');
+<lineannotation>Result: </lineannotation><computeroutput>Testing three, two, three</computeroutput>
+</screen>
+    </para>
+
+    <para>
+     The <literal>%I</literal> and <literal>%L</literal> format specifiers are particularly
+     useful for safely constructing dynamic SQL statements.  See
+     <xref linkend="plpgsql-quote-literal-example"/>.
+    </para>
+   </sect2>
+
+  </sect1>