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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!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 15.7 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</h2></div></div></div><a id="id-1.5.8.12.2" class="indexterm"></a><p>
This section describes functions and operators for examining and
manipulating bit strings, that is values of the types
<code class="type">bit</code> and <code class="type">bit varying</code>. (While only
type <code class="type">bit</code> is mentioned in these tables, values of
type <code class="type">bit varying</code> can be used interchangeably.)
Bit strings support the usual comparison operators shown in
<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
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>.
</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">
Operator
</p>
<p>
Description
</p>
<p>
Example(s)
</p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">bit</code> <code class="literal">||</code> <code class="type">bit</code>
→ <code class="returnvalue">bit</code>
</p>
<p>
Concatenation
</p>
<p>
<code class="literal">B'10001' || B'011'</code>
→ <code class="returnvalue">10001011</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">bit</code> <code class="literal">&</code> <code class="type">bit</code>
→ <code class="returnvalue">bit</code>
</p>
<p>
Bitwise AND (inputs must be of equal length)
</p>
<p>
<code class="literal">B'10001' & B'01101'</code>
→ <code class="returnvalue">00001</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">bit</code> <code class="literal">|</code> <code class="type">bit</code>
→ <code class="returnvalue">bit</code>
</p>
<p>
Bitwise OR (inputs must be of equal length)
</p>
<p>
<code class="literal">B'10001' | B'01101'</code>
→ <code class="returnvalue">11101</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">bit</code> <code class="literal">#</code> <code class="type">bit</code>
→ <code class="returnvalue">bit</code>
</p>
<p>
Bitwise exclusive OR (inputs must be of equal length)
</p>
<p>
<code class="literal">B'10001' # B'01101'</code>
→ <code class="returnvalue">11100</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="literal">~</code> <code class="type">bit</code>
→ <code class="returnvalue">bit</code>
</p>
<p>
Bitwise NOT
</p>
<p>
<code class="literal">~ B'10001'</code>
→ <code class="returnvalue">01110</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">bit</code> <code class="literal"><<</code> <code class="type">integer</code>
→ <code class="returnvalue">bit</code>
</p>
<p>
Bitwise shift left
(string length is preserved)
</p>
<p>
<code class="literal">B'10001' << 3</code>
→ <code class="returnvalue">01000</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">bit</code> <code class="literal">>></code> <code class="type">integer</code>
→ <code class="returnvalue">bit</code>
</p>
<p>
Bitwise shift right
(string length is preserved)
</p>
<p>
<code class="literal">B'10001' >> 2</code>
→ <code class="returnvalue">00100</code>
</p></td></tr></tbody></table></div></div><br class="table-break" /><p>
Some of the functions available for binary strings are also available
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>.
</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">
Function
</p>
<p>
Description
</p>
<p>
Example(s)
</p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.12.6.2.2.1.1.1.1" class="indexterm"></a>
<code class="function">bit_count</code> ( <code class="type">bit</code> )
→ <code class="returnvalue">bigint</code>
</p>
<p>
Returns the number of bits set in the bit string (also known as
<span class="quote">“<span class="quote">popcount</span>”</span>).
</p>
<p>
<code class="literal">bit_count(B'10111')</code>
→ <code class="returnvalue">4</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.12.6.2.2.2.1.1.1" class="indexterm"></a>
<code class="function">bit_length</code> ( <code class="type">bit</code> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns number of bits in the bit string.
</p>
<p>
<code class="literal">bit_length(B'10111')</code>
→ <code class="returnvalue">5</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.12.6.2.2.3.1.1.1" class="indexterm"></a>
<a id="id-1.5.8.12.6.2.2.3.1.1.2" class="indexterm"></a>
<code class="function">length</code> ( <code class="type">bit</code> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns number of bits in the bit string.
</p>
<p>
<code class="literal">length(B'10111')</code>
→ <code class="returnvalue">5</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.12.6.2.2.4.1.1.1" class="indexterm"></a>
<code class="function">octet_length</code> ( <code class="type">bit</code> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns number of bytes in the bit string.
</p>
<p>
<code class="literal">octet_length(B'1011111011')</code>
→ <code class="returnvalue">2</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.12.6.2.2.5.1.1.1" class="indexterm"></a>
<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>] )
→ <code class="returnvalue">bit</code>
</p>
<p>
Replaces the substring of <em class="parameter"><code>bits</code></em> that starts at
the <em class="parameter"><code>start</code></em>'th bit and extends
for <em class="parameter"><code>count</code></em> bits
with <em class="parameter"><code>newsubstring</code></em>.
If <em class="parameter"><code>count</code></em> is omitted, it defaults to the length
of <em class="parameter"><code>newsubstring</code></em>.
</p>
<p>
<code class="literal">overlay(B'01010101010101010' placing B'11111' from 2 for 3)</code>
→ <code class="returnvalue">0111110101010101010</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.12.6.2.2.6.1.1.1" class="indexterm"></a>
<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> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Returns first starting index of the specified <em class="parameter"><code>substring</code></em>
within <em class="parameter"><code>bits</code></em>, or zero if it's not present.
</p>
<p>
<code class="literal">position(B'010' in B'000001101011')</code>
→ <code class="returnvalue">8</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.12.6.2.2.7.1.1.1" class="indexterm"></a>
<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>] )
→ <code class="returnvalue">bit</code>
</p>
<p>
Extracts the substring of <em class="parameter"><code>bits</code></em> starting at
the <em class="parameter"><code>start</code></em>'th bit if that is specified,
and stopping after <em class="parameter"><code>count</code></em> bits if that is
specified. Provide at least one of <em class="parameter"><code>start</code></em>
and <em class="parameter"><code>count</code></em>.
</p>
<p>
<code class="literal">substring(B'110010111111' from 3 for 2)</code>
→ <code class="returnvalue">00</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.12.6.2.2.8.1.1.1" class="indexterm"></a>
<code class="function">get_bit</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code>,
<em class="parameter"><code>n</code></em> <code class="type">integer</code> )
→ <code class="returnvalue">integer</code>
</p>
<p>
Extracts <em class="parameter"><code>n</code></em>'th bit
from bit string; the first (leftmost) bit is bit 0.
</p>
<p>
<code class="literal">get_bit(B'101010101010101010', 6)</code>
→ <code class="returnvalue">1</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.5.8.12.6.2.2.9.1.1.1" class="indexterm"></a>
<code class="function">set_bit</code> ( <em class="parameter"><code>bits</code></em> <code class="type">bit</code>,
<em class="parameter"><code>n</code></em> <code class="type">integer</code>,
<em class="parameter"><code>newvalue</code></em> <code class="type">integer</code> )
→ <code class="returnvalue">bit</code>
</p>
<p>
Sets <em class="parameter"><code>n</code></em>'th bit in
bit string to <em class="parameter"><code>newvalue</code></em>;
the first (leftmost) bit is bit 0.
</p>
<p>
<code class="literal">set_bit(B'101010101010101010', 6, 0)</code>
→ <code class="returnvalue">101010001010101010</code>
</p></td></tr></tbody></table></div></div><br class="table-break" /><p>
In addition, it is possible to cast integral values to and from type
<code class="type">bit</code>.
Casting an integer to <code class="type">bit(n)</code> copies the rightmost
<code class="literal">n</code> bits. Casting an integer to a bit string width wider
than the integer itself will sign-extend on the left.
Some examples:
</p><pre class="programlisting">
44::bit(10) <em class="lineannotation"><span class="lineannotation">0000101100</span></em>
44::bit(3) <em class="lineannotation"><span class="lineannotation">100</span></em>
cast(-44 as bit(12)) <em class="lineannotation"><span class="lineannotation">111111010100</span></em>
'1110'::bit(4)::integer <em class="lineannotation"><span class="lineannotation">14</span></em>
</pre><p>
Note that casting to just <span class="quote">“<span class="quote">bit</span>”</span> means casting to
<code class="literal">bit(1)</code>, and so will deliver only the least significant
bit of the integer.
</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 15.7 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 9.7. Pattern Matching</td></tr></table></div></body></html>
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