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   2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>9.6. Bit String Functions and Operators</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="functions-binarystring.html" title="9.5. Binary String Functions and Operators" /><link rel="next" href="functions-matching.html" title="9.7. Pattern Matching" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">9.6. Bit String Functions and Operators</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="functions-binarystring.html" title="9.5. Binary String Functions and Operators">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="functions.html" title="Chapter 9. Functions and Operators">Up</a></td><th width="60%" align="center">Chapter 9. Functions and Operators</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 18.0 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="functions-matching.html" title="9.7. Pattern Matching">Next</a></td></tr></table><hr /></div><div class="sect1" id="FUNCTIONS-BITSTRING"><div class="titlepage"><div><div><h2 class="title" style="clear: both">9.6. Bit String Functions and Operators <a href="#FUNCTIONS-BITSTRING" class="id_link">#</a></h2></div></div></div><a id="id-1.5.8.12.2" class="indexterm"></a><p>
   3     This section describes functions and operators for examining and
   4     manipulating bit strings, that is values of the types
   5     <code class="type">bit</code> and <code class="type">bit varying</code>.  (While only
   6     type <code class="type">bit</code> is mentioned in these tables, values of
   7     type <code class="type">bit varying</code> can be used interchangeably.)
   8     Bit strings support the usual comparison operators shown in
   9     <a class="xref" href="functions-comparison.html#FUNCTIONS-COMPARISON-OP-TABLE" title="Table 9.1. Comparison Operators">Table 9.1</a>, as well as the
  10     operators shown in <a class="xref" href="functions-bitstring.html#FUNCTIONS-BIT-STRING-OP-TABLE" title="Table 9.14. Bit String Operators">Table 9.14</a>.
  11    </p><div class="table" id="FUNCTIONS-BIT-STRING-OP-TABLE"><p class="title"><strong>Table 9.14. Bit String Operators</strong></p><div class="table-contents"><table class="table" summary="Bit String Operators" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
  12         Operator
  13        </p>
  14        <p>
  15         Description
  16        </p>
  17        <p>
  18         Example(s)
  19        </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
  20         <code class="type">bit</code> <code class="literal">||</code> <code class="type">bit</code>
  21         → <code class="returnvalue">bit</code>
  22        </p>
  23        <p>
  24         Concatenation
  25        </p>
  26        <p>
  27         <code class="literal">B'10001' || B'011'</code>
  28         → <code class="returnvalue">10001011</code>
  29        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
  30         <code class="type">bit</code> <code class="literal">&amp;</code> <code class="type">bit</code>
  31         → <code class="returnvalue">bit</code>
  32        </p>
  33        <p>
  34         Bitwise AND (inputs must be of equal length)
  35        </p>
  36        <p>
  37         <code class="literal">B'10001' &amp; B'01101'</code>
  38         → <code class="returnvalue">00001</code>
  39        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
  40         <code class="type">bit</code> <code class="literal">|</code> <code class="type">bit</code>
  41         → <code class="returnvalue">bit</code>
  42        </p>
  43        <p>
  44         Bitwise OR (inputs must be of equal length)
  45        </p>
  46        <p>
  47         <code class="literal">B'10001' | B'01101'</code>
  48         → <code class="returnvalue">11101</code>
  49        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
  50         <code class="type">bit</code> <code class="literal">#</code> <code class="type">bit</code>
  51         → <code class="returnvalue">bit</code>
  52        </p>
  53        <p>
  54         Bitwise exclusive OR (inputs must be of equal length)
  55        </p>
  56        <p>
  57         <code class="literal">B'10001' # B'01101'</code>
  58         → <code class="returnvalue">11100</code>
  59        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
  60         <code class="literal">~</code> <code class="type">bit</code>
  61         → <code class="returnvalue">bit</code>
  62        </p>
  63        <p>
  64         Bitwise NOT
  65        </p>
  66        <p>
  67         <code class="literal">~ B'10001'</code>
  68         → <code class="returnvalue">01110</code>
  69        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
  70         <code class="type">bit</code> <code class="literal">&lt;&lt;</code> <code class="type">integer</code>
  71         → <code class="returnvalue">bit</code>
  72        </p>
  73        <p>
  74         Bitwise shift left
  75         (string length is preserved)
  76        </p>
  77        <p>
  78         <code class="literal">B'10001' &lt;&lt; 3</code>
  79         → <code class="returnvalue">01000</code>
  80        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
  81         <code class="type">bit</code> <code class="literal">&gt;&gt;</code> <code class="type">integer</code>
  82         → <code class="returnvalue">bit</code>
  83        </p>
  84        <p>
  85         Bitwise shift right
  86         (string length is preserved)
  87        </p>
  88        <p>
  89         <code class="literal">B'10001' &gt;&gt; 2</code>
  90         → <code class="returnvalue">00100</code>
  91        </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
  92     Some of the functions available for binary strings are also available
  93     for bit strings, as shown in <a class="xref" href="functions-bitstring.html#FUNCTIONS-BIT-STRING-TABLE" title="Table 9.15. Bit String Functions">Table 9.15</a>.
  94    </p><div class="table" id="FUNCTIONS-BIT-STRING-TABLE"><p class="title"><strong>Table 9.15. Bit String Functions</strong></p><div class="table-contents"><table class="table" summary="Bit String Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
  95         Function
  96        </p>
  97        <p>
  98         Description
  99        </p>
 100        <p>
 101         Example(s)
 102        </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
 103         <a id="id-1.5.8.12.6.2.2.1.1.1.1" class="indexterm"></a>
 104         <code class="function">bit_count</code> ( <code class="type">bit</code> )
 105         → <code class="returnvalue">bigint</code>
 106        </p>
 107        <p>
 108         Returns the number of bits set in the bit string (also known as
 109         <span class="quote">“<span class="quote">popcount</span>”</span>).
 110        </p>
 111        <p>
 112         <code class="literal">bit_count(B'10111')</code>
 113         → <code class="returnvalue">4</code>
 114        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
 115         <a id="id-1.5.8.12.6.2.2.2.1.1.1" class="indexterm"></a>
 116         <code class="function">bit_length</code> ( <code class="type">bit</code> )
 117         → <code class="returnvalue">integer</code>
 118        </p>
 119        <p>
 120         Returns number of bits in the bit string.
 121        </p>
 122        <p>
 123         <code class="literal">bit_length(B'10111')</code>
 124         → <code class="returnvalue">5</code>
 125        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
 126         <a id="id-1.5.8.12.6.2.2.3.1.1.1" class="indexterm"></a>
 127         <a id="id-1.5.8.12.6.2.2.3.1.1.2" class="indexterm"></a>
 128         <code class="function">length</code> ( <code class="type">bit</code> )
 129         → <code class="returnvalue">integer</code>
 130        </p>
 131        <p>
 132         Returns number of bits in the bit string.
 133        </p>
 134        <p>
 135         <code class="literal">length(B'10111')</code>
 136         → <code class="returnvalue">5</code>
 137        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
 138         <a id="id-1.5.8.12.6.2.2.4.1.1.1" class="indexterm"></a>
 139         <code class="function">octet_length</code> ( <code class="type">bit</code> )
 140         → <code class="returnvalue">integer</code>
 141        </p>
 142        <p>
 143         Returns number of bytes in the bit string.
 144        </p>
 145        <p>
 146         <code class="literal">octet_length(B'1011111011')</code>
 147         → <code class="returnvalue">2</code>
 148        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
 149         <a id="id-1.5.8.12.6.2.2.5.1.1.1" class="indexterm"></a>
 150         <code class="function">overlay</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code> <code class="literal">PLACING</code> <em class="parameter"><code>newsubstring</code></em> <code class="type">bit</code> <code class="literal">FROM</code> <em class="parameter"><code>start</code></em> <code class="type">integer</code> [<span class="optional"> <code class="literal">FOR</code> <em class="parameter"><code>count</code></em> <code class="type">integer</code> </span>] )
 151         → <code class="returnvalue">bit</code>
 152        </p>
 153        <p>
 154         Replaces the substring of <em class="parameter"><code>bits</code></em> that starts at
 155         the <em class="parameter"><code>start</code></em>'th bit and extends
 156         for <em class="parameter"><code>count</code></em> bits
 157         with <em class="parameter"><code>newsubstring</code></em>.
 158         If <em class="parameter"><code>count</code></em> is omitted, it defaults to the length
 159         of <em class="parameter"><code>newsubstring</code></em>.
 160        </p>
 161        <p>
 162         <code class="literal">overlay(B'01010101010101010' placing B'11111' from 2 for 3)</code>
 163         → <code class="returnvalue">0111110101010101010</code>
 164        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
 165         <a id="id-1.5.8.12.6.2.2.6.1.1.1" class="indexterm"></a>
 166         <code class="function">position</code> ( <em class="parameter"><code>substring</code></em> <code class="type">bit</code> <code class="literal">IN</code> <em class="parameter"><code>bits</code></em> <code class="type">bit</code> )
 167         → <code class="returnvalue">integer</code>
 168        </p>
 169        <p>
 170         Returns first starting index of the specified <em class="parameter"><code>substring</code></em>
 171         within <em class="parameter"><code>bits</code></em>, or zero if it's not present.
 172        </p>
 173        <p>
 174         <code class="literal">position(B'010' in B'000001101011')</code>
 175         → <code class="returnvalue">8</code>
 176        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
 177         <a id="id-1.5.8.12.6.2.2.7.1.1.1" class="indexterm"></a>
 178         <code class="function">substring</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code> [<span class="optional"> <code class="literal">FROM</code> <em class="parameter"><code>start</code></em> <code class="type">integer</code> </span>] [<span class="optional"> <code class="literal">FOR</code> <em class="parameter"><code>count</code></em> <code class="type">integer</code> </span>] )
 179         → <code class="returnvalue">bit</code>
 180        </p>
 181        <p>
 182         Extracts the substring of <em class="parameter"><code>bits</code></em> starting at
 183         the <em class="parameter"><code>start</code></em>'th bit if that is specified,
 184         and stopping after <em class="parameter"><code>count</code></em> bits if that is
 185         specified.  Provide at least one of <em class="parameter"><code>start</code></em>
 186         and <em class="parameter"><code>count</code></em>.
 187        </p>
 188        <p>
 189         <code class="literal">substring(B'110010111111' from 3 for 2)</code>
 190         → <code class="returnvalue">00</code>
 191        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
 192         <a id="id-1.5.8.12.6.2.2.8.1.1.1" class="indexterm"></a>
 193         <code class="function">get_bit</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code>,
 194         <em class="parameter"><code>n</code></em> <code class="type">integer</code> )
 195         → <code class="returnvalue">integer</code>
 196        </p>
 197        <p>
 198         Extracts <em class="parameter"><code>n</code></em>'th bit
 199         from bit string; the first (leftmost) bit is bit 0.
 200        </p>
 201        <p>
 202         <code class="literal">get_bit(B'101010101010101010', 6)</code>
 203         → <code class="returnvalue">1</code>
 204        </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
 205         <a id="id-1.5.8.12.6.2.2.9.1.1.1" class="indexterm"></a>
 206         <code class="function">set_bit</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code>,
 207         <em class="parameter"><code>n</code></em> <code class="type">integer</code>,
 208         <em class="parameter"><code>newvalue</code></em> <code class="type">integer</code> )
 209         → <code class="returnvalue">bit</code>
 210        </p>
 211        <p>
 212         Sets <em class="parameter"><code>n</code></em>'th bit in
 213         bit string to <em class="parameter"><code>newvalue</code></em>;
 214         the first (leftmost) bit is bit 0.
 215        </p>
 216        <p>
 217         <code class="literal">set_bit(B'101010101010101010', 6, 0)</code>
 218         → <code class="returnvalue">101010001010101010</code>
 219        </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
 220     In addition, it is possible to cast integral values to and from type
 221     <code class="type">bit</code>.
 222     Casting an integer to <code class="type">bit(n)</code> copies the rightmost
 223     <code class="literal">n</code> bits.  Casting an integer to a bit string width wider
 224     than the integer itself will sign-extend on the left.
 225     Some examples:
 226 </p><pre class="programlisting">
 227 44::bit(10)                    <em class="lineannotation"><span class="lineannotation">0000101100</span></em>
 228 44::bit(3)                     <em class="lineannotation"><span class="lineannotation">100</span></em>
 229 cast(-44 as bit(12))           <em class="lineannotation"><span class="lineannotation">111111010100</span></em>
 230 '1110'::bit(4)::integer        <em class="lineannotation"><span class="lineannotation">14</span></em>
 231 </pre><p>
 232     Note that casting to just <span class="quote">“<span class="quote">bit</span>”</span> means casting to
 233     <code class="literal">bit(1)</code>, and so will deliver only the least significant
 234     bit of the integer.
 235    </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="functions-binarystring.html" title="9.5. Binary String Functions and Operators">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="functions.html" title="Chapter 9. Functions and Operators">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="functions-matching.html" title="9.7. Pattern Matching">Next</a></td></tr><tr><td width="40%" align="left" valign="top">9.5. Binary String Functions and Operators </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 18.0 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 9.7. Pattern Matching</td></tr></table></div></body></html>